draft-lafon-rfc2616bis-00.txt   draft-lafon-rfc2616bis-01.txt 
Network Working Group Y. Lafon Network Working Group R. Fielding
Internet-Draft W3C Internet-Draft Day Software
Obsoletes: 2616 (if approved) J. Reschke Obsoletes: 2616 (if approved) J. Gettys
Intended status: Standards Track greenbytes Intended status: Standards Track J. Mogul
Expires: April 16, 2007 October 13, 2006 Expires: April 25, 2007 HP
H. Frystyk
Microsoft
L. Masinter
Adobe Systems
P. Leach
Microsoft
T. Berners-Lee
W3C/MIT
Y. Lafon, Ed.
W3C
J. Reschke, Ed.
greenbytes
October 22, 2006
Hypertext Transfer Protocol -- HTTP/1.1 Hypertext Transfer Protocol -- HTTP/1.1
draft-lafon-rfc2616bis-00 draft-lafon-rfc2616bis-01
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 35 skipping to change at page 1, line 48
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 16, 2007. This Internet-Draft will expire on April 25, 2007.
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information protocol for distributed, collaborative, hypermedia information
systems. It is a generic, stateless, protocol which can be used for systems. It is a generic, stateless, protocol which can be used for
many tasks beyond its use for hypertext, such as name servers and many tasks beyond its use for hypertext, such as name servers and
distributed object management systems, through extension of its distributed object management systems, through extension of its
request methods, error codes and headers [47]. A feature of HTTP is request methods, error codes and headers [47]. A feature of HTTP is
the typing and negotiation of data representation, allowing systems the typing and negotiation of data representation, allowing systems
skipping to change at page 3, line 26 skipping to change at page 3, line 26
The purpose of this document is to revise RFC2616 ([50]), doing only The purpose of this document is to revise RFC2616 ([50]), doing only
minimal corrections. For now, it is not planned to advance the minimal corrections. For now, it is not planned to advance the
standards level of HTTP, thus - if published - the specification will standards level of HTTP, thus - if published - the specification will
still be a "Proposed Standard" (see [46]). still be a "Proposed Standard" (see [46]).
The current plan is to incorporate known errata, and to update the The current plan is to incorporate known errata, and to update the
specification text according to the current IETF publication specification text according to the current IETF publication
guidelines. In particular: guidelines. In particular:
o Incorporate the corrections collected in the RFC2616 errata o Incorporate the corrections collected in the RFC2616 errata
document (<http://skrb.org/ietf/http_errata.html>) and potentially document (<http://purl.org/NET/http-errata>) (most of the
newly discovered and agreed-upon errata. suggested fixes have been applied to draft 01).
o Incorporate corrections for newly discovered and agreed-upon
problems, using the HTTP WG mailing list as forum.
o Update references, and re-classify them into "Normative" and o Update references, and re-classify them into "Normative" and
"Informative", based on the prior work done by Jim Gettys in "Informative", based on the prior work done by Jim Gettys in
<http://tools.ietf.org/html/draft-gettys-http-v11-spec-rev-00>. <http://tools.ietf.org/html/draft-gettys-http-v11-spec-rev-00>.
This document is based on a variant of the original RFC2616 This document is based on a variant of the original RFC2616
specification formatted using Marshall T. Rose's "xml2rfc" tool (see specification formatted using Marshall T. Rose's "xml2rfc" tool (see
<http://xml.resource.org>) and therefore deviates from the original <http://xml.resource.org>) and therefore deviates from the original
text in word wrapping, page breaks, list formatting, reference text in word wrapping, page breaks, list formatting, reference
formatting, whitespace usage and appendix numbering. Otherwise, it formatting, whitespace usage and appendix numbering. Otherwise, it
is supposed to contain an accurate copy of the original specification is supposed to contain an accurate copy of the original specification
text. See <http://www.w3.org/Protocols/HTTP/1.1/ text. See <http://www.w3.org/Protocols/HTTP/1.1/
rfc2616bis-00-from-rfc2616.diff.html> for a comparison between both rfc2616bis-00-from-rfc2616.diff.html> for a comparison between both
documents, as generated by "rfcdiff" documents, as generated by "rfcdiff"
(<http://tools.ietf.org/tools/rfcdiff/>). (<http://tools.ietf.org/tools/rfcdiff/>).
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 11
1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . 10 1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 10 1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 11
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . 11 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . 12
1.4. Overall Operation . . . . . . . . . . . . . . . . . . . 15 1.4. Overall Operation . . . . . . . . . . . . . . . . . . . 16
2. Notational Conventions and Generic Grammar . . . . . . . . . 18 2. Notational Conventions and Generic Grammar . . . . . . . . . 19
2.1. Augmented BNF . . . . . . . . . . . . . . . . . . . . . 18 2.1. Augmented BNF . . . . . . . . . . . . . . . . . . . . . 19
2.2. Basic Rules . . . . . . . . . . . . . . . . . . . . . . 20 2.2. Basic Rules . . . . . . . . . . . . . . . . . . . . . . 21
3. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 22 3. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 23
3.1. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 22 3.1. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 23
3.2. Uniform Resource Identifiers . . . . . . . . . . . . . . 23 3.2. Uniform Resource Identifiers . . . . . . . . . . . . . . 24
3.2.1. General Syntax . . . . . . . . . . . . . . . . . . . 23 3.2.1. General Syntax . . . . . . . . . . . . . . . . . . . 24
3.2.2. http URL . . . . . . . . . . . . . . . . . . . . . . 23 3.2.2. http URL . . . . . . . . . . . . . . . . . . . . . . 25
3.2.3. URI Comparison . . . . . . . . . . . . . . . . . . . 24 3.2.3. URI Comparison . . . . . . . . . . . . . . . . . . . 25
3.3. Date/Time Formats . . . . . . . . . . . . . . . . . . . 24 3.3. Date/Time Formats . . . . . . . . . . . . . . . . . . . 26
3.3.1. Full Date . . . . . . . . . . . . . . . . . . . . . 24 3.3.1. Full Date . . . . . . . . . . . . . . . . . . . . . 26
3.3.2. Delta Seconds . . . . . . . . . . . . . . . . . . . 26 3.3.2. Delta Seconds . . . . . . . . . . . . . . . . . . . 27
3.4. Character Sets . . . . . . . . . . . . . . . . . . . . . 26 3.4. Character Sets . . . . . . . . . . . . . . . . . . . . . 27
3.4.1. Missing Charset . . . . . . . . . . . . . . . . . . 27 3.4.1. Missing Charset . . . . . . . . . . . . . . . . . . 28
3.5. Content Codings . . . . . . . . . . . . . . . . . . . . 27 3.5. Content Codings . . . . . . . . . . . . . . . . . . . . 29
3.6. Transfer Codings . . . . . . . . . . . . . . . . . . . . 28 3.6. Transfer Codings . . . . . . . . . . . . . . . . . . . . 30
3.6.1. Chunked Transfer Coding . . . . . . . . . . . . . . 29 3.6.1. Chunked Transfer Coding . . . . . . . . . . . . . . 31
3.7. Media Types . . . . . . . . . . . . . . . . . . . . . . 31 3.7. Media Types . . . . . . . . . . . . . . . . . . . . . . 32
3.7.1. Canonicalization and Text Defaults . . . . . . . . . 31 3.7.1. Canonicalization and Text Defaults . . . . . . . . . 33
3.7.2. Multipart Types . . . . . . . . . . . . . . . . . . 32 3.7.2. Multipart Types . . . . . . . . . . . . . . . . . . 34
3.8. Product Tokens . . . . . . . . . . . . . . . . . . . . . 33 3.8. Product Tokens . . . . . . . . . . . . . . . . . . . . . 34
3.9. Quality Values . . . . . . . . . . . . . . . . . . . . . 33 3.9. Quality Values . . . . . . . . . . . . . . . . . . . . . 35
3.10. Language Tags . . . . . . . . . . . . . . . . . . . . . 34 3.10. Language Tags . . . . . . . . . . . . . . . . . . . . . 35
3.11. Entity Tags . . . . . . . . . . . . . . . . . . . . . . 34 3.11. Entity Tags . . . . . . . . . . . . . . . . . . . . . . 36
3.12. Range Units . . . . . . . . . . . . . . . . . . . . . . 35 3.12. Range Units . . . . . . . . . . . . . . . . . . . . . . 36
4. HTTP Message . . . . . . . . . . . . . . . . . . . . . . . . 36 4. HTTP Message . . . . . . . . . . . . . . . . . . . . . . . . 38
4.1. Message Types . . . . . . . . . . . . . . . . . . . . . 36 4.1. Message Types . . . . . . . . . . . . . . . . . . . . . 38
4.2. Message Headers . . . . . . . . . . . . . . . . . . . . 36 4.2. Message Headers . . . . . . . . . . . . . . . . . . . . 38
4.3. Message Body . . . . . . . . . . . . . . . . . . . . . . 37 4.3. Message Body . . . . . . . . . . . . . . . . . . . . . . 39
4.4. Message Length . . . . . . . . . . . . . . . . . . . . . 38 4.4. Message Length . . . . . . . . . . . . . . . . . . . . . 40
4.5. General Header Fields . . . . . . . . . . . . . . . . . 39 4.5. General Header Fields . . . . . . . . . . . . . . . . . 41
5. Request . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5. Request . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.1. Request-Line . . . . . . . . . . . . . . . . . . . . . . 41 5.1. Request-Line . . . . . . . . . . . . . . . . . . . . . . 43
5.1.1. Method . . . . . . . . . . . . . . . . . . . . . . . 41 5.1.1. Method . . . . . . . . . . . . . . . . . . . . . . . 43
5.1.2. Request-URI . . . . . . . . . . . . . . . . . . . . 42 5.1.2. Request-URI . . . . . . . . . . . . . . . . . . . . 44
5.2. The Resource Identified by a Request . . . . . . . . . . 43 5.2. The Resource Identified by a Request . . . . . . . . . . 45
5.3. Request Header Fields . . . . . . . . . . . . . . . . . 44 5.3. Request Header Fields . . . . . . . . . . . . . . . . . 46
6. Response . . . . . . . . . . . . . . . . . . . . . . . . . . 45 6. Response . . . . . . . . . . . . . . . . . . . . . . . . . . 47
6.1. Status-Line . . . . . . . . . . . . . . . . . . . . . . 45 6.1. Status-Line . . . . . . . . . . . . . . . . . . . . . . 47
6.1.1. Status Code and Reason Phrase . . . . . . . . . . . 45 6.1.1. Status Code and Reason Phrase . . . . . . . . . . . 47
6.2. Response Header Fields . . . . . . . . . . . . . . . . . 48 6.2. Response Header Fields . . . . . . . . . . . . . . . . . 50
7. Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 7. Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.1. Entity Header Fields . . . . . . . . . . . . . . . . . . 49 7.1. Entity Header Fields . . . . . . . . . . . . . . . . . . 51
7.2. Entity Body . . . . . . . . . . . . . . . . . . . . . . 49 7.2. Entity Body . . . . . . . . . . . . . . . . . . . . . . 51
7.2.1. Type . . . . . . . . . . . . . . . . . . . . . . . . 50 7.2.1. Type . . . . . . . . . . . . . . . . . . . . . . . . 52
7.2.2. Entity Length . . . . . . . . . . . . . . . . . . . 50 7.2.2. Entity Length . . . . . . . . . . . . . . . . . . . 52
8. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 51 8. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.1. Persistent Connections . . . . . . . . . . . . . . . . . 51 8.1. Persistent Connections . . . . . . . . . . . . . . . . . 53
8.1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . 51 8.1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . 53
8.1.2. Overall Operation . . . . . . . . . . . . . . . . . 51 8.1.2. Overall Operation . . . . . . . . . . . . . . . . . 53
8.1.3. Proxy Servers . . . . . . . . . . . . . . . . . . . 53 8.1.3. Proxy Servers . . . . . . . . . . . . . . . . . . . 55
8.1.4. Practical Considerations . . . . . . . . . . . . . . 53 8.1.4. Practical Considerations . . . . . . . . . . . . . . 55
8.2. Message Transmission Requirements . . . . . . . . . . . 54 8.2. Message Transmission Requirements . . . . . . . . . . . 56
8.2.1. Persistent Connections and Flow Control . . . . . . 54 8.2.1. Persistent Connections and Flow Control . . . . . . 56
8.2.2. Monitoring Connections for Error Status Messages . . 54 8.2.2. Monitoring Connections for Error Status Messages . . 56
8.2.3. Use of the 100 (Continue) Status . . . . . . . . . . 55 8.2.3. Use of the 100 (Continue) Status . . . . . . . . . . 57
8.2.4. Client Behavior if Server Prematurely Closes 8.2.4. Client Behavior if Server Prematurely Closes
Connection . . . . . . . . . . . . . . . . . . . . . 57 Connection . . . . . . . . . . . . . . . . . . . . . 59
9. Method Definitions . . . . . . . . . . . . . . . . . . . . . 58 9. Method Definitions . . . . . . . . . . . . . . . . . . . . . 60
9.1. Safe and Idempotent Methods . . . . . . . . . . . . . . 58 9.1. Safe and Idempotent Methods . . . . . . . . . . . . . . 60
9.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . 58 9.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . 60
9.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . 58 9.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . 60
9.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . 59 9.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . 61
9.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . 60 9.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . 62
9.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . 60 9.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . 62
9.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . 61 9.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . 63
9.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . 62 9.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . 63 9.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . 63 9.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . 64 9.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . 66
10. Status Code Definitions . . . . . . . . . . . . . . . . . . . 65 10. Status Code Definitions . . . . . . . . . . . . . . . . . . . 67
10.1. Informational 1xx . . . . . . . . . . . . . . . . . . . 65 10.1. Informational 1xx . . . . . . . . . . . . . . . . . . . 67
10.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . 65 10.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . 67
10.1.2. 101 Switching Protocols . . . . . . . . . . . . . . 65 10.1.2. 101 Switching Protocols . . . . . . . . . . . . . . 67
10.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . 66 10.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . 68
10.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . 66 10.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . 68
10.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . 66 10.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . 68
10.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . 66 10.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . 68
10.2.4. 203 Non-Authoritative Information . . . . . . . . . 67 10.2.4. 203 Non-Authoritative Information . . . . . . . . . 69
10.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . 67 10.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . 69
10.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . 67 10.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . 69
10.2.7. 206 Partial Content . . . . . . . . . . . . . . . . 68 10.2.7. 206 Partial Content . . . . . . . . . . . . . . . . 70
10.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . 68 10.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . 70
10.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . 69 10.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . 71
10.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . 69 10.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . 71
10.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . 70 10.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . 72
10.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . 70 10.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . 72
10.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . 71 10.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . 73
10.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . 71 10.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . 73
10.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . 72 10.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . 74
10.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . 72 10.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . 74
10.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . 72 10.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . 74
10.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . 73 10.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . 75
10.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . 73 10.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . 75
10.4.3. 402 Payment Required . . . . . . . . . . . . . . . . 73 10.4.3. 402 Payment Required . . . . . . . . . . . . . . . . 75
10.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . 73 10.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . 75
10.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . 73 10.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . 75
10.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . 74 10.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . 76
10.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . 74 10.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . 76
10.4.8. 407 Proxy Authentication Required . . . . . . . . . 74 10.4.8. 407 Proxy Authentication Required . . . . . . . . . 76
10.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . 75 10.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . 77
10.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . 75 10.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . 77
10.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . 75 10.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . 77
10.4.12. 411 Length Required . . . . . . . . . . . . . . . . 76 10.4.12. 411 Length Required . . . . . . . . . . . . . . . . 78
10.4.13. 412 Precondition Failed . . . . . . . . . . . . . . 76 10.4.13. 412 Precondition Failed . . . . . . . . . . . . . . 78
10.4.14. 413 Request Entity Too Large . . . . . . . . . . . . 76 10.4.14. 413 Request Entity Too Large . . . . . . . . . . . . 78
10.4.15. 414 Request-URI Too Long . . . . . . . . . . . . . . 76 10.4.15. 414 Request-URI Too Long . . . . . . . . . . . . . . 78
10.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . 76 10.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . 78
10.4.17. 416 Requested Range Not Satisfiable . . . . . . . . 76 10.4.17. 416 Requested Range Not Satisfiable . . . . . . . . 78
10.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . 77 10.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . 79
10.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . 77 10.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . 79
10.5.1. 500 Internal Server Error . . . . . . . . . . . . . 77 10.5.1. 500 Internal Server Error . . . . . . . . . . . . . 79
10.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . 77 10.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . 79
10.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . 77 10.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . 79
10.5.4. 503 Service Unavailable . . . . . . . . . . . . . . 78 10.5.4. 503 Service Unavailable . . . . . . . . . . . . . . 80
10.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . 78 10.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . 80
10.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . 78 10.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . 80
11. Access Authentication . . . . . . . . . . . . . . . . . . . . 79 11. Access Authentication . . . . . . . . . . . . . . . . . . . . 81
12. Content Negotiation . . . . . . . . . . . . . . . . . . . . . 80 12. Content Negotiation . . . . . . . . . . . . . . . . . . . . . 82
12.1. Server-driven Negotiation . . . . . . . . . . . . . . . 80 12.1. Server-driven Negotiation . . . . . . . . . . . . . . . 82
12.2. Agent-driven Negotiation . . . . . . . . . . . . . . . . 81 12.2. Agent-driven Negotiation . . . . . . . . . . . . . . . . 83
12.3. Transparent Negotiation . . . . . . . . . . . . . . . . 82 12.3. Transparent Negotiation . . . . . . . . . . . . . . . . 84
13. Caching in HTTP . . . . . . . . . . . . . . . . . . . . . . . 83 13. Caching in HTTP . . . . . . . . . . . . . . . . . . . . . . . 85
13.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 13.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
13.1.1. Cache Correctness . . . . . . . . . . . . . . . . . 84 13.1.1. Cache Correctness . . . . . . . . . . . . . . . . . 86
13.1.2. Warnings . . . . . . . . . . . . . . . . . . . . . . 85 13.1.2. Warnings . . . . . . . . . . . . . . . . . . . . . . 87
13.1.3. Cache-control Mechanisms . . . . . . . . . . . . . . 86 13.1.3. Cache-control Mechanisms . . . . . . . . . . . . . . 88
13.1.4. Explicit User Agent Warnings . . . . . . . . . . . . 86 13.1.4. Explicit User Agent Warnings . . . . . . . . . . . . 88
13.1.5. Exceptions to the Rules and Warnings . . . . . . . . 87 13.1.5. Exceptions to the Rules and Warnings . . . . . . . . 89
13.1.6. Client-controlled Behavior . . . . . . . . . . . . . 87 13.1.6. Client-controlled Behavior . . . . . . . . . . . . . 89
13.2. Expiration Model . . . . . . . . . . . . . . . . . . . . 88 13.2. Expiration Model . . . . . . . . . . . . . . . . . . . . 90
13.2.1. Server-Specified Expiration . . . . . . . . . . . . 88 13.2.1. Server-Specified Expiration . . . . . . . . . . . . 90
13.2.2. Heuristic Expiration . . . . . . . . . . . . . . . . 88 13.2.2. Heuristic Expiration . . . . . . . . . . . . . . . . 90
13.2.3. Age Calculations . . . . . . . . . . . . . . . . . . 89 13.2.3. Age Calculations . . . . . . . . . . . . . . . . . . 91
13.2.4. Expiration Calculations . . . . . . . . . . . . . . 91 13.2.4. Expiration Calculations . . . . . . . . . . . . . . 93
13.2.5. Disambiguating Expiration Values . . . . . . . . . . 92 13.2.5. Disambiguating Expiration Values . . . . . . . . . . 94
13.2.6. Disambiguating Multiple Responses . . . . . . . . . 93 13.2.6. Disambiguating Multiple Responses . . . . . . . . . 95
13.3. Validation Model . . . . . . . . . . . . . . . . . . . . 93 13.3. Validation Model . . . . . . . . . . . . . . . . . . . . 95
13.3.1. Last-Modified Dates . . . . . . . . . . . . . . . . 94 13.3.1. Last-Modified Dates . . . . . . . . . . . . . . . . 96
13.3.2. Entity Tag Cache Validators . . . . . . . . . . . . 94 13.3.2. Entity Tag Cache Validators . . . . . . . . . . . . 96
13.3.3. Weak and Strong Validators . . . . . . . . . . . . . 95 13.3.3. Weak and Strong Validators . . . . . . . . . . . . . 97
13.3.4. Rules for When to Use Entity Tags and 13.3.4. Rules for When to Use Entity Tags and
Last-Modified Dates . . . . . . . . . . . . . . . . 97 Last-Modified Dates . . . . . . . . . . . . . . . . 99
13.3.5. Non-validating Conditionals . . . . . . . . . . . . 99 13.3.5. Non-validating Conditionals . . . . . . . . . . . . 101
13.4. Response Cacheability . . . . . . . . . . . . . . . . . 99 13.4. Response Cacheability . . . . . . . . . . . . . . . . . 101
13.5. Constructing Responses From Caches . . . . . . . . . . . 100 13.5. Constructing Responses From Caches . . . . . . . . . . . 102
13.5.1. End-to-end and Hop-by-hop Headers . . . . . . . . . 100 13.5.1. End-to-end and Hop-by-hop Headers . . . . . . . . . 102
13.5.2. Non-modifiable Headers . . . . . . . . . . . . . . . 101 13.5.2. Non-modifiable Headers . . . . . . . . . . . . . . . 103
13.5.3. Combining Headers . . . . . . . . . . . . . . . . . 102 13.5.3. Combining Headers . . . . . . . . . . . . . . . . . 104
13.5.4. Combining Byte Ranges . . . . . . . . . . . . . . . 103 13.5.4. Combining Byte Ranges . . . . . . . . . . . . . . . 105
13.6. Caching Negotiated Responses . . . . . . . . . . . . . . 104 13.6. Caching Negotiated Responses . . . . . . . . . . . . . . 106
13.7. Shared and Non-Shared Caches . . . . . . . . . . . . . . 105 13.7. Shared and Non-Shared Caches . . . . . . . . . . . . . . 107
13.8. Errors or Incomplete Response Cache Behavior . . . . . . 105 13.8. Errors or Incomplete Response Cache Behavior . . . . . . 107
13.9. Side Effects of GET and HEAD . . . . . . . . . . . . . . 106 13.9. Side Effects of GET and HEAD . . . . . . . . . . . . . . 108
13.10. Invalidation After Updates or Deletions . . . . . . . . 106 13.10. Invalidation After Updates or Deletions . . . . . . . . 108
13.11. Write-Through Mandatory . . . . . . . . . . . . . . . . 107 13.11. Write-Through Mandatory . . . . . . . . . . . . . . . . 109
13.12. Cache Replacement . . . . . . . . . . . . . . . . . . . 107 13.12. Cache Replacement . . . . . . . . . . . . . . . . . . . 109
13.13. History Lists . . . . . . . . . . . . . . . . . . . . . 108 13.13. History Lists . . . . . . . . . . . . . . . . . . . . . 110
14. Header Field Definitions . . . . . . . . . . . . . . . . . . 109 14. Header Field Definitions . . . . . . . . . . . . . . . . . . 111
14.1. Accept . . . . . . . . . . . . . . . . . . . . . . . . . 109 14.1. Accept . . . . . . . . . . . . . . . . . . . . . . . . . 111
14.2. Accept-Charset . . . . . . . . . . . . . . . . . . . . . 111 14.2. Accept-Charset . . . . . . . . . . . . . . . . . . . . . 113
14.3. Accept-Encoding . . . . . . . . . . . . . . . . . . . . 111 14.3. Accept-Encoding . . . . . . . . . . . . . . . . . . . . 113
14.4. Accept-Language . . . . . . . . . . . . . . . . . . . . 113 14.4. Accept-Language . . . . . . . . . . . . . . . . . . . . 115
14.5. Accept-Ranges . . . . . . . . . . . . . . . . . . . . . 114 14.5. Accept-Ranges . . . . . . . . . . . . . . . . . . . . . 116
14.6. Age . . . . . . . . . . . . . . . . . . . . . . . . . . 114 14.6. Age . . . . . . . . . . . . . . . . . . . . . . . . . . 116
14.7. Allow . . . . . . . . . . . . . . . . . . . . . . . . . 115 14.7. Allow . . . . . . . . . . . . . . . . . . . . . . . . . 117
14.8. Authorization . . . . . . . . . . . . . . . . . . . . . 116 14.8. Authorization . . . . . . . . . . . . . . . . . . . . . 118
14.9. Cache-Control . . . . . . . . . . . . . . . . . . . . . 116 14.9. Cache-Control . . . . . . . . . . . . . . . . . . . . . 118
14.9.1. What is Cacheable . . . . . . . . . . . . . . . . . 118 14.9.1. What is Cacheable . . . . . . . . . . . . . . . . . 120
14.9.2. What May be Stored by Caches . . . . . . . . . . . . 119 14.9.2. What May be Stored by Caches . . . . . . . . . . . . 121
14.9.3. Modifications of the Basic Expiration Mechanism . . 120 14.9.3. Modifications of the Basic Expiration Mechanism . . 122
14.9.4. Cache Revalidation and Reload Controls . . . . . . . 122 14.9.4. Cache Revalidation and Reload Controls . . . . . . . 124
14.9.5. No-Transform Directive . . . . . . . . . . . . . . . 125 14.9.5. No-Transform Directive . . . . . . . . . . . . . . . 127
14.9.6. Cache Control Extensions . . . . . . . . . . . . . . 125 14.9.6. Cache Control Extensions . . . . . . . . . . . . . . 127
14.10. Connection . . . . . . . . . . . . . . . . . . . . . . . 126 14.10. Connection . . . . . . . . . . . . . . . . . . . . . . . 128
14.11. Content-Encoding . . . . . . . . . . . . . . . . . . . . 127 14.11. Content-Encoding . . . . . . . . . . . . . . . . . . . . 129
14.12. Content-Language . . . . . . . . . . . . . . . . . . . . 128 14.12. Content-Language . . . . . . . . . . . . . . . . . . . . 130
14.13. Content-Length . . . . . . . . . . . . . . . . . . . . . 128 14.13. Content-Length . . . . . . . . . . . . . . . . . . . . . 130
14.14. Content-Location . . . . . . . . . . . . . . . . . . . . 129 14.14. Content-Location . . . . . . . . . . . . . . . . . . . . 131
14.15. Content-MD5 . . . . . . . . . . . . . . . . . . . . . . 130 14.15. Content-MD5 . . . . . . . . . . . . . . . . . . . . . . 132
14.16. Content-Range . . . . . . . . . . . . . . . . . . . . . 131 14.16. Content-Range . . . . . . . . . . . . . . . . . . . . . 133
14.17. Content-Type . . . . . . . . . . . . . . . . . . . . . . 133 14.17. Content-Type . . . . . . . . . . . . . . . . . . . . . . 135
14.18. Date . . . . . . . . . . . . . . . . . . . . . . . . . . 133 14.18. Date . . . . . . . . . . . . . . . . . . . . . . . . . . 136
14.18.1. Clockless Origin Server Operation . . . . . . . . . 134 14.18.1. Clockless Origin Server Operation . . . . . . . . . 137
14.19. ETag . . . . . . . . . . . . . . . . . . . . . . . . . . 135 14.19. ETag . . . . . . . . . . . . . . . . . . . . . . . . . . 137
14.20. Expect . . . . . . . . . . . . . . . . . . . . . . . . . 135 14.20. Expect . . . . . . . . . . . . . . . . . . . . . . . . . 137
14.21. Expires . . . . . . . . . . . . . . . . . . . . . . . . 136 14.21. Expires . . . . . . . . . . . . . . . . . . . . . . . . 138
14.22. From . . . . . . . . . . . . . . . . . . . . . . . . . . 137 14.22. From . . . . . . . . . . . . . . . . . . . . . . . . . . 139
14.23. Host . . . . . . . . . . . . . . . . . . . . . . . . . . 137 14.23. Host . . . . . . . . . . . . . . . . . . . . . . . . . . 140
14.24. If-Match . . . . . . . . . . . . . . . . . . . . . . . . 138 14.24. If-Match . . . . . . . . . . . . . . . . . . . . . . . . 140
14.25. If-Modified-Since . . . . . . . . . . . . . . . . . . . 139 14.25. If-Modified-Since . . . . . . . . . . . . . . . . . . . 141
14.26. If-None-Match . . . . . . . . . . . . . . . . . . . . . 141 14.26. If-None-Match . . . . . . . . . . . . . . . . . . . . . 143
14.27. If-Range . . . . . . . . . . . . . . . . . . . . . . . . 142 14.27. If-Range . . . . . . . . . . . . . . . . . . . . . . . . 144
14.28. If-Unmodified-Since . . . . . . . . . . . . . . . . . . 143 14.28. If-Unmodified-Since . . . . . . . . . . . . . . . . . . 145
14.29. Last-Modified . . . . . . . . . . . . . . . . . . . . . 143 14.29. Last-Modified . . . . . . . . . . . . . . . . . . . . . 145
14.30. Location . . . . . . . . . . . . . . . . . . . . . . . . 144 14.30. Location . . . . . . . . . . . . . . . . . . . . . . . . 146
14.31. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . 144 14.31. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . 147
14.32. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . 145 14.32. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . 147
14.33. Proxy-Authenticate . . . . . . . . . . . . . . . . . . . 146 14.33. Proxy-Authenticate . . . . . . . . . . . . . . . . . . . 148
14.34. Proxy-Authorization . . . . . . . . . . . . . . . . . . 146 14.34. Proxy-Authorization . . . . . . . . . . . . . . . . . . 149
14.35. Range . . . . . . . . . . . . . . . . . . . . . . . . . 147 14.35. Range . . . . . . . . . . . . . . . . . . . . . . . . . 149
14.35.1. Byte Ranges . . . . . . . . . . . . . . . . . . . . 147 14.35.1. Byte Ranges . . . . . . . . . . . . . . . . . . . . 149
14.35.2. Range Retrieval Requests . . . . . . . . . . . . . . 148 14.35.2. Range Retrieval Requests . . . . . . . . . . . . . . 151
14.36. Referer . . . . . . . . . . . . . . . . . . . . . . . . 149 14.36. Referer . . . . . . . . . . . . . . . . . . . . . . . . 152
14.37. Retry-After . . . . . . . . . . . . . . . . . . . . . . 150 14.37. Retry-After . . . . . . . . . . . . . . . . . . . . . . 152
14.38. Server . . . . . . . . . . . . . . . . . . . . . . . . . 150 14.38. Server . . . . . . . . . . . . . . . . . . . . . . . . . 152
14.39. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 14.39. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
14.40. Trailer . . . . . . . . . . . . . . . . . . . . . . . . 152 14.40. Trailer . . . . . . . . . . . . . . . . . . . . . . . . 154
14.41. Transfer-Encoding . . . . . . . . . . . . . . . . . . . 152 14.41. Transfer-Encoding . . . . . . . . . . . . . . . . . . . 155
14.42. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . 153 14.42. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . 155
14.43. User-Agent . . . . . . . . . . . . . . . . . . . . . . . 154 14.43. User-Agent . . . . . . . . . . . . . . . . . . . . . . . 156
14.44. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . 154 14.44. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . 157
14.45. Via . . . . . . . . . . . . . . . . . . . . . . . . . . 155 14.45. Via . . . . . . . . . . . . . . . . . . . . . . . . . . 157
14.46. Warning . . . . . . . . . . . . . . . . . . . . . . . . 157 14.46. Warning . . . . . . . . . . . . . . . . . . . . . . . . 159
14.47. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . 159 14.47. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . 162
15. Security Considerations . . . . . . . . . . . . . . . . . . . 160 15. Security Considerations . . . . . . . . . . . . . . . . . . . 163
15.1. Personal Information . . . . . . . . . . . . . . . . . . 160 15.1. Personal Information . . . . . . . . . . . . . . . . . . 163
15.1.1. Abuse of Server Log Information . . . . . . . . . . 160 15.1.1. Abuse of Server Log Information . . . . . . . . . . 163
15.1.2. Transfer of Sensitive Information . . . . . . . . . 160 15.1.2. Transfer of Sensitive Information . . . . . . . . . 163
15.1.3. Encoding Sensitive Information in URI's . . . . . . 161 15.1.3. Encoding Sensitive Information in URI's . . . . . . 164
15.1.4. Privacy Issues Connected to Accept Headers . . . . . 162 15.1.4. Privacy Issues Connected to Accept Headers . . . . . 165
15.2. Attacks Based On File and Path Names . . . . . . . . . . 162 15.2. Attacks Based On File and Path Names . . . . . . . . . . 165
15.3. DNS Spoofing . . . . . . . . . . . . . . . . . . . . . . 163 15.3. DNS Spoofing . . . . . . . . . . . . . . . . . . . . . . 166
15.4. Location Headers and Spoofing . . . . . . . . . . . . . 163 15.4. Location Headers and Spoofing . . . . . . . . . . . . . 166
15.5. Content-Disposition Issues . . . . . . . . . . . . . . . 164 15.5. Content-Disposition Issues . . . . . . . . . . . . . . . 167
15.6. Authentication Credentials and Idle Clients . . . . . . 164 15.6. Authentication Credentials and Idle Clients . . . . . . 167
15.7. Proxies and Caching . . . . . . . . . . . . . . . . . . 164 15.7. Proxies and Caching . . . . . . . . . . . . . . . . . . 167
15.7.1. Denial of Service Attacks on Proxies . . . . . . . . 165 15.7.1. Denial of Service Attacks on Proxies . . . . . . . . 168
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 166 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 169
16.1. (RFC2616) . . . . . . . . . . . . . . . . . . . . . . . 166 16.1. (RFC2616) . . . . . . . . . . . . . . . . . . . . . . . 169
16.2. (This Document) . . . . . . . . . . . . . . . . . . . . 168 16.2. (This Document) . . . . . . . . . . . . . . . . . . . . 170
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 169 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 171
17.1. References . . . . . . . . . . . . . . . . . . . . . . . 169 17.1. References . . . . . . . . . . . . . . . . . . . . . . . 171
17.2. Normative References . . . . . . . . . . . . . . . . . . 172 17.2. Informative References . . . . . . . . . . . . . . . . . 174
Appendix A. Internet Media Type message/http and Appendix A. Internet Media Type message/http and
application/http . . . . . . . . . . . . . . . . . . 174 application/http . . . . . . . . . . . . . . . . . . 176
Appendix B. Internet Media Type multipart/byteranges . . . . . . 176 Appendix B. Internet Media Type multipart/byteranges . . . . . . 178
Appendix C. Tolerant Applications . . . . . . . . . . . . . . . 178 Appendix C. Tolerant Applications . . . . . . . . . . . . . . . 180
Appendix D. Differences Between HTTP Entities and RFC 2045 Appendix D. Differences Between HTTP Entities and RFC 2045
Entities . . . . . . . . . . . . . . . . . . . . . . 179 Entities . . . . . . . . . . . . . . . . . . . . . . 181
D.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 179 D.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 181
D.2. Conversion to Canonical Form . . . . . . . . . . . . . . 179 D.2. Conversion to Canonical Form . . . . . . . . . . . . . . 181
D.3. Conversion of Date Formats . . . . . . . . . . . . . . . 180 D.3. Conversion of Date Formats . . . . . . . . . . . . . . . 182
D.4. Introduction of Content-Encoding . . . . . . . . . . . . 180 D.4. Introduction of Content-Encoding . . . . . . . . . . . . 182
D.5. No Content-Transfer-Encoding . . . . . . . . . . . . . . 180 D.5. No Content-Transfer-Encoding . . . . . . . . . . . . . . 182
D.6. Introduction of Transfer-Encoding . . . . . . . . . . . 181 D.6. Introduction of Transfer-Encoding . . . . . . . . . . . 183
D.7. MHTML and Line Length Limitations . . . . . . . . . . . 181 D.7. MHTML and Line Length Limitations . . . . . . . . . . . 183
Appendix E. Additional Features . . . . . . . . . . . . . . . . 182 Appendix E. Additional Features . . . . . . . . . . . . . . . . 184
E.1. Content-Disposition . . . . . . . . . . . . . . . . . . 182 E.1. Content-Disposition . . . . . . . . . . . . . . . . . . 184
Appendix F. Compatibility with Previous Versions . . . . . . . . 183 Appendix F. Compatibility with Previous Versions . . . . . . . . 185
F.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . 183 F.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . 185
F.1.1. Changes to Simplify Multi-homed Web Servers and F.1.1. Changes to Simplify Multi-homed Web Servers and
Conserve IP Addresses . . . . . . . . . . . . . . . 183 Conserve IP Addresses . . . . . . . . . . . . . . . 185
F.2. Compatibility with HTTP/1.0 Persistent Connections . . . 184 F.2. Compatibility with HTTP/1.0 Persistent Connections . . . 186
F.3. Changes from RFC 2068 . . . . . . . . . . . . . . . . . 185 F.3. Changes from RFC 2068 . . . . . . . . . . . . . . . . . 187
F.4. Changes from RFC 2616 . . . . . . . . . . . . . . . . . 189
Appendix G. Change Log (to be removed by RFC Editor before Appendix G. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 188 publication) . . . . . . . . . . . . . . . . . . . . 191
G.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . 188 G.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . 191
Appendix H. Open issues (to be removed by RFC Editor prior to G.2. Since draft-lafon-rfc2616bis-00 . . . . . . . . . . . . 191
publication) . . . . . . . . . . . . . . . . . . . . 189 Appendix H. Resolved issues (to be removed by RFC Editor
H.1. rfc2616bis . . . . . . . . . . . . . . . . . . . . . . . 189 before publication) . . . . . . . . . . . . . . . . 192
H.2. edit . . . . . . . . . . . . . . . . . . . . . . . . . . 189 H.1. rfc2606-compliance . . . . . . . . . . . . . . . . . . . 192
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 H.2. editor-notes . . . . . . . . . . . . . . . . . . . . . . 192
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 201 H.3. verscase . . . . . . . . . . . . . . . . . . . . . . . . 192
Intellectual Property and Copyright Statements . . . . . . . . . 202 H.4. unsafe-uri . . . . . . . . . . . . . . . . . . . . . . . 192
H.5. charactersets . . . . . . . . . . . . . . . . . . . . . 193
H.6. identity . . . . . . . . . . . . . . . . . . . . . . . . 193
H.7. chunk-size . . . . . . . . . . . . . . . . . . . . . . . 193
H.8. msg-len-chars . . . . . . . . . . . . . . . . . . . . . 194
H.9. uriquery . . . . . . . . . . . . . . . . . . . . . . . . 194
H.10. post . . . . . . . . . . . . . . . . . . . . . . . . . . 194
H.11. ifrange206 . . . . . . . . . . . . . . . . . . . . . . . 194
H.12. saferedirect . . . . . . . . . . . . . . . . . . . . . . 195
H.13. trailer-hop . . . . . . . . . . . . . . . . . . . . . . 195
H.14. invalidupd . . . . . . . . . . . . . . . . . . . . . . . 195
H.15. noclose1xx . . . . . . . . . . . . . . . . . . . . . . . 196
H.16. via-must . . . . . . . . . . . . . . . . . . . . . . . . 196
Appendix I. Open issues (to be removed by RFC Editor prior to
publication) . . . . . . . . . . . . . . . . . . . . 197
I.1. rfc2616bis . . . . . . . . . . . . . . . . . . . . . . . 197
I.2. unneeded_references . . . . . . . . . . . . . . . . . . 197
I.3. edit . . . . . . . . . . . . . . . . . . . . . . . . . . 197
I.4. media-reg . . . . . . . . . . . . . . . . . . . . . . . 197
I.5. languagetag . . . . . . . . . . . . . . . . . . . . . . 197
I.6. location-fragments . . . . . . . . . . . . . . . . . . . 198
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 210
Intellectual Property and Copyright Statements . . . . . . . . . 213
1. Introduction 1. Introduction
1.1. Purpose 1.1. Purpose
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information protocol for distributed, collaborative, hypermedia information
systems. HTTP has been in use by the World-Wide Web global systems. HTTP has been in use by the World-Wide Web global
information initiative since 1990. The first version of HTTP, information initiative since 1990. The first version of HTTP,
referred to as HTTP/0.9, was a simple protocol for raw data transfer referred to as HTTP/0.9, was a simple protocol for raw data transfer
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The mechanism for selecting the appropriate representation when The mechanism for selecting the appropriate representation when
servicing a request, as described in Section 12. The servicing a request, as described in Section 12. The
representation of entities in any response can be negotiated representation of entities in any response can be negotiated
(including error responses). (including error responses).
variant variant
A resource may have one, or more than one, representation(s) A resource may have one, or more than one, representation(s)
associated with it at any given instant. Each of these associated with it at any given instant. Each of these
representations is termed a `varriant'. Use of the term `variant' representations is termed a `variant'. Use of the term `variant'
does not necessarily imply that the resource is subject to content does not necessarily imply that the resource is subject to content
negotiation. negotiation.
client client
A program that establishes connections for the purpose of sending A program that establishes connections for the purpose of sending
requests. requests.
user agent user agent
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including the message's protocol version and a success or error code, including the message's protocol version and a success or error code,
followed by a MIME-like message containing server information, entity followed by a MIME-like message containing server information, entity
metainformation, and possible entity-body content. The relationship metainformation, and possible entity-body content. The relationship
between HTTP and MIME is described in Appendix D. between HTTP and MIME is described in Appendix D.
Most HTTP communication is initiated by a user agent and consists of Most HTTP communication is initiated by a user agent and consists of
a request to be applied to a resource on some origin server. In the a request to be applied to a resource on some origin server. In the
simplest case, this may be accomplished via a single connection (v) simplest case, this may be accomplished via a single connection (v)
between the user agent (UA) and the origin server (O). between the user agent (UA) and the origin server (O).
request chain ------------------------> request chain ------------------------>
UA -------------------v------------------- O UA -------------------v------------------- O
<----------------------- response chain <----------------------- response chain
A more complicated situation occurs when one or more intermediaries A more complicated situation occurs when one or more intermediaries
are present in the request/response chain. There are three common are present in the request/response chain. There are three common
forms of intermediary: proxy, gateway, and tunnel. A proxy is a forms of intermediary: proxy, gateway, and tunnel. A proxy is a
forwarding agent, receiving requests for a URI in its absolute form, forwarding agent, receiving requests for a URI in its absolute form,
rewriting all or part of the message, and forwarding the reformatted rewriting all or part of the message, and forwarding the reformatted
request toward the server identified by the URI. A gateway is a request toward the server identified by the URI. A gateway is a
receiving agent, acting as a layer above some other server(s) and, if receiving agent, acting as a layer above some other server(s) and, if
necessary, translating the requests to the underlying server's necessary, translating the requests to the underlying server's
protocol. A tunnel acts as a relay point between two connections protocol. A tunnel acts as a relay point between two connections
without changing the messages; tunnels are used when the without changing the messages; tunnels are used when the
communication needs to pass through an intermediary (such as a communication needs to pass through an intermediary (such as a
firewall) even when the intermediary cannot understand the contents firewall) even when the intermediary cannot understand the contents
of the messages. of the messages.
request chain --------------------------------------> request chain -------------------------------------->
UA -----v----- A -----v----- B -----v----- C -----v----- O UA -----v----- A -----v----- B -----v----- C -----v----- O
<------------------------------------- response chain <------------------------------------- response chain
The figure above shows three intermediaries (A, B, and C) between the The figure above shows three intermediaries (A, B, and C) between the
user agent and origin server. A request or response message that user agent and origin server. A request or response message that
travels the whole chain will pass through four separate connections. travels the whole chain will pass through four separate connections.
This distinction is important because some HTTP communication options This distinction is important because some HTTP communication options
may apply only to the connection with the nearest, non-tunnel may apply only to the connection with the nearest, non-tunnel
neighbor, only to the end-points of the chain, or to all connections neighbor, only to the end-points of the chain, or to all connections
along the chain. Although the diagram is linear, each participant along the chain. Although the diagram is linear, each participant
may be engaged in multiple, simultaneous communications. For may be engaged in multiple, simultaneous communications. For
example, B may be receiving requests from many clients other than A, example, B may be receiving requests from many clients other than A,
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separators) MUST exist between any two tokens (for the definition separators) MUST exist between any two tokens (for the definition
of "token" below), since they would otherwise be interpreted as a of "token" below), since they would otherwise be interpreted as a
single token. single token.
2.2. Basic Rules 2.2. Basic Rules
The following rules are used throughout this specification to The following rules are used throughout this specification to
describe basic parsing constructs. The US-ASCII coded character set describe basic parsing constructs. The US-ASCII coded character set
is defined by ANSI X3.4-1986 [21]. is defined by ANSI X3.4-1986 [21].
OCTET = <any 8-bit sequence of data> OCTET = <any 8-bit sequence of data>
CHAR = <any US-ASCII character (octets 0 - 127)> CHAR = <any US-ASCII character (octets 0 - 127)>
UPALPHA = <any US-ASCII uppercase letter "A".."Z"> UPALPHA = <any US-ASCII uppercase letter "A".."Z">
LOALPHA = <any US-ASCII lowercase letter "a".."z"> LOALPHA = <any US-ASCII lowercase letter "a".."z">
ALPHA = UPALPHA | LOALPHA ALPHA = UPALPHA | LOALPHA
DIGIT = <any US-ASCII digit "0".."9"> DIGIT = <any US-ASCII digit "0".."9">
CTL = <any US-ASCII control character CTL = <any US-ASCII control character
(octets 0 - 31) and DEL (127)> (octets 0 - 31) and DEL (127)>
CR = <US-ASCII CR, carriage return (13)> CR = <US-ASCII CR, carriage return (13)>
LF = <US-ASCII LF, linefeed (10)> LF = <US-ASCII LF, linefeed (10)>
SP = <US-ASCII SP, space (32)> SP = <US-ASCII SP, space (32)>
HT = <US-ASCII HT, horizontal-tab (9)> HT = <US-ASCII HT, horizontal-tab (9)>
<"> = <US-ASCII double-quote mark (34)> <"> = <US-ASCII double-quote mark (34)>
HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all
protocol elements except the entity-body (see Appendix C for tolerant protocol elements except the entity-body (see Appendix C for tolerant
applications). The end-of-line marker within an entity-body is applications). The end-of-line marker within an entity-body is
defined by its associated media type, as described in Section 3.7. defined by its associated media type, as described in Section 3.7.
CRLF = CR LF CRLF = CR LF
HTTP/1.1 header field values can be folded onto multiple lines if the HTTP/1.1 header field values can be folded onto multiple lines if the
continuation line begins with a space or horizontal tab. All linear continuation line begins with a space or horizontal tab. All linear
white space, including folding, has the same semantics as SP. A white space, including folding, has the same semantics as SP. A
recipient MAY replace any linear white space with a single SP before recipient MAY replace any linear white space with a single SP before
interpreting the field value or forwarding the message downstream. interpreting the field value or forwarding the message downstream.
LWS = [CRLF] 1*( SP | HT ) LWS = [CRLF] 1*( SP | HT )
The TEXT rule is only used for descriptive field contents and values The TEXT rule is only used for descriptive field contents and values
that are not intended to be interpreted by the message parser. Words that are not intended to be interpreted by the message parser. Words
of *TEXT MAY contain characters from character sets other than ISO- of *TEXT MAY contain characters from character sets other than ISO-
8859-1 [22] only when encoded according to the rules of RFC 2047 8859-1 [22] only when encoded according to the rules of RFC 2047
[14]. [14].
TEXT = <any OCTET except CTLs, TEXT = <any OCTET except CTLs,
but including LWS> but including LWS>
A CRLF is allowed in the definition of TEXT only as part of a header A CRLF is allowed in the definition of TEXT only as part of a header
field continuation. It is expected that the folding LWS will be field continuation. It is expected that the folding LWS will be
replaced with a single SP before interpretation of the TEXT value. replaced with a single SP before interpretation of the TEXT value.
Hexadecimal numeric characters are used in several protocol elements. Hexadecimal numeric characters are used in several protocol elements.
HEX = "A" | "B" | "C" | "D" | "E" | "F" HEX = "A" | "B" | "C" | "D" | "E" | "F"
| "a" | "b" | "c" | "d" | "e" | "f" | DIGIT | "a" | "b" | "c" | "d" | "e" | "f" | DIGIT
Many HTTP/1.1 header field values consist of words separated by LWS Many HTTP/1.1 header field values consist of words separated by LWS
or special characters. These special characters MUST be in a quoted or special characters. These special characters MUST be in a quoted
string to be used within a parameter value (as defined in string to be used within a parameter value (as defined in
Section 3.6). Section 3.6).
token = 1*<any CHAR except CTLs or separators> token = 1*<any CHAR except CTLs or separators>
separators = "(" | ")" | "<" | ">" | "@" separators = "(" | ")" | "<" | ">" | "@"
| "," | ";" | ":" | "\" | <"> | "," | ";" | ":" | "\" | <">
| "/" | "[" | "]" | "?" | "=" | "/" | "[" | "]" | "?" | "="
| "{" | "}" | SP | HT | "{" | "}" | SP | HT
Comments can be included in some HTTP header fields by surrounding Comments can be included in some HTTP header fields by surrounding
the comment text with parentheses. Comments are only allowed in the comment text with parentheses. Comments are only allowed in
fields containing "comment" as part of their field value definition. fields containing "comment" as part of their field value definition.
In all other fields, parentheses are considered part of the field In all other fields, parentheses are considered part of the field
value. value.
comment = "(" *( ctext | quoted-pair | comment ) ")" comment = "(" *( ctext | quoted-pair | comment ) ")"
ctext = <any TEXT excluding "(" and ")"> ctext = <any TEXT excluding "(" and ")">
A string of text is parsed as a single word if it is quoted using A string of text is parsed as a single word if it is quoted using
double-quote marks. double-quote marks.
quoted-string = ( <"> *(qdtext | quoted-pair ) <"> ) quoted-string = ( <"> *(qdtext | quoted-pair ) <"> )
qdtext = <any TEXT except <">> qdtext = <any TEXT except <">>
The backslash character ("\") MAY be used as a single-character The backslash character ("\") MAY be used as a single-character
quoting mechanism only within quoted-string and comment constructs. quoting mechanism only within quoted-string and comment constructs.
quoted-pair = "\" CHAR quoted-pair = "\" CHAR
3. Protocol Parameters 3. Protocol Parameters
3.1. HTTP Version 3.1. HTTP Version
HTTP uses a "<major>.<minor>" numbering scheme to indicate versions HTTP uses a "<major>.<minor>" numbering scheme to indicate versions
of the protocol. The protocol versioning policy is intended to allow of the protocol. The protocol versioning policy is intended to allow
the sender to indicate the format of a message and its capacity for the sender to indicate the format of a message and its capacity for
understanding further HTTP communication, rather than the features understanding further HTTP communication, rather than the features
obtained via that communication. No change is made to the version obtained via that communication. No change is made to the version
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An application that sends a request or response message that includes An application that sends a request or response message that includes
HTTP-Version of "HTTP/1.1" MUST be at least conditionally compliant HTTP-Version of "HTTP/1.1" MUST be at least conditionally compliant
with this specification. Applications that are at least with this specification. Applications that are at least
conditionally compliant with this specification SHOULD use an HTTP- conditionally compliant with this specification SHOULD use an HTTP-
Version of "HTTP/1.1" in their messages, and MUST do so for any Version of "HTTP/1.1" in their messages, and MUST do so for any
message that is not compatible with HTTP/1.0. For more details on message that is not compatible with HTTP/1.0. For more details on
when to send specific HTTP-Version values, see RFC 2145 [36]. when to send specific HTTP-Version values, see RFC 2145 [36].
The HTTP version of an application is the highest HTTP version for The HTTP version of an application is the highest HTTP version for
which the application is at least conditionally compliant. which the application is at least conditionally compliant. HTTP-
Version is case-sensitive.
Proxy and gateway applications need to be careful when forwarding Proxy and gateway applications need to be careful when forwarding
messages in protocol versions different from that of the application. messages in protocol versions different from that of the application.
Since the protocol version indicates the protocol capability of the Since the protocol version indicates the protocol capability of the
sender, a proxy/gateway MUST NOT send a message with a version sender, a proxy/gateway MUST NOT send a message with a version
indicator which is greater than its actual version. If a higher indicator which is greater than its actual version. If a higher
version request is received, the proxy/gateway MUST either downgrade version request is received, the proxy/gateway MUST either downgrade
the request version, or respond with an error, or switch to tunnel the request version, or respond with an error, or switch to tunnel
behavior. behavior.
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Note: Servers ought to be cautious about depending on URI lengths Note: Servers ought to be cautious about depending on URI lengths
above 255 bytes, because some older client or proxy above 255 bytes, because some older client or proxy
implementations might not properly support these lengths. implementations might not properly support these lengths.
3.2.2. http URL 3.2.2. http URL
The "http" scheme is used to locate network resources via the HTTP The "http" scheme is used to locate network resources via the HTTP
protocol. This section defines the scheme-specific syntax and protocol. This section defines the scheme-specific syntax and
semantics for http URLs. semantics for http URLs.
http_URL = "http:" "//" host [ ":" port ] [ abs_path [ "?" query ]] http_URL = "http:" "//" host [ ":" port ] [ abs_path [ "?" query ]]
If the port is empty or not given, port 80 is assumed. The semantics If the port is empty or not given, port 80 is assumed. The semantics
are that the identified resource is located at the server listening are that the identified resource is located at the server listening
for TCP connections on that port of that host, and the Request-URI for TCP connections on that port of that host, and the Request-URI
for the resource is abs_path (section 5.1.2). The use of IP for the resource is abs_path (Section 5.1.2). The use of IP
addresses in URLs SHOULD be avoided whenever possible (see RFC 1900 addresses in URLs SHOULD be avoided whenever possible (see RFC 1900
[24]). If the abs_path is not present in the URL, it MUST be given [24]). If the abs_path is not present in the URL, it MUST be given
as "/" when used as a Request-URI for a resource (section 5.1.2). If as "/" when used as a Request-URI for a resource (Section 5.1.2). If
a proxy receives a host name which is not a fully qualified domain a proxy receives a host name which is not a fully qualified domain
name, it MAY add its domain to the host name it received. If a proxy name, it MAY add its domain to the host name it received. If a proxy
receives a fully qualified domain name, the proxy MUST NOT change the receives a fully qualified domain name, the proxy MUST NOT change the
host name. host name.
3.2.3. URI Comparison 3.2.3. URI Comparison
When comparing two URIs to decide if they match or not, a client When comparing two URIs to decide if they match or not, a client
SHOULD use a case-sensitive octet-by-octet comparison of the entire SHOULD use a case-sensitive octet-by-octet comparison of the entire
URIs, with these exceptions: URIs, with these exceptions:
o A port that is empty or not given is equivalent to the default o A port that is empty or not given is equivalent to the default
port for that URI-reference; port for that URI-reference;
o Comparisons of host names MUST be case-insensitive; o Comparisons of host names MUST be case-insensitive;
o Comparisons of scheme names MUST be case-insensitive; o Comparisons of scheme names MUST be case-insensitive;
o An empty abs_path is equivalent to an abs_path of "/". o An empty abs_path is equivalent to an abs_path of "/".
Characters other than those in the "reserved" and "unsafe" sets (see Characters other than those in the "reserved" set (see RFC 2396 [42])
RFC 2396 [42]) are equivalent to their ""%" HEX HEX" encoding. are equivalent to their ""%" HEX HEX" encoding.
For example, the following three URIs are equivalent: For example, the following three URIs are equivalent:
http://abc.com:80/~smith/home.html http://abc.com:80/~smith/home.html
http://ABC.com/%7Esmith/home.html http://ABC.com/%7Esmith/home.html
http://ABC.com:/%7esmith/home.html http://ABC.com:/%7esmith/home.html
3.3. Date/Time Formats 3.3. Date/Time Formats
3.3.1. Full Date 3.3.1. Full Date
HTTP applications have historically allowed three different formats HTTP applications have historically allowed three different formats
for the representation of date/time stamps: for the representation of date/time stamps:
Sun, 06 Nov 1994 08:49:37 GMT ; RFC 822, updated by RFC 1123 Sun, 06 Nov 1994 08:49:37 GMT ; RFC 822, updated by RFC 1123
Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036 Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
Sun Nov 6 08:49:37 1994 ; ANSI C's asctime() format Sun Nov 6 08:49:37 1994 ; ANSI C's asctime() format
The first format is preferred as an Internet standard and represents The first format is preferred as an Internet standard and represents
a fixed-length subset of that defined by RFC 1123 [8] (an update to a fixed-length subset of that defined by RFC 1123 [8] (an update to
RFC 822 [9]). The second format is in common use, but is based on RFC 822 [9]). The second format is in common use, but is based on
the obsolete RFC 850 [12] date format and lacks a four-digit year. the obsolete RFC 850 [12] date format and lacks a four-digit year.
HTTP/1.1 clients and servers that parse the date value MUST accept HTTP/1.1 clients and servers that parse the date value MUST accept
all three formats (for compatibility with HTTP/1.0), though they MUST all three formats (for compatibility with HTTP/1.0), though they MUST
only generate the RFC 1123 format for representing HTTP-date values only generate the RFC 1123 format for representing HTTP-date values
in header fields. See Appendix C for further information. in header fields. See Appendix C for further information.
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All HTTP date/time stamps MUST be represented in Greenwich Mean Time All HTTP date/time stamps MUST be represented in Greenwich Mean Time
(GMT), without exception. For the purposes of HTTP, GMT is exactly (GMT), without exception. For the purposes of HTTP, GMT is exactly
equal to UTC (Coordinated Universal Time). This is indicated in the equal to UTC (Coordinated Universal Time). This is indicated in the
first two formats by the inclusion of "GMT" as the three-letter first two formats by the inclusion of "GMT" as the three-letter
abbreviation for time zone, and MUST be assumed when reading the abbreviation for time zone, and MUST be assumed when reading the
asctime format. HTTP-date is case sensitive and MUST NOT include asctime format. HTTP-date is case sensitive and MUST NOT include
additional LWS beyond that specifically included as SP in the additional LWS beyond that specifically included as SP in the
grammar. grammar.
HTTP-date = rfc1123-date | rfc850-date | asctime-date HTTP-date = rfc1123-date | rfc850-date | asctime-date
rfc1123-date = wkday "," SP date1 SP time SP "GMT" rfc1123-date = wkday "," SP date1 SP time SP "GMT"
rfc850-date = weekday "," SP date2 SP time SP "GMT" rfc850-date = weekday "," SP date2 SP time SP "GMT"
asctime-date = wkday SP date3 SP time SP 4DIGIT asctime-date = wkday SP date3 SP time SP 4DIGIT
date1 = 2DIGIT SP month SP 4DIGIT date1 = 2DIGIT SP month SP 4DIGIT
; day month year (e.g., 02 Jun 1982) ; day month year (e.g., 02 Jun 1982)
date2 = 2DIGIT "-" month "-" 2DIGIT date2 = 2DIGIT "-" month "-" 2DIGIT
; day-month-year (e.g., 02-Jun-82) ; day-month-year (e.g., 02-Jun-82)
date3 = month SP ( 2DIGIT | ( SP 1DIGIT )) date3 = month SP ( 2DIGIT | ( SP 1DIGIT ))
; month day (e.g., Jun 2) ; month day (e.g., Jun 2)
time = 2DIGIT ":" 2DIGIT ":" 2DIGIT time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
; 00:00:00 - 23:59:59 ; 00:00:00 - 23:59:59
wkday = "Mon" | "Tue" | "Wed" wkday = "Mon" | "Tue" | "Wed"
| "Thu" | "Fri" | "Sat" | "Sun" | "Thu" | "Fri" | "Sat" | "Sun"
weekday = "Monday" | "Tuesday" | "Wednesday" weekday = "Monday" | "Tuesday" | "Wednesday"
| "Thursday" | "Friday" | "Saturday" | "Sunday" | "Thursday" | "Friday" | "Saturday" | "Sunday"
month = "Jan" | "Feb" | "Mar" | "Apr" month = "Jan" | "Feb" | "Mar" | "Apr"
| "May" | "Jun" | "Jul" | "Aug" | "May" | "Jun" | "Jul" | "Aug"
| "Sep" | "Oct" | "Nov" | "Dec" | "Sep" | "Oct" | "Nov" | "Dec"
Note: HTTP requirements for the date/time stamp format apply only to Note: HTTP requirements for the date/time stamp format apply only to
their usage within the protocol stream. Clients and servers are not their usage within the protocol stream. Clients and servers are not
required to use these formats for user presentation, request logging, required to use these formats for user presentation, request logging,
etc. etc.
3.3.2. Delta Seconds 3.3.2. Delta Seconds
Some HTTP header fields allow a time value to be specified as an Some HTTP header fields allow a time value to be specified as an
integer number of seconds, represented in decimal, after the time integer number of seconds, represented in decimal, after the time
that the message was received. that the message was received.
delta-seconds = 1*DIGIT delta-seconds = 1*DIGIT
3.4. Character Sets 3.4. Character Sets
HTTP uses the same definition of the term "character set" as that HTTP uses the same definition of the term "character set" as that
described for MIME: described for MIME:
The term "character set" is used in this document to refer to a The term "character set" is used in this document to refer to a
method used with one or more tables to convert a sequence of octets method used with one or more tables to convert a sequence of octets
into a sequence of characters. Note that unconditional conversion in into a sequence of characters. Note that unconditional conversion in
the other direction is not required, in that not all characters may the other direction is not required, in that not all characters may
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Note: This use of the term "character set" is more commonly Note: This use of the term "character set" is more commonly
referred to as a "character encoding." However, since HTTP and referred to as a "character encoding." However, since HTTP and
MIME share the same registry, it is important that the terminology MIME share the same registry, it is important that the terminology
also be shared. also be shared.
HTTP character sets are identified by case-insensitive tokens. The HTTP character sets are identified by case-insensitive tokens. The
complete set of tokens is defined by the IANA Character Set registry complete set of tokens is defined by the IANA Character Set registry
[19]. [19].
charset = token charset = token
Although HTTP allows an arbitrary token to be used as a charset Although HTTP allows an arbitrary token to be used as a charset
value, any token that has a predefined value within the IANA value, any token that has a predefined value within the IANA
Character Set registry [19] MUST represent the character set defined Character Set registry [19] MUST represent the character set defined
by that registry. Applications SHOULD limit their use of character by that registry. Applications SHOULD limit their use of character
sets to those defined by the IANA registry. sets to those defined by the IANA registry.
HTTP uses charset in two contexts: within an Accept-Charset request
header (in which the charset value is an unquoted token) and as the
value of a parameter in a Content-Type header (within a request or
response), in which case the parameter value of the charset parameter
may be quoted.
Implementors should be aware of IETF character set requirements [38] Implementors should be aware of IETF character set requirements [38]
[41]. [41].
3.4.1. Missing Charset 3.4.1. Missing Charset
Some HTTP/1.0 software has interpreted a Content-Type header without Some HTTP/1.0 software has interpreted a Content-Type header without
charset parameter incorrectly to mean "recipient should guess." charset parameter incorrectly to mean "recipient should guess."
Senders wishing to defeat this behavior MAY include a charset Senders wishing to defeat this behavior MAY include a charset
parameter even when the charset is ISO-8859-1 and SHOULD do so when parameter even when the charset is ISO-8859-1 and SHOULD do so when
it is known that it will not confuse the recipient. it is known that it will not confuse the recipient.
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3.5. Content Codings 3.5. Content Codings
Content coding values indicate an encoding transformation that has Content coding values indicate an encoding transformation that has
been or can be applied to an entity. Content codings are primarily been or can be applied to an entity. Content codings are primarily
used to allow a document to be compressed or otherwise usefully used to allow a document to be compressed or otherwise usefully
transformed without losing the identity of its underlying media type transformed without losing the identity of its underlying media type
and without loss of information. Frequently, the entity is stored in and without loss of information. Frequently, the entity is stored in
coded form, transmitted directly, and only decoded by the recipient. coded form, transmitted directly, and only decoded by the recipient.
content-coding = token content-coding = token
All content-coding values are case-insensitive. HTTP/1.1 uses All content-coding values are case-insensitive. HTTP/1.1 uses
content-coding values in the Accept-Encoding (Section 14.3) and content-coding values in the Accept-Encoding (Section 14.3) and
Content-Encoding (Section 14.11) header fields. Although the value Content-Encoding (Section 14.11) header fields. Although the value
describes the content-coding, what is more important is that it describes the content-coding, what is more important is that it
indicates what decoding mechanism will be required to remove the indicates what decoding mechanism will be required to remove the
encoding. encoding.
The Internet Assigned Numbers Authority (IANA) acts as a registry for The Internet Assigned Numbers Authority (IANA) acts as a registry for
content-coding value tokens. Initially, the registry contains the content-coding value tokens. Initially, the registry contains the
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conform to the purpose of content coding defined in this section. conform to the purpose of content coding defined in this section.
3.6. Transfer Codings 3.6. Transfer Codings
Transfer-coding values are used to indicate an encoding Transfer-coding values are used to indicate an encoding
transformation that has been, can be, or may need to be applied to an transformation that has been, can be, or may need to be applied to an
entity-body in order to ensure "safe transport" through the network. entity-body in order to ensure "safe transport" through the network.
This differs from a content coding in that the transfer-coding is a This differs from a content coding in that the transfer-coding is a
property of the message, not of the original entity. property of the message, not of the original entity.
transfer-coding = "chunked" | transfer-extension transfer-coding = "chunked" | transfer-extension
transfer-extension = token *( ";" parameter ) transfer-extension = token *( ";" parameter )
Parameters are in the form of attribute/value pairs. Parameters are in the form of attribute/value pairs.
parameter = attribute "=" value parameter = attribute "=" value
attribute = token attribute = token
value = token | quoted-string value = token | quoted-string
All transfer-coding values are case-insensitive. HTTP/1.1 uses All transfer-coding values are case-insensitive. HTTP/1.1 uses
transfer-coding values in the TE header field (Section 14.39) and in transfer-coding values in the TE header field (Section 14.39) and in
the Transfer-Encoding header field (Section 14.41). the Transfer-Encoding header field (Section 14.41).
Whenever a transfer-coding is applied to a message-body, the set of Whenever a transfer-coding is applied to a message-body, the set of
transfer-codings MUST include "chunked", unless the message is transfer-codings MUST include "chunked", unless the message is
terminated by closing the connection. When the "chunked" transfer- terminated by closing the connection. When the "chunked" transfer-
coding is used, it MUST be the last transfer-coding applied to the coding is used, it MUST be the last transfer-coding applied to the
message-body. The "chunked" transfer-coding MUST NOT be applied more message-body. The "chunked" transfer-coding MUST NOT be applied more
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Transfer-codings are analogous to the Content-Transfer-Encoding Transfer-codings are analogous to the Content-Transfer-Encoding
values of MIME [7], which were designed to enable safe transport of values of MIME [7], which were designed to enable safe transport of
binary data over a 7-bit transport service. However, safe transport binary data over a 7-bit transport service. However, safe transport
has a different focus for an 8bit-clean transfer protocol. In HTTP, has a different focus for an 8bit-clean transfer protocol. In HTTP,
the only unsafe characteristic of message-bodies is the difficulty in the only unsafe characteristic of message-bodies is the difficulty in
determining the exact body length (Section 7.2.2), or the desire to determining the exact body length (Section 7.2.2), or the desire to
encrypt data over a shared transport. encrypt data over a shared transport.
The Internet Assigned Numbers Authority (IANA) acts as a registry for The Internet Assigned Numbers Authority (IANA) acts as a registry for
transfer-coding value tokens. Initially, the registry contains the transfer-coding value tokens. Initially, the registry contains the
following tokens: "chunked" (Section 3.6.1), "identity" (section following tokens: "chunked" (Section 3.6.1), "gzip" (Section 3.5),
3.6.2), "gzip" (Section 3.5), "compress" (Section 3.5), and "deflate" "compress" (Section 3.5), and "deflate" (Section 3.5).
(Section 3.5).
New transfer-coding value tokens SHOULD be registered in the same way New transfer-coding value tokens SHOULD be registered in the same way
as new content-coding value tokens (Section 3.5). as new content-coding value tokens (Section 3.5).
A server which receives an entity-body with a transfer-coding it does A server which receives an entity-body with a transfer-coding it does
not understand SHOULD return 501 (Unimplemented), and close the not understand SHOULD return 501 (Unimplemented), and close the
connection. A server MUST NOT send transfer-codings to an HTTP/1.0 connection. A server MUST NOT send transfer-codings to an HTTP/1.0
client. client.
3.6.1. Chunked Transfer Coding 3.6.1. Chunked Transfer Coding
The chunked encoding modifies the body of a message in order to The chunked encoding modifies the body of a message in order to
transfer it as a series of chunks, each with its own size indicator, transfer it as a series of chunks, each with its own size indicator,
followed by an OPTIONAL trailer containing entity-header fields. followed by an OPTIONAL trailer containing entity-header fields.
This allows dynamically produced content to be transferred along with This allows dynamically produced content to be transferred along with
the information necessary for the recipient to verify that it has the information necessary for the recipient to verify that it has
received the full message. received the full message.
Chunked-Body = *chunk Chunked-Body = *chunk
last-chunk last-chunk
trailer trailer
CRLF CRLF
chunk = chunk-size [ chunk-extension ] CRLF chunk = chunk-size [ chunk-extension ] CRLF
chunk-data CRLF chunk-data CRLF
chunk-size = 1*HEX chunk-size = 1*HEX
last-chunk = 1*("0") [ chunk-extension ] CRLF last-chunk = 1*("0") [ chunk-extension ] CRLF
chunk-extension= *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-extension= *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token | quoted-string chunk-ext-val = token | quoted-string
chunk-data = chunk-size(OCTET) chunk-data = chunk-size(OCTET)
trailer = *(entity-header CRLF) trailer = *(entity-header CRLF)
The chunk-size field is a string of hex digits indicating the size of The chunk-size field is a string of hex digits indicating the size of
the chunk. The chunked encoding is ended by any chunk whose size is the chunk-data in octets. The chunked encoding is ended by any chunk
zero, followed by the trailer, which is terminated by an empty line. whose size is zero, followed by the trailer, which is terminated by
an empty line.
The trailer allows the sender to include additional HTTP header The trailer allows the sender to include additional HTTP header
fields at the end of the message. The Trailer header field can be fields at the end of the message. The Trailer header field can be
used to indicate which header fields are included in a trailer (see used to indicate which header fields are included in a trailer (see
Section 14.40). Section 14.40).
A server using chunked transfer-coding in a response MUST NOT use the A server using chunked transfer-coding in a response MUST NOT use the
trailer for any header fields unless at least one of the following is trailer for any header fields unless at least one of the following is
true: true:
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All HTTP/1.1 applications MUST be able to receive and decode the All HTTP/1.1 applications MUST be able to receive and decode the
"chunked" transfer-coding, and MUST ignore chunk-extension extensions "chunked" transfer-coding, and MUST ignore chunk-extension extensions
they do not understand. they do not understand.
3.7. Media Types 3.7. Media Types
HTTP uses Internet Media Types [17] in the Content-Type HTTP uses Internet Media Types [17] in the Content-Type
(Section 14.17) and Accept (Section 14.1) header fields in order to (Section 14.17) and Accept (Section 14.1) header fields in order to
provide open and extensible data typing and type negotiation. provide open and extensible data typing and type negotiation.
media-type = type "/" subtype *( ";" parameter ) media-type = type "/" subtype *( ";" parameter )
type = token type = token
subtype = token subtype = token
Parameters MAY follow the type/subtype in the form of attribute/value Parameters MAY follow the type/subtype in the form of attribute/value
pairs (as defined in Section 3.6). pairs (as defined in Section 3.6).
The type, subtype, and parameter attribute names are case- The type, subtype, and parameter attribute names are case-
insensitive. Parameter values might or might not be case-sensitive, insensitive. Parameter values might or might not be case-sensitive,
depending on the semantics of the parameter name. Linear white space depending on the semantics of the parameter name. Linear white space
(LWS) MUST NOT be used between the type and subtype, nor between an (LWS) MUST NOT be used between the type and subtype, nor between an
attribute and its value. The presence or absence of a parameter attribute and its value. The presence or absence of a parameter
might be significant to the processing of a media-type, depending on might be significant to the processing of a media-type, depending on
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3.8. Product Tokens 3.8. Product Tokens
Product tokens are used to allow communicating applications to Product tokens are used to allow communicating applications to
identify themselves by software name and version. Most fields using identify themselves by software name and version. Most fields using
product tokens also allow sub-products which form a significant part product tokens also allow sub-products which form a significant part
of the application to be listed, separated by white space. By of the application to be listed, separated by white space. By
convention, the products are listed in order of their significance convention, the products are listed in order of their significance
for identifying the application. for identifying the application.
product = token ["/" product-version] product = token ["/" product-version]
product-version = token product-version = token
Examples: Examples:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3 User-Agent: CERN-LineMode/2.15 libwww/2.17b3
Server: Apache/0.8.4 Server: Apache/0.8.4
Product tokens SHOULD be short and to the point. They MUST NOT be Product tokens SHOULD be short and to the point. They MUST NOT be
used for advertising or other non-essential information. Although used for advertising or other non-essential information. Although
any token character MAY appear in a product-version, this token any token character MAY appear in a product-version, this token
SHOULD only be used for a version identifier (i.e., successive SHOULD only be used for a version identifier (i.e., successive
versions of the same product SHOULD only differ in the product- versions of the same product SHOULD only differ in the product-
version portion of the product value). version portion of the product value).
3.9. Quality Values 3.9. Quality Values
HTTP content negotiation (Section 12) uses short "floating point" HTTP content negotiation (Section 12) uses short "floating point"
numbers to indicate the relative importance ("weight") of various numbers to indicate the relative importance ("weight") of various
negotiable parameters. A weight is normalized to a real number in negotiable parameters. A weight is normalized to a real number in
the range 0 through 1, where 0 is the minimum and 1 the maximum the range 0 through 1, where 0 is the minimum and 1 the maximum
value. If a parameter has a quality value of 0, then content with value. If a parameter has a quality value of 0, then content with
this parameter is `not acceptable' for the client. HTTP/1.1 this parameter is `not acceptable' for the client. HTTP/1.1
applications MUST NOT generate more than three digits after the applications MUST NOT generate more than three digits after the
decimal point. User configuration of these values SHOULD also be decimal point. User configuration of these values SHOULD also be
limited in this fashion. limited in this fashion.
qvalue = ( "0" [ "." 0*3DIGIT ] ) qvalue = ( "0" [ "." 0*3DIGIT ] )
| ( "1" [ "." 0*3("0") ] ) | ( "1" [ "." 0*3("0") ] )
"Quality values" is a misnomer, since these values merely represent "Quality values" is a misnomer, since these values merely represent
relative degradation in desired quality. relative degradation in desired quality.
3.10. Language Tags 3.10. Language Tags
A language tag identifies a natural language spoken, written, or A language tag identifies a natural language spoken, written, or
otherwise conveyed by human beings for communication of information otherwise conveyed by human beings for communication of information
to other human beings. Computer languages are explicitly excluded. to other human beings. Computer languages are explicitly excluded.
HTTP uses language tags within the Accept-Language and Content- HTTP uses language tags within the Accept-Language and Content-
Language fields. Language fields.
The syntax and registry of HTTP language tags is the same as that The syntax and registry of HTTP language tags is the same as that
defined by RFC 1766 [1]. In summary, a language tag is composed of 1 defined by RFC 1766 [1]. In summary, a language tag is composed of 1
or more parts: A primary language tag and a possibly empty series of or more parts: A primary language tag and a possibly empty series of
subtags: subtags:
language-tag = primary-tag *( "-" subtag ) language-tag = primary-tag *( "-" subtag )
primary-tag = 1*8ALPHA primary-tag = 1*8ALPHA
subtag = 1*8ALPHA subtag = 1*8ALPHA
White space is not allowed within the tag and all tags are case- White space is not allowed within the tag and all tags are case-
insensitive. The name space of language tags is administered by the insensitive. The name space of language tags is administered by the
IANA. Example tags include: IANA. Example tags include:
en, en-US, en-cockney, i-cherokee, x-pig-latin en, en-US, en-cockney, i-cherokee, x-pig-latin
where any two-letter primary-tag is an ISO-639 language abbreviation where any two-letter primary-tag is an ISO-639 language abbreviation
and any two-letter initial subtag is an ISO-3166 country code. (The and any two-letter initial subtag is an ISO-3166 country code. (The
last three tags above are not registered tags; all but the last are last three tags above are not registered tags; all but the last are
examples of tags which could be registered in future.) examples of tags which could be registered in future.)
3.11. Entity Tags 3.11. Entity Tags
Entity tags are used for comparing two or more entities from the same Entity tags are used for comparing two or more entities from the same
requested resource. HTTP/1.1 uses entity tags in the ETag requested resource. HTTP/1.1 uses entity tags in the ETag
(Section 14.19), If-Match (Section 14.24), If-None-Match (Section 14.19), If-Match (Section 14.24), If-None-Match
(Section 14.26), and If-Range (Section 14.27) header fields. The (Section 14.26), and If-Range (Section 14.27) header fields. The
definition of how they are used and compared as cache validators is definition of how they are used and compared as cache validators is
in Section 13.3.3. An entity tag consists of an opaque quoted in Section 13.3.3. An entity tag consists of an opaque quoted
string, possibly prefixed by a weakness indicator. string, possibly prefixed by a weakness indicator.
entity-tag = [ weak ] opaque-tag entity-tag = [ weak ] opaque-tag
weak = "W/" weak = "W/"
opaque-tag = quoted-string opaque-tag = quoted-string
A "strong entity tag" MAY be shared by two entities of a resource A "strong entity tag" MAY be shared by two entities of a resource
only if they are equivalent by octet equality. only if they are equivalent by octet equality.
A "weak entity tag," indicated by the "W/" prefix, MAY be shared by A "weak entity tag," indicated by the "W/" prefix, MAY be shared by
two entities of a resource only if the entities are equivalent and two entities of a resource only if the entities are equivalent and
could be substituted for each other with no significant change in could be substituted for each other with no significant change in
semantics. A weak entity tag can only be used for weak comparison. semantics. A weak entity tag can only be used for weak comparison.
An entity tag MUST be unique across all versions of all entities An entity tag MUST be unique across all versions of all entities
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entities. entities.
3.12. Range Units 3.12. Range Units
HTTP/1.1 allows a client to request that only part (a range of) the HTTP/1.1 allows a client to request that only part (a range of) the
response entity be included within the response. HTTP/1.1 uses range response entity be included within the response. HTTP/1.1 uses range
units in the Range (Section 14.35) and Content-Range (Section 14.16) units in the Range (Section 14.35) and Content-Range (Section 14.16)
header fields. An entity can be broken down into subranges according header fields. An entity can be broken down into subranges according
to various structural units. to various structural units.
range-unit = bytes-unit | other-range-unit range-unit = bytes-unit | other-range-unit
bytes-unit = "bytes" bytes-unit = "bytes"
other-range-unit = token other-range-unit = token
The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1 The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
implementations MAY ignore ranges specified using other units. implementations MAY ignore ranges specified using other units.
HTTP/1.1 has been designed to allow implementations of applications HTTP/1.1 has been designed to allow implementations of applications
that do not depend on knowledge of ranges. that do not depend on knowledge of ranges.
4. HTTP Message 4. HTTP Message
4.1. Message Types 4.1. Message Types
HTTP messages consist of requests from client to server and responses HTTP messages consist of requests from client to server and responses
from server to client. from server to client.
HTTP-message = Request | Response ; HTTP/1.1 messages HTTP-message = Request | Response ; HTTP/1.1 messages
Request (Section 5) and Response (Section 6) messages use the generic Request (Section 5) and Response (Section 6) messages use the generic
message format of RFC 822 [9] for transferring entities (the payload message format of RFC 822 [9] for transferring entities (the payload
of the message). Both types of message consist of a start-line, zero of the message). Both types of message consist of a start-line, zero
or more header fields (also known as "headers"), an empty line (i.e., or more header fields (also known as "headers"), an empty line (i.e.,
a line with nothing preceding the CRLF) indicating the end of the a line with nothing preceding the CRLF) indicating the end of the
header fields, and possibly a message-body. header fields, and possibly a message-body.
generic-message = start-line generic-message = start-line
*(message-header CRLF) *(message-header CRLF)
CRLF CRLF
[ message-body ] [ message-body ]
start-line = Request-Line | Status-Line start-line = Request-Line | Status-Line
In the interest of robustness, servers SHOULD ignore any empty In the interest of robustness, servers SHOULD ignore any empty
line(s) received where a Request-Line is expected. In other words, line(s) received where a Request-Line is expected. In other words,
if the server is reading the protocol stream at the beginning of a if the server is reading the protocol stream at the beginning of a
message and receives a CRLF first, it should ignore the CRLF. message and receives a CRLF first, it should ignore the CRLF.
Certain buggy HTTP/1.0 client implementations generate extra CRLF's Certain buggy HTTP/1.0 client implementations generate extra CRLF's
after a POST request. To restate what is explicitly forbidden by the after a POST request. To restate what is explicitly forbidden by the
BNF, an HTTP/1.1 client MUST NOT preface or follow a request with an BNF, an HTTP/1.1 client MUST NOT preface or follow a request with an
extra CRLF. extra CRLF.
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that given in Section 3.1 of RFC 822 [9]. Each header field consists that given in Section 3.1 of RFC 822 [9]. Each header field consists
of a name followed by a colon (":") and the field value. Field names of a name followed by a colon (":") and the field value. Field names
are case-insensitive. The field value MAY be preceded by any amount are case-insensitive. The field value MAY be preceded by any amount
of LWS, though a single SP is preferred. Header fields can be of LWS, though a single SP is preferred. Header fields can be
extended over multiple lines by preceding each extra line with at extended over multiple lines by preceding each extra line with at
least one SP or HT. Applications ought to follow "common form", least one SP or HT. Applications ought to follow "common form",
where one is known or indicated, when generating HTTP constructs, where one is known or indicated, when generating HTTP constructs,
since there might exist some implementations that fail to accept since there might exist some implementations that fail to accept
anything beyond the common forms. anything beyond the common forms.
message-header = field-name ":" [ field-value ] message-header = field-name ":" [ field-value ]
field-name = token field-name = token
field-value = *( field-content | LWS ) field-value = *( field-content | LWS )
field-content = <the OCTETs making up the field-value field-content = <the OCTETs making up the field-value
and consisting of either *TEXT or combinations and consisting of either *TEXT or combinations
of token, separators, and quoted-string> of token, separators, and quoted-string>
The field-content does not include any leading or trailing LWS: The field-content does not include any leading or trailing LWS:
linear white space occurring before the first non-whitespace linear white space occurring before the first non-whitespace
character of the field-value or after the last non-whitespace character of the field-value or after the last non-whitespace
character of the field-value. Such leading or trailing LWS MAY be character of the field-value. Such leading or trailing LWS MAY be
removed without changing the semantics of the field value. Any LWS removed without changing the semantics of the field value. Any LWS
that occurs between field-content MAY be replaced with a single SP that occurs between field-content MAY be replaced with a single SP
before interpreting the field value or forwarding the message before interpreting the field value or forwarding the message
downstream. downstream.
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change the order of these field values when a message is forwarded. change the order of these field values when a message is forwarded.
4.3. Message Body 4.3. Message Body
The message-body (if any) of an HTTP message is used to carry the The message-body (if any) of an HTTP message is used to carry the
entity-body associated with the request or response. The message- entity-body associated with the request or response. The message-
body differs from the entity-body only when a transfer-coding has body differs from the entity-body only when a transfer-coding has
been applied, as indicated by the Transfer-Encoding header field been applied, as indicated by the Transfer-Encoding header field
(Section 14.41). (Section 14.41).
message-body = entity-body message-body = entity-body
| <entity-body encoded as per Transfer-Encoding> | <entity-body encoded as per Transfer-Encoding>
Transfer-Encoding MUST be used to indicate any transfer-codings Transfer-Encoding MUST be used to indicate any transfer-codings
applied by an application to ensure safe and proper transfer of the applied by an application to ensure safe and proper transfer of the
message. Transfer-Encoding is a property of the message, not of the message. Transfer-Encoding is a property of the message, not of the
entity, and thus MAY be added or removed by any application along the entity, and thus MAY be added or removed by any application along the
request/response chain. (However, Section 3.6 places restrictions on request/response chain. (However, Section 3.6 places restrictions on
when certain transfer-codings may be used.) when certain transfer-codings may be used.)
The rules for when a message-body is allowed in a message differ for The rules for when a message-body is allowed in a message differ for
requests and responses. requests and responses.
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been applied. When a message-body is included with a message, the been applied. When a message-body is included with a message, the
transfer-length of that body is determined by one of the following transfer-length of that body is determined by one of the following
(in order of precedence): (in order of precedence):
1. Any response message which "MUST NOT" include a message-body 1. Any response message which "MUST NOT" include a message-body
(such as the 1xx, 204, and 304 responses and any response to a (such as the 1xx, 204, and 304 responses and any response to a
HEAD request) is always terminated by the first empty line after HEAD request) is always terminated by the first empty line after
the header fields, regardless of the entity-header fields present the header fields, regardless of the entity-header fields present
in the message. in the message.
2. If a Transfer-Encoding header field (Section 14.41) is present 2. If a Transfer-Encoding header field (Section 14.41) is present,
and has any value other than "identity", then the transfer-length then the transfer-length is defined by use of the "chunked"
is defined by use of the "chunked" transfer-coding (Section 3.6), transfer-coding (Section 3.6), unless the message is terminated
unless the message is terminated by closing the connection. by closing the connection.
3. If a Content-Length header field (Section 14.13) is present, its 3. If a Content-Length header field (Section 14.13) is present, its
decimal value in OCTETs represents both the entity-length and the decimal value in OCTETs represents both the entity-length and the
transfer-length. The Content-Length header field MUST NOT be transfer-length. The Content-Length header field MUST NOT be
sent if these two lengths are different (i.e., if a Transfer- sent if these two lengths are different (i.e., if a Transfer-
Encoding header field is present). If a message is received with Encoding header field is present). If a message is received with
both a Transfer-Encoding header field and a Content-Length header both a Transfer-Encoding header field and a Content-Length header
field, the latter MUST be ignored. field, the latter MUST be ignored.
4. If the message uses the media type "multipart/byteranges", and 4. If the message uses the media type "multipart/byteranges", and
the ransfer-length is not otherwise specified, then this self- the transfer-length is not otherwise specified, then this self-
elimiting media type defines the transfer-length. This media delimiting media type defines the transfer-length. This media
type UST NOT be used unless the sender knows that the recipient type MUST NOT be used unless the sender knows that the recipient
can arse it; the presence in a request of a Range header with can parse it; the presence in a request of a Range header with
ultiple byte-range specifiers from a 1.1 client implies that the multiple byte-range specifiers from a 1.1 client implies that the
lient can parse multipart/byteranges responses. client can parse multipart/byteranges responses.
A range header might be forwarded by a 1.0 proxy that does not A range header might be forwarded by a 1.0 proxy that does not
understand multipart/byteranges; in this case the server MUST understand multipart/byteranges; in this case the server MUST
delimit the message using methods defined in items 1, 3 or 5 delimit the message using methods defined in items 1, 3 or 5
of this section. of this section.
5. By the server closing the connection. (Closing the connection 5. By the server closing the connection. (Closing the connection
cannot be used to indicate the end of a request body, since that cannot be used to indicate the end of a request body, since that
would leave no possibility for the server to send back a would leave no possibility for the server to send back a
response.) response.)
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the server SHOULD respond with 400 (bad request) if it cannot the server SHOULD respond with 400 (bad request) if it cannot
determine the length of the message, or with 411 (length required) if determine the length of the message, or with 411 (length required) if
it wishes to insist on receiving a valid Content-Length. it wishes to insist on receiving a valid Content-Length.
All HTTP/1.1 applications that receive entities MUST accept the All HTTP/1.1 applications that receive entities MUST accept the
"chunked" transfer-coding (Section 3.6), thus allowing this mechanism "chunked" transfer-coding (Section 3.6), thus allowing this mechanism
to be used for messages when the message length cannot be determined to be used for messages when the message length cannot be determined
in advance. in advance.
Messages MUST NOT include both a Content-Length header field and a Messages MUST NOT include both a Content-Length header field and a
non-identity transfer-coding. If the message does include a non- transfer-coding. If the message does include a transfer-coding, the
identity transfer-coding, the Content-Length MUST be ignored. Content-Length MUST be ignored.
When a Content-Length is given in a message where a message-body is When a Content-Length is given in a message where a message-body is
allowed, its field value MUST exactly match the number of OCTETs in allowed, its field value MUST exactly match the number of OCTETs in
the message-body. HTTP/1.1 user agents MUST notify the user when an the message-body. HTTP/1.1 user agents MUST notify the user when an
invalid length is received and detected. invalid length is received and detected.
4.5. General Header Fields 4.5. General Header Fields
There are a few header fields which have general applicability for There are a few header fields which have general applicability for
both request and response messages, but which do not apply to the both request and response messages, but which do not apply to the
entity being transferred. These header fields apply only to the entity being transferred. These header fields apply only to the
message being transmitted. message being transmitted.
general-header = Cache-Control ; Section 14.9 general-header = Cache-Control ; Section 14.9
| Connection ; Section 14.10 | Connection ; Section 14.10
| Date ; Section 14.18 | Date ; Section 14.18
| Pragma ; Section 14.32 | Pragma ; Section 14.32
| Trailer ; Section 14.40 | Trailer ; Section 14.40
| Transfer-Encoding ; Section 14.41 | Transfer-Encoding ; Section 14.41
| Upgrade ; Section 14.42 | Upgrade ; Section 14.42
| Via ; Section 14.45 | Via ; Section 14.45
| Warning ; Section 14.46 | Warning ; Section 14.46
General-header field names can be extended reliably only in General-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or combination with a change in the protocol version. However, new or
experimental header fields may be given the semantics of general experimental header fields may be given the semantics of general
header fields if all parties in the communication recognize them to header fields if all parties in the communication recognize them to
be general-header fields. Unrecognized header fields are treated as be general-header fields. Unrecognized header fields are treated as
entity-header fields. entity-header fields.
5. Request 5. Request
A request message from a client to a server includes, within the A request message from a client to a server includes, within the
first line of that message, the method to be applied to the resource, first line of that message, the method to be applied to the resource,
the identifier of the resource, and the protocol version in use. the identifier of the resource, and the protocol version in use.
Request = Request-Line ; Section 5.1 Request = Request-Line ; Section 5.1
*(( general-header ; Section 4.5 *(( general-header ; Section 4.5
| request-header ; Section 5.3 | request-header ; Section 5.3
| entity-header ) CRLF) ; Section 7.1 | entity-header ) CRLF) ; Section 7.1
CRLF CRLF
[ message-body ] ; Section 4.3 [ message-body ] ; Section 4.3
5.1. Request-Line 5.1. Request-Line
The Request-Line begins with a method token, followed by the Request- The Request-Line begins with a method token, followed by the Request-
URI and the protocol version, and ending with CRLF. The elements are URI and the protocol version, and ending with CRLF. The elements are
separated by SP characters. No CR or LF is allowed except in the separated by SP characters. No CR or LF is allowed except in the
final CRLF sequence. final CRLF sequence.
Request-Line = Method SP Request-URI SP HTTP-Version CRLF Request-Line = Method SP Request-URI SP HTTP-Version CRLF
5.1.1. Method 5.1.1. Method
The Method token indicates the method to be performed on the resource The Method token indicates the method to be performed on the resource
identified by the Request-URI. The method is case-sensitive. identified by the Request-URI. The method is case-sensitive.
Method = "OPTIONS" ; Section 9.2 Method = "OPTIONS" ; Section 9.2
| "GET" ; Section 9.3 | "GET" ; Section 9.3
| "HEAD" ; Section 9.4 | "HEAD" ; Section 9.4
| "POST" ; Section 9.5 | "POST" ; Section 9.5
| "PUT" ; Section 9.6 | "PUT" ; Section 9.6
| "DELETE" ; Section 9.7 | "DELETE" ; Section 9.7
| "TRACE" ; Section 9.8 | "TRACE" ; Section 9.8
| "CONNECT" ; Section 9.9 | "CONNECT" ; Section 9.9
| extension-method | extension-method
extension-method = token extension-method = token
The list of methods allowed by a resource can be specified in an The list of methods allowed by a resource can be specified in an
Allow header field (Section 14.7). The return code of the response Allow header field (Section 14.7). The return code of the response
always notifies the client whether a method is currently allowed on a always notifies the client whether a method is currently allowed on a
resource, since the set of allowed methods can change dynamically. resource, since the set of allowed methods can change dynamically.
An origin server SHOULD return the status code 405 (Method Not An origin server SHOULD return the status code 405 (Method Not
Allowed) if the method is known by the origin server but not allowed Allowed) if the method is known by the origin server but not allowed
for the requested resource, and 501 (Not Implemented) if the method for the requested resource, and 501 (Not Implemented) if the method
is unrecognized or not implemented by the origin server. The methods is unrecognized or not implemented by the origin server. The methods
GET and HEAD MUST be supported by all general-purpose servers. All GET and HEAD MUST be supported by all general-purpose servers. All
other methods are OPTIONAL; however, if the above methods are other methods are OPTIONAL; however, if the above methods are
implemented, they MUST be implemented with the same semantics as implemented, they MUST be implemented with the same semantics as
those specified in Section 9. those specified in Section 9.
5.1.2. Request-URI 5.1.2. Request-URI
The Request-URI is a Uniform Resource Identifier (Section 3.2) and The Request-URI is a Uniform Resource Identifier (Section 3.2) and
identifies the resource upon which to apply the request. identifies the resource upon which to apply the request.
Request-URI = "*" | absoluteURI | abs_path | authority Request-URI = "*"
| absoluteURI
| abs_path [ "?" query ]
| authority
The four options for Request-URI are dependent on the nature of the The four options for Request-URI are dependent on the nature of the
request. The asterisk "*" means that the request does not apply to a request. The asterisk "*" means that the request does not apply to a
particular resource, but to the server itself, and is only allowed particular resource, but to the server itself, and is only allowed
when the method used does not necessarily apply to a resource. One when the method used does not necessarily apply to a resource. One
example would be example would be
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
The absoluteURI form is REQUIRED when the request is being made to a The absoluteURI form is REQUIRED when the request is being made to a
proxy. The proxy is requested to forward the request or service it proxy. The proxy is requested to forward the request or service it
from a valid cache, and return the response. Note that the proxy MAY from a valid cache, and return the response. Note that the proxy MAY
forward the request on to another proxy or directly to the server forward the request on to another proxy or directly to the server
specified by the absoluteURI. In order to avoid request loops, a specified by the absoluteURI. In order to avoid request loops, a
proxy MUST be able to recognize all of its server names, including proxy MUST be able to recognize all of its server names, including
any aliases, local variations, and the numeric IP address. An any aliases, local variations, and the numeric IP address. An
example Request-Line would be: example Request-Line would be:
GET http://www.w3.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
To allow for transition to absoluteURIs in all requests in future To allow for transition to absoluteURIs in all requests in future
versions of HTTP, all HTTP/1.1 servers MUST accept the absoluteURI versions of HTTP, all HTTP/1.1 servers MUST accept the absoluteURI
form in requests, even though HTTP/1.1 clients will only generate form in requests, even though HTTP/1.1 clients will only generate
them in requests to proxies. them in requests to proxies.
The authority form is only used by the CONNECT method (Section 9.9). The authority form is only used by the CONNECT method (Section 9.9).
The most common form of Request-URI is that used to identify a The most common form of Request-URI is that used to identify a
resource on an origin server or gateway. In this case the absolute resource on an origin server or gateway. In this case the absolute
path of the URI MUST be transmitted (see Section 3.2.1, abs_path) as path of the URI MUST be transmitted (see Section 3.2.1, abs_path) as
the Request-URI, and the network location of the URI (authority) MUST the Request-URI, and the network location of the URI (authority) MUST
be transmitted in a Host header field. For example, a client wishing be transmitted in a Host header field. For example, a client wishing
to retrieve the resource above directly from the origin server would to retrieve the resource above directly from the origin server would
create a TCP connection to port 80 of the host "www.w3.org" and send create a TCP connection to port 80 of the host "www.example.org" and
the lines: send the lines:
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.w3.org Host: www.example.org
followed by the remainder of the Request. Note that the absolute followed by the remainder of the Request. Note that the absolute
path cannot be empty; if none is present in the original URI, it MUST path cannot be empty; if none is present in the original URI, it MUST
be given as "/" (the server root). be given as "/" (the server root).
The Request-URI is transmitted in the format specified in section The Request-URI is transmitted in the format specified in
3.2.1. If the Request-URI is encoded using the "% HEX HEX" encoding Section 3.2.1. If the Request-URI is encoded using the "% HEX HEX"
[42], the origin server MUST decode the Request-URI in order to encoding [42], the origin server MUST decode the Request-URI in order
properly interpret the request. Servers SHOULD respond to invalid to properly interpret the request. Servers SHOULD respond to invalid
Request-URIs with an appropriate status code. Request-URIs with an appropriate status code.
A transparent proxy MUST NOT rewrite the "abs_path" part of the A transparent proxy MUST NOT rewrite the "abs_path" part of the
received Request-URI when forwarding it to the next inbound server, received Request-URI when forwarding it to the next inbound server,
except as noted above to replace a null abs_path with "/". except as noted above to replace a null abs_path with "/".
Note: The "no rewrite" rule prevents the proxy from changing the Note: The "no rewrite" rule prevents the proxy from changing the
meaning of the request when the origin server is improperly using meaning of the request when the origin server is improperly using
a non-reserved URI character for a reserved purpose. Implementors a non-reserved URI character for a reserved purpose. Implementors
should be aware that some pre-HTTP/1.1 proxies have been known to should be aware that some pre-HTTP/1.1 proxies have been known to
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exact resource is being requested. exact resource is being requested.
5.3. Request Header Fields 5.3. Request Header Fields
The request-header fields allow the client to pass additional The request-header fields allow the client to pass additional
information about the request, and about the client itself, to the information about the request, and about the client itself, to the
server. These fields act as request modifiers, with semantics server. These fields act as request modifiers, with semantics
equivalent to the parameters on a programming language method equivalent to the parameters on a programming language method
invocation. invocation.
request-header = Accept ; Section 14.1 request-header = Accept ; Section 14.1
| Accept-Charset ; Section 14.2 | Accept-Charset ; Section 14.2
| Accept-Encoding ; Section 14.3 | Accept-Encoding ; Section 14.3
| Accept-Language ; Section 14.4 | Accept-Language ; Section 14.4
| Authorization ; Section 14.8 | Authorization ; Section 14.8
| Expect ; Section 14.20 | Expect ; Section 14.20
| From ; Section 14.22 | From ; Section 14.22
| Host ; Section 14.23 | Host ; Section 14.23
| If-Match ; Section 14.24 | If-Match ; Section 14.24
| If-Modified-Since ; Section 14.25 | If-Modified-Since ; Section 14.25
| If-None-Match ; Section 14.26 | If-None-Match ; Section 14.26
| If-Range ; Section 14.27 | If-Range ; Section 14.27
| If-Unmodified-Since ; Section 14.28 | If-Unmodified-Since ; Section 14.28
| Max-Forwards ; Section 14.31 | Max-Forwards ; Section 14.31
| Proxy-Authorization ; Section 14.34 | Proxy-Authorization ; Section 14.34
| Range ; Section 14.35 | Range ; Section 14.35
| Referer ; Section 14.36 | Referer ; Section 14.36
| TE ; Section 14.39 | TE ; Section 14.39
| User-Agent ; Section 14.43 | User-Agent ; Section 14.43
Request-header field names can be extended reliably only in Request-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or combination with a change in the protocol version. However, new or
experimental header fields MAY be given the semantics of request- experimental header fields MAY be given the semantics of request-
header fields if all parties in the communication recognize them to header fields if all parties in the communication recognize them to
be request-header fields. Unrecognized header fields are treated as be request-header fields. Unrecognized header fields are treated as
entity-header fields. entity-header fields.
6. Response 6. Response
After receiving and interpreting a request message, a server responds After receiving and interpreting a request message, a server responds
with an HTTP response message. with an HTTP response message.
Response = Status-Line ; Section 6.1 Response = Status-Line ; Section 6.1
*(( general-header ; Section 4.5 *(( general-header ; Section 4.5
| response-header ; Section 6.2 | response-header ; Section 6.2
| entity-header ) CRLF) ; Section 7.1 | entity-header ) CRLF) ; Section 7.1
CRLF CRLF
[ message-body ] ; Section 7.2 [ message-body ] ; Section 7.2
6.1. Status-Line 6.1. Status-Line
The first line of a Response message is the Status-Line, consisting The first line of a Response message is the Status-Line, consisting
of the protocol version followed by a numeric status code and its of the protocol version followed by a numeric status code and its
associated textual phrase, with each element separated by SP associated textual phrase, with each element separated by SP
characters. No CR or LF is allowed except in the final CRLF characters. No CR or LF is allowed except in the final CRLF
sequence. sequence.
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
6.1.1. Status Code and Reason Phrase 6.1.1. Status Code and Reason Phrase
The Status-Code element is a 3-digit integer result code of the The Status-Code element is a 3-digit integer result code of the
attempt to understand and satisfy the request. These codes are fully attempt to understand and satisfy the request. These codes are fully
defined in Section 10. The Reason-Phrase is intended to give a short defined in Section 10. The Reason-Phrase is intended to give a short
textual description of the Status-Code. The Status-Code is intended textual description of the Status-Code. The Status-Code is intended
for use by automata and the Reason-Phrase is intended for the human for use by automata and the Reason-Phrase is intended for the human
user. The client is not required to examine or display the Reason- user. The client is not required to examine or display the Reason-
Phrase. Phrase.
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o 5xx: Server Error - The server failed to fulfill an apparently o 5xx: Server Error - The server failed to fulfill an apparently
valid request valid request
The individual values of the numeric status codes defined for The individual values of the numeric status codes defined for
HTTP/1.1, and an example set of corresponding Reason-Phrase's, are HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
presented below. The reason phrases listed here are only presented below. The reason phrases listed here are only
recommendations -- they MAY be replaced by local equivalents without recommendations -- they MAY be replaced by local equivalents without
affecting the protocol. affecting the protocol.
Status-Code = Status-Code =
"100" ; Section 10.1.1: Continue "100" ; Section 10.1.1: Continue
| "101" ; Section 10.1.2: Switching Protocols | "101" ; Section 10.1.2: Switching Protocols
| "200" ; Section 10.2.1: OK | "200" ; Section 10.2.1: OK
| "201" ; Section 10.2.2: Created | "201" ; Section 10.2.2: Created
| "202" ; Section 10.2.3: Accepted | "202" ; Section 10.2.3: Accepted
| "203" ; Section 10.2.4: Non-Authoritative Information | "203" ; Section 10.2.4: Non-Authoritative Information
| "204" ; Section 10.2.5: No Content | "204" ; Section 10.2.5: No Content
| "205" ; Section 10.2.6: Reset Content | "205" ; Section 10.2.6: Reset Content
| "206" ; Section 10.2.7 Partial Content | "206" ; Section 10.2.7: Partial Content
| "300" ; Section 10.3.1: Multiple Choices | "300" ; Section 10.3.1: Multiple Choices
| "301" ; Section 10.3.2: Moved Permanently | "301" ; Section 10.3.2: Moved Permanently
| "302" ; Section 10.3.3: Found | "302" ; Section 10.3.3: Found
| "303" ; Section 10.3.4: See Other | "303" ; Section 10.3.4: See Other
| "304" ; Section 10.3.5: Not Modified | "304" ; Section 10.3.5: Not Modified
| "305" ; Section 10.3.6: Use Proxy | "305" ; Section 10.3.6: Use Proxy
| "307" ; Section 10.3.8: Temporary Redirect | "307" ; Section 10.3.8: Temporary Redirect
| "400" ; Section 10.4.1: Bad Request | "400" ; Section 10.4.1: Bad Request
| "401" ; Section 10.4.2: Unauthorized | "401" ; Section 10.4.2: Unauthorized
| "402" ; Section 10.4.3: Payment Required | "402" ; Section 10.4.3: Payment Required
| "403" ; Section 10.4.4: Forbidden | "403" ; Section 10.4.4: Forbidden
| "404" ; Section 10.4.5: Not Found | "404" ; Section 10.4.5: Not Found
| "405" ; Section 10.4.6: Method Not Allowed | "405" ; Section 10.4.6: Method Not Allowed
| "406" ; Section 10.4.7: Not Acceptable | "406" ; Section 10.4.7: Not Acceptable
| "407" ; Section 10.4.8: Proxy Authentication Required | "407" ; Section 10.4.8: Proxy Authentication Required
| "408" ; Section 10.4.9: Request Time-out | "408" ; Section 10.4.9: Request Time-out
| "409" ; Section 10.4.10: Conflict | "409" ; Section 10.4.10: Conflict
| "410" ; Section 10.4.11: Gone | "410" ; Section 10.4.11: Gone
| "411" ; Section 10.4.12: Length Required | "411" ; Section 10.4.12: Length Required
| "412" ; Section 10.4.13: Precondition Failed | "412" ; Section 10.4.13: Precondition Failed
| "413" ; Section 10.4.14: Request Entity Too Large | "413" ; Section 10.4.14: Request Entity Too Large
| "414" ; Section 10.4.15: Request-URI Too Large | "414" ; Section 10.4.15: Request-URI Too Large
| "415" ; Section 10.4.16: Unsupported Media Type | "415" ; Section 10.4.16: Unsupported Media Type
| "416" ; Section 10.4.17: Requested range not satisfiable | "416" ; Section 10.4.17: Requested range not satisfiable
| "417" ; Section 10.4.18: Expectation Failed | "417" ; Section 10.4.18: Expectation Failed
| "500" ; Section 10.5.1: Internal Server Error | "500" ; Section 10.5.1: Internal Server Error
| "501" ; Section 10.5.2: Not Implemented | "501" ; Section 10.5.2: Not Implemented
| "502" ; Section 10.5.3: Bad Gateway | "502" ; Section 10.5.3: Bad Gateway
| "503" ; Section 10.5.4: Service Unavailable | "503" ; Section 10.5.4: Service Unavailable
| "504" ; Section 10.5.5: Gateway Time-out | "504" ; Section 10.5.5: Gateway Time-out
| "505" ; Section 10.5.6: HTTP Version not supported | "505" ; Section 10.5.6: HTTP Version not supported
| extension-code | extension-code
extension-code = 3DIGIT extension-code = 3DIGIT
Reason-Phrase = *<TEXT, excluding CR, LF> Reason-Phrase = *<TEXT, excluding CR, LF>
HTTP status codes are extensible. HTTP applications are not required HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an x00 status code of that class, with the exception that an
unrecognized response MUST NOT be cached. For example, if an unrecognized response MUST NOT be cached. For example, if an
unrecognized status code of 431 is received by the client, it can unrecognized status code of 431 is received by the client, it can
safely assume that there was something wrong with its request and safely assume that there was something wrong with its request and
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with the response, since that entity is likely to include human- with the response, since that entity is likely to include human-
readable information which will explain the unusual status. readable information which will explain the unusual status.
6.2. Response Header Fields 6.2. Response Header Fields
The response-header fields allow the server to pass additional The response-header fields allow the server to pass additional
information about the response which cannot be placed in the Status- information about the response which cannot be placed in the Status-
Line. These header fields give information about the server and Line. These header fields give information about the server and
about further access to the resource identified by the Request-URI. about further access to the resource identified by the Request-URI.
response-header = Accept-Ranges ; Section 14.5 response-header = Accept-Ranges ; Section 14.5
| Age ; Section 14.6 | Age ; Section 14.6
| ETag ; Section 14.19 | ETag ; Section 14.19
| Location ; Section 14.30 | Location ; Section 14.30
| Proxy-Authenticate ; Section 14.33 | Proxy-Authenticate ; Section 14.33
| Retry-After ; Section 14.37 | Retry-After ; Section 14.37
| Server ; Section 14.38 | Server ; Section 14.38
| Vary ; Section 14.44 | Vary ; Section 14.44
| WWW-Authenticate ; Section 14.47 | WWW-Authenticate ; Section 14.47
Response-header field names can be extended reliably only in Response-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or combination with a change in the protocol version. However, new or
experimental header fields MAY be given the semantics of response- experimental header fields MAY be given the semantics of response-
header fields if all parties in the communication recognize them to header fields if all parties in the communication recognize them to
be response-header fields. Unrecognized header fields are treated as be response-header fields. Unrecognized header fields are treated as
entity-header fields. entity-header fields.
7. Entity 7. Entity
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In this section, both sender and recipient refer to either the client In this section, both sender and recipient refer to either the client
or the server, depending on who sends and who receives the entity. or the server, depending on who sends and who receives the entity.
7.1. Entity Header Fields 7.1. Entity Header Fields
Entity-header fields define metainformation about the entity-body or, Entity-header fields define metainformation about the entity-body or,
if no body is present, about the resource identified by the request. if no body is present, about the resource identified by the request.
Some of this metainformation is OPTIONAL; some might be REQUIRED by Some of this metainformation is OPTIONAL; some might be REQUIRED by
portions of this specification. portions of this specification.
entity-header = Allow ; Section 14.7 entity-header = Allow ; Section 14.7
| Content-Encoding ; Section 14.11 | Content-Encoding ; Section 14.11
| Content-Language ; Section 14.12 | Content-Language ; Section 14.12
| Content-Length ; Section 14.13 | Content-Length ; Section 14.13
| Content-Location ; Section 14.14 | Content-Location ; Section 14.14
| Content-MD5 ; Section 14.15 | Content-MD5 ; Section 14.15
| Content-Range ; Section 14.16 | Content-Range ; Section 14.16
| Content-Type ; Section 14.17 | Content-Type ; Section 14.17
| Expires ; Section 14.21 | Expires ; Section 14.21
| Last-Modified ; Section 14.29 | Last-Modified ; Section 14.29
| extension-header | extension-header
extension-header = message-header extension-header = message-header
The extension-header mechanism allows additional entity-header fields The extension-header mechanism allows additional entity-header fields
to be defined without changing the protocol, but these fields cannot to be defined without changing the protocol, but these fields cannot
be assumed to be recognizable by the recipient. Unrecognized header be assumed to be recognizable by the recipient. Unrecognized header
fields SHOULD be ignored by the recipient and MUST be forwarded by fields SHOULD be ignored by the recipient and MUST be forwarded by
transparent proxies. transparent proxies.
7.2. Entity Body 7.2. Entity Body
The entity-body (if any) sent with an HTTP request or response is in The entity-body (if any) sent with an HTTP request or response is in
a format and encoding defined by the entity-header fields. a format and encoding defined by the entity-header fields.
entity-body = *OCTET entity-body = *OCTET
An entity-body is only present in a message when a message-body is An entity-body is only present in a message when a message-body is
present, as described in Section 4.3. The entity-body is obtained present, as described in Section 4.3. The entity-body is obtained
from the message-body by decoding any Transfer-Encoding that might from the message-body by decoding any Transfer-Encoding that might
have been applied to ensure safe and proper transfer of the message. have been applied to ensure safe and proper transfer of the message.
7.2.1. Type 7.2.1. Type
When an entity-body is included with a message, the data type of that When an entity-body is included with a message, the data type of that
body is determined via the header fields Content-Type and Content- body is determined via the header fields Content-Type and Content-
Encoding. These define a two-layer, ordered encoding model: Encoding. These define a two-layer, ordered encoding model:
entity-body := Content-Encoding( Content-Type( data ) ) entity-body := Content-Encoding( Content-Type( data ) )
Content-Type specifies the media type of the underlying data. Content-Type specifies the media type of the underlying data.
Content-Encoding may be used to indicate any additional content Content-Encoding may be used to indicate any additional content
codings applied to the data, usually for the purpose of data codings applied to the data, usually for the purpose of data
compression, that are a property of the requested resource. There is compression, that are a property of the requested resource. There is
no default encoding. no default encoding.
Any HTTP/1.1 message containing an entity-body SHOULD include a Any HTTP/1.1 message containing an entity-body SHOULD include a
Content-Type header field defining the media type of that body. If Content-Type header field defining the media type of that body. If
and only if the media type is not given by a Content-Type field, the and only if the media type is not given by a Content-Type field, the
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information contained in the response MAY be used to update a information contained in the response MAY be used to update a
previously cached entity from that resource. If the new field values previously cached entity from that resource. If the new field values
indicate that the cached entity differs from the current entity (as indicate that the cached entity differs from the current entity (as
would be indicated by a change in Content-Length, Content-MD5, ETag would be indicated by a change in Content-Length, Content-MD5, ETag
or Last-Modified), then the cache MUST treat the cache entry as or Last-Modified), then the cache MUST treat the cache entry as
stale. stale.
9.5. POST 9.5. POST
The POST method is used to request that the origin server accept the The POST method is used to request that the origin server accept the
entity enclosed in the request as a new subordinate of the resource entity enclosed in the request as data to be processed by the
identified by the Request-URI in the Request-Line. POST is designed resource identified by the Request-URI in the Request-Line. POST is
to allow a uniform method to cover the following functions: designed to allow a uniform method to cover the following functions:
o Annotation of existing resources; o Annotation of existing resources;
o Posting a message to a bulletin board, newsgroup, mailing list, or o Posting a message to a bulletin board, newsgroup, mailing list, or
similar group of articles; similar group of articles;
o Providing a block of data, such as the result of submitting a o Providing a block of data, such as the result of submitting a
form, to a data-handling process; form, to a data-handling process;
o Extending a database through an append operation. o Extending a database through an append operation.
The actual function performed by the POST method is determined by the The actual function performed by the POST method is determined by the
server and is usually dependent on the Request-URI. The posted server and is usually dependent on the Request-URI.
entity is subordinate to that URI in the same way that a file is
subordinate to a directory containing it, a news article is
subordinate to a newsgroup to which it is posted, or a record is
subordinate to a database.
The action performed by the POST method might not result in a The action performed by the POST method might not result in a
resource that can be identified by a URI. In this case, either 200 resource that can be identified by a URI. In this case, either 200
(OK) or 204 (No Content) is the appropriate response status, (OK) or 204 (No Content) is the appropriate response status,
depending on whether or not the response includes an entity that depending on whether or not the response includes an entity that
describes the result. describes the result.
If a resource has been created on the origin server, the response If a resource has been created on the origin server, the response
SHOULD be 201 (Created) and contain an entity which describes the SHOULD be 201 (Created) and contain an entity which describes the
status of the request and refers to the new resource, and a Location status of the request and refers to the new resource, and a Location
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o Date o Date
o ETag and/or Content-Location, if the header would have been sent o ETag and/or Content-Location, if the header would have been sent
in a 200 response to the same request in a 200 response to the same request
o Expires, Cache-Control, and/or Vary, if the field-value might o Expires, Cache-Control, and/or Vary, if the field-value might
differ from that sent in any previous response for the same differ from that sent in any previous response for the same
variant variant
If the 206 response is the result of an If-Range request that used a If the 206 response is the result of an If-Range request, the
strong cache validator (see Section 13.3.3), the response SHOULD NOT response SHOULD NOT include other entity-headers. Otherwise, the
include other entity-headers. If the response is the result of an response MUST include all of the entity-headers that would have been
If-Range request that used a weak validator, the response MUST NOT returned with a 200 (OK) response to the same request.
include other entity-headers; this prevents inconsistencies between
cached entity-bodies and updated headers. Otherwise, the response
MUST include all of the entity-headers that would have been returned
with a 200 (OK) response to the same request.
A cache MUST NOT combine a 206 response with other previously cached A cache MUST NOT combine a 206 response with other previously cached
content if the ETag or Last-Modified headers do not match exactly, content if the ETag or Last-Modified headers do not match exactly,
see 13.5.4. see 13.5.4.
A cache that does not support the Range and Content-Range headers A cache that does not support the Range and Content-Range headers
MUST NOT cache 206 (Partial) responses. MUST NOT cache 206 (Partial) responses.
10.3. Redirection 3xx 10.3. Redirection 3xx
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URIs. Clients with link editing capabilities ought to automatically URIs. Clients with link editing capabilities ought to automatically
re-link references to the Request-URI to one or more of the new re-link references to the Request-URI to one or more of the new
references returned by the server, where possible. This response is references returned by the server, where possible. This response is
cacheable unless indicated otherwise. cacheable unless indicated otherwise.
The new permanent URI SHOULD be given by the Location field in the The new permanent URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity of the response. Unless the request method was HEAD, the entity of the
response SHOULD contain a short hypertext note with a hyperlink to response SHOULD contain a short hypertext note with a hyperlink to
the new URI(s). the new URI(s).
If the 301 status code is received in response to a request other If the 301 status code is received in response to a request method
than GET or HEAD, the user agent MUST NOT automatically redirect the that is known to be "safe", as defined in Section 9.1.1, then the
request unless it can be confirmed by the user, since this might request MAY be automatically redirected by the user agent without
change the conditions under which the request was issued. confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued.
Note: When automatically redirecting a POST request after Note: When automatically redirecting a POST request after
receiving a 301 status code, some existing HTTP/1.0 user agents receiving a 301 status code, some existing HTTP/1.0 user agents
will erroneously change it into a GET request. will erroneously change it into a GET request.
10.3.3. 302 Found 10.3.3. 302 Found
The requested resource resides temporarily under a different URI. The requested resource resides temporarily under a different URI.
Since the redirection might be altered on occasion, the client SHOULD Since the redirection might be altered on occasion, the client SHOULD
continue to use the Request-URI for future requests. This response continue to use the Request-URI for future requests. This response
is only cacheable if indicated by a Cache-Control or Expires header is only cacheable if indicated by a Cache-Control or Expires header
field. field.
The temporary URI SHOULD be given by the Location field in the The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity of the response. Unless the request method was HEAD, the entity of the
response SHOULD contain a short hypertext note with a hyperlink to response SHOULD contain a short hypertext note with a hyperlink to
the new URI(s). the new URI(s).
If the 302 status code is received in response to a request other If the 302 status code is received in response to a request method
than GET or HEAD, the user agent MUST NOT automatically redirect the that is known to be "safe", as defined in Section 9.1.1, then the
request unless it can be confirmed by the user, since this might request MAY be automatically redirected by the user agent without
change the conditions under which the request was issued. confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued.
Note: RFC 1945 and RFC 2068 specify that the client is not allowed Note: RFC 1945 and RFC 2068 specify that the client is not allowed
to change the method on the redirected request. However, most to change the method on the redirected request. However, most
existing user agent implementations treat 302 as if it were a 303 existing user agent implementations treat 302 as if it were a 303
response, performing a GET on the Location field-value regardless response, performing a GET on the Location field-value regardless
of the original request method. The status codes 303 and 307 have of the original request method. The status codes 303 and 307 have
been added for servers that wish to make unambiguously clear which been added for servers that wish to make unambiguously clear which
kind of reaction is expected of the client. kind of reaction is expected of the client.
10.3.4. 303 See Other 10.3.4. 303 See Other
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field. field.
The temporary URI SHOULD be given by the Location field in the The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity of the response. Unless the request method was HEAD, the entity of the
response SHOULD contain a short hypertext note with a hyperlink to response SHOULD contain a short hypertext note with a hyperlink to
the new URI(s) , since many pre-HTTP/1.1 user agents do not the new URI(s) , since many pre-HTTP/1.1 user agents do not
understand the 307 status. Therefore, the note SHOULD contain the understand the 307 status. Therefore, the note SHOULD contain the
information necessary for a user to repeat the original request on information necessary for a user to repeat the original request on
the new URI. the new URI.
If the 307 status code is received in response to a request other If the 307 status code is received in response to a request method
than GET or HEAD, the user agent MUST NOT automatically redirect the that is known to be "safe", as defined in Section 9.1.1, then the
request unless it can be confirmed by the user, since this might request MAY be automatically redirected by the user agent without
change the conditions under which the request was issued. confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued.
10.4. Client Error 4xx 10.4. Client Error 4xx
The 4xx class of status code is intended for cases in which the The 4xx class of status code is intended for cases in which the
client seems to have erred. Except when responding to a HEAD client seems to have erred. Except when responding to a HEAD
request, the server SHOULD include an entity containing an request, the server SHOULD include an entity containing an
explanation of the error situation, and whether it is a temporary or explanation of the error situation, and whether it is a temporary or
permanent condition. These status codes are applicable to any permanent condition. These status codes are applicable to any
request method. User agents SHOULD display any included entity to request method. User agents SHOULD display any included entity to
the user. the user.
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1. now minus date_value, if the local clock is reasonably well 1. now minus date_value, if the local clock is reasonably well
synchronized to the origin server's clock. If the result is synchronized to the origin server's clock. If the result is
negative, the result is replaced by zero. negative, the result is replaced by zero.
2. age_value, if all of the caches along the response path implement 2. age_value, if all of the caches along the response path implement
HTTP/1.1. HTTP/1.1.
Given that we have two independent ways to compute the age of a Given that we have two independent ways to compute the age of a
response when it is received, we can combine these as response when it is received, we can combine these as
corrected_received_age = max(now - date_value, age_value) corrected_received_age = max(now - date_value, age_value)
and as long as we have either nearly synchronized clocks or all- and as long as we have either nearly synchronized clocks or all-
HTTP/1.1 paths, one gets a reliable (conservative) result. HTTP/1.1 paths, one gets a reliable (conservative) result.
Because of network-imposed delays, some significant interval might Because of network-imposed delays, some significant interval might
pass between the time that a server generates a response and the time pass between the time that a server generates a response and the time
it is received at the next outbound cache or client. If uncorrected, it is received at the next outbound cache or client. If uncorrected,
this delay could result in improperly low ages. this delay could result in improperly low ages.
Because the request that resulted in the returned Age value must have Because the request that resulted in the returned Age value must have
been initiated prior to that Age value's generation, we can correct been initiated prior to that Age value's generation, we can correct
for delays imposed by the network by recording the time at which the for delays imposed by the network by recording the time at which the
request was initiated. Then, when an Age value is received, it MUST request was initiated. Then, when an Age value is received, it MUST
be interpreted relative to the time the request was initiated, not be interpreted relative to the time the request was initiated, not
the time that the response was received. This algorithm results in the time that the response was received. This algorithm results in
conservative behavior no matter how much delay is experienced. So, conservative behavior no matter how much delay is experienced. So,
we compute: we compute:
corrected_initial_age = corrected_received_age corrected_initial_age = corrected_received_age
+ (now - request_time) + (now - request_time)
where "request_time" is the time (according to the local clock) when where "request_time" is the time (according to the local clock) when
the request that elicited this response was sent. the request that elicited this response was sent.
Summary of age calculation algorithm, when a cache receives a Summary of age calculation algorithm, when a cache receives a
response: response:
/* /*
* age_value * age_value
* is the value of Age: header received by the cache with * is the value of Age: header received by the cache with
* this response. * this response.
* date_value * date_value
* is the value of the origin server's Date: header * is the value of the origin server's Date: header
* request_time * request_time
* is the (local) time when the cache made the request * is the (local) time when the cache made the request
* that resulted in this cached response * that resulted in this cached response
* response_time * response_time
* is the (local) time when the cache received the * is the (local) time when the cache received the
* response * response
* now * now
* is the current (local) time * is the current (local) time
*/ */
apparent_age = max(0, response_time - date_value); apparent_age = max(0, response_time - date_value);
corrected_received_age = max(apparent_age, age_value); corrected_received_age = max(apparent_age, age_value);
response_delay = response_time - request_time; response_delay = response_time - request_time;
corrected_initial_age = corrected_received_age + response_delay; corrected_initial_age = corrected_received_age + response_delay;
resident_time = now - response_time; resident_time = now - response_time;
current_age = corrected_initial_age + resident_time; current_age = corrected_initial_age + resident_time;
The current_age of a cache entry is calculated by adding the amount The current_age of a cache entry is calculated by adding the amount
of time (in seconds) since the cache entry was last validated by the of time (in seconds) since the cache entry was last validated by the
origin server to the corrected_initial_age. When a response is origin server to the corrected_initial_age. When a response is
generated from a cache entry, the cache MUST include a single Age generated from a cache entry, the cache MUST include a single Age
header field in the response with a value equal to the cache entry's header field in the response with a value equal to the cache entry's
current_age. current_age.
The presence of an Age header field in a response implies that a The presence of an Age header field in a response implies that a
response is not first-hand. However, the converse is not true, since response is not first-hand. However, the converse is not true, since
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appropriate for arithmetic operations. appropriate for arithmetic operations.
We use the term "expires_value" to denote the value of the Expires We use the term "expires_value" to denote the value of the Expires
header. We use the term "max_age_value" to denote an appropriate header. We use the term "max_age_value" to denote an appropriate
value of the number of seconds carried by the "max-age" directive of value of the number of seconds carried by the "max-age" directive of
the Cache-Control header in a response (see Section 14.9.3). the Cache-Control header in a response (see Section 14.9.3).
The max-age directive takes priority over Expires, so if max-age is The max-age directive takes priority over Expires, so if max-age is
present in a response, the calculation is simply: present in a response, the calculation is simply:
freshness_lifetime = max_age_value freshness_lifetime = max_age_value
Otherwise, if Expires is present in the response, the calculation is: Otherwise, if Expires is present in the response, the calculation is:
freshness_lifetime = expires_value - date_value freshness_lifetime = expires_value - date_value
Note that neither of these calculations is vulnerable to clock skew, Note that neither of these calculations is vulnerable to clock skew,
since all of the information comes from the origin server. since all of the information comes from the origin server.
If none of Expires, Cache-Control: max-age, or Cache-Control: If none of Expires, Cache-Control: max-age, or Cache-Control:
s-maxage (see Section 14.9.3) appears in the response, and the s-maxage (see Section 14.9.3) appears in the response, and the
response does not include other restrictions on caching, the cache response does not include other restrictions on caching, the cache
MAY compute a freshness lifetime using a heuristic. The cache MUST MAY compute a freshness lifetime using a heuristic. The cache MUST
attach Warning 113 to any response whose age is more than 24 hours if attach Warning 113 to any response whose age is more than 24 hours if
such warning has not already been added. such warning has not already been added.
Also, if the response does have a Last-Modified time, the heuristic Also, if the response does have a Last-Modified time, the heuristic
expiration value SHOULD be no more than some fraction of the interval expiration value SHOULD be no more than some fraction of the interval
since that time. A typical setting of this fraction might be 10%. since that time. A typical setting of this fraction might be 10%.
The calculation to determine if a response has expired is quite The calculation to determine if a response has expired is quite
simple: simple:
response_is_fresh = (freshness_lifetime > current_age) response_is_fresh = (freshness_lifetime > current_age)
13.2.5. Disambiguating Expiration Values 13.2.5. Disambiguating Expiration Values
Because expiration values are assigned optimistically, it is possible Because expiration values are assigned optimistically, it is possible
for two caches to contain fresh values for the same resource that are for two caches to contain fresh values for the same resource that are
different. different.
If a client performing a retrieval receives a non-first-hand response If a client performing a retrieval receives a non-first-hand response
for a request that was already fresh in its own cache, and the Date for a request that was already fresh in its own cache, and the Date
header in its existing cache entry is newer than the Date on the new header in its existing cache entry is newer than the Date on the new
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Neither the entity tag nor the expiration value can impose an Neither the entity tag nor the expiration value can impose an
ordering on responses, since it is possible that a later response ordering on responses, since it is possible that a later response
intentionally carries an earlier expiration time. The Date values intentionally carries an earlier expiration time. The Date values
are ordered to a granularity of one second. are ordered to a granularity of one second.
When a client tries to revalidate a cache entry, and the response it When a client tries to revalidate a cache entry, and the response it
receives contains a Date header that appears to be older than the one receives contains a Date header that appears to be older than the one
for the existing entry, then the client SHOULD repeat the request for the existing entry, then the client SHOULD repeat the request
unconditionally, and include unconditionally, and include
Cache-Control: max-age=0 Cache-Control: max-age=0
to force any intermediate caches to validate their copies directly to force any intermediate caches to validate their copies directly
with the origin server, or with the origin server, or
Cache-Control: no-cache Cache-Control: no-cache
to force any intermediate caches to obtain a new copy from the origin to force any intermediate caches to obtain a new copy from the origin
server. server.
If the Date values are equal, then the client MAY use either response If the Date values are equal, then the client MAY use either response
(or MAY, if it is being extremely prudent, request a new response). (or MAY, if it is being extremely prudent, request a new response).
Servers MUST NOT depend on clients being able to choose Servers MUST NOT depend on clients being able to choose
deterministically between responses generated during the same second, deterministically between responses generated during the same second,
if their expiration times overlap. if their expiration times overlap.
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o Connection o Connection
o Keep-Alive o Keep-Alive
o Proxy-Authenticate o Proxy-Authenticate
o Proxy-Authorization o Proxy-Authorization
o TE o TE
o Trailers o Trailer
o Transfer-Encoding o Transfer-Encoding
o Upgrade o Upgrade
All other headers defined by HTTP/1.1 are end-to-end headers. All other headers defined by HTTP/1.1 are end-to-end headers.
Other hop-by-hop headers MUST be listed in a Connection header, Other hop-by-hop headers MUST be listed in a Connection header,
(Section 14.10) to be introduced into HTTP/1.1 (or later). (Section 14.10) to be introduced into HTTP/1.1 (or later).
skipping to change at page 107, line 11 skipping to change at page 109, line 11
is either the entity referred to by the Request-URI, or by the is either the entity referred to by the Request-URI, or by the
Location or Content-Location headers (if present). These methods Location or Content-Location headers (if present). These methods
are: are:
o PUT o PUT
o DELETE o DELETE
o POST o POST
In order to prevent denial of service attacks, an invalidation based An invalidation based on the URI in a Location or Content-Location
on the URI in a Location or Content-Location header MUST only be header MUST NOT be performed if the host part of that URI differs
performed if the host part is the same as in the Request-URI. from the host part in the Request-URI. This helps prevent denial of
service attacks.
A cache that passes through requests for methods it does not A cache that passes through requests for methods it does not
understand SHOULD invalidate any entities referred to by the Request- understand SHOULD invalidate any entities referred to by the Request-
URI. URI.
13.11. Write-Through Mandatory 13.11. Write-Through Mandatory
All methods that might be expected to cause modifications to the All methods that might be expected to cause modifications to the
origin server's resources MUST be written through to the origin origin server's resources MUST be written through to the origin
server. This currently includes all methods except for GET and HEAD. server. This currently includes all methods except for GET and HEAD.
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sends and who receives the entity. sends and who receives the entity.
14.1. Accept 14.1. Accept
The Accept request-header field can be used to specify certain media The Accept request-header field can be used to specify certain media
types which are acceptable for the response. Accept headers can be types which are acceptable for the response. Accept headers can be
used to indicate that the request is specifically limited to a small used to indicate that the request is specifically limited to a small
set of desired types, as in the case of a request for an in-line set of desired types, as in the case of a request for an in-line
image. image.
Accept = "Accept" ":" Accept = "Accept" ":"
#( media-range [ accept-params ] ) #( media-range [ accept-params ] )
media-range = ( "*/*" media-range = ( "*/*"
| ( type "/" "*" ) | ( type "/" "*" )
| ( type "/" subtype ) | ( type "/" subtype )
) *( ";" parameter ) ) *( ";" parameter )
accept-params = ";" "q" "=" qvalue *( accept-extension ) accept-params = ";" "q" "=" qvalue *( accept-extension )
accept-extension = ";" token [ "=" ( token | quoted-string ) ] accept-extension = ";" token [ "=" ( token | quoted-string ) ]
The asterisk "*" character is used to group media types into ranges, The asterisk "*" character is used to group media types into ranges,
with "*/*" indicating all media types and "type/*" indicating all with "*/*" indicating all media types and "type/*" indicating all
subtypes of that type. The media-range MAY include media type subtypes of that type. The media-range MAY include media type
parameters that are applicable to that range. parameters that are applicable to that range.
Each media-range MAY be followed by one or more accept-params, Each media-range MAY be followed by one or more accept-params,
beginning with the "q" parameter for indicating a relative quality beginning with the "q" parameter for indicating a relative quality
factor. The first "q" parameter (if any) separates the media-range factor. The first "q" parameter (if any) separates the media-range
parameter(s) from the accept-params. Quality factors allow the user parameter(s) from the accept-params. Quality factors allow the user
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Note: Use of the "q" parameter name to separate media type Note: Use of the "q" parameter name to separate media type
parameters from Accept extension parameters is due to historical parameters from Accept extension parameters is due to historical
practice. Although this prevents any media type parameter named practice. Although this prevents any media type parameter named
"q" from being used with a media range, such an event is believed "q" from being used with a media range, such an event is believed
to be unlikely given the lack of any "q" parameters in the IANA to be unlikely given the lack of any "q" parameters in the IANA
media type registry and the rare usage of any media type media type registry and the rare usage of any media type
parameters in Accept. Future media types are discouraged from parameters in Accept. Future media types are discouraged from
registering any parameter named "q". registering any parameter named "q".
The example The example
Accept: audio/*; q=0.2, audio/basic Accept: audio/*; q=0.2, audio/basic
SHOULD be interpreted as "I prefer audio/basic, but send me any audio SHOULD be interpreted as "I prefer audio/basic, but send me any audio
type if it is the best available after an 80% mark-down in quality." type if it is the best available after an 80% mark-down in quality."
If no Accept header field is present, then it is assumed that the If no Accept header field is present, then it is assumed that the
client accepts all media types. If an Accept header field is client accepts all media types. If an Accept header field is
present, and if the server cannot send a response which is acceptable present, and if the server cannot send a response which is acceptable
according to the combined Accept field value, then the server SHOULD according to the combined Accept field value, then the server SHOULD
send a 406 (not acceptable) response. send a 406 (not acceptable) response.
A more elaborate example is A more elaborate example is
Accept: text/plain; q=0.5, text/html, Accept: text/plain; q=0.5, text/html,
text/x-dvi; q=0.8, text/x-c text/x-dvi; q=0.8, text/x-c
Verbally, this would be interpreted as "text/html and text/x-c are Verbally, this would be interpreted as "text/html and text/x-c are
the preferred media types, but if they do not exist, then send the the preferred media types, but if they do not exist, then send the
text/x-dvi entity, and if that does not exist, send the text/plain text/x-dvi entity, and if that does not exist, send the text/plain
entity." entity."
Media ranges can be overridden by more specific media ranges or Media ranges can be overridden by more specific media ranges or
specific media types. If more than one media range applies to a specific media types. If more than one media range applies to a
given type, the most specific reference has precedence. For example, given type, the most specific reference has precedence. For example,
Accept: text/*, text/html, text/html;level=1, */* Accept: text/*, text/html, text/html;level=1, */*
have the following precedence: have the following precedence:
1) text/html;level=1 1) text/html;level=1
2) text/html 2) text/html
3) text/* 3) text/*
4) */* 4) */*
The media type quality factor associated with a given type is The media type quality factor associated with a given type is
determined by finding the media range with the highest precedence determined by finding the media range with the highest precedence
which matches that type. For example, which matches that type. For example,
Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1, Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
text/html;level=2;q=0.4, */*;q=0.5 text/html;level=2;q=0.4, */*;q=0.5
would cause the following values to be associated: would cause the following values to be associated:
text/html;level=1 = 1 text/html;level=1 = 1
text/html = 0.7 text/html = 0.7
text/plain = 0.3 text/plain = 0.3
image/jpeg = 0.5 image/jpeg = 0.5
text/html;level=2 = 0.4 text/html;level=2 = 0.4
text/html;level=3 = 0.7 text/html;level=3 = 0.7
Note: A user agent might be provided with a default set of quality Note: A user agent might be provided with a default set of quality
values for certain media ranges. However, unless the user agent is a values for certain media ranges. However, unless the user agent is a
closed system which cannot interact with other rendering agents, this closed system which cannot interact with other rendering agents, this
default set ought to be configurable by the user. default set ought to be configurable by the user.
14.2. Accept-Charset 14.2. Accept-Charset
The Accept-Charset request-header field can be used to indicate what The Accept-Charset request-header field can be used to indicate what
character sets are acceptable for the response. This field allows character sets are acceptable for the response. This field allows
clients capable of understanding more comprehensive or special- clients capable of understanding more comprehensive or special-
purpose character sets to signal that capability to a server which is purpose character sets to signal that capability to a server which is
capable of representing documents in those character sets. capable of representing documents in those character sets.
Accept-Charset = "Accept-Charset" ":" Accept-Charset = "Accept-Charset" ":"
1#( ( charset | "*" )[ ";" "q" "=" qvalue ] ) 1#( ( charset | "*" )[ ";" "q" "=" qvalue ] )
Character set values are described in Section 3.4. Each charset MAY Character set values are described in Section 3.4. Each charset MAY
be given an associated quality value which represents the user's be given an associated quality value which represents the user's
preference for that charset. The default value is q=1. An example preference for that charset. The default value is q=1. An example
is is
Accept-Charset: iso-8859-5, unicode-1-1;q=0.8 Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
The special value "*", if present in the Accept-Charset field, The special value "*", if present in the Accept-Charset field,
matches every character set (including ISO-8859-1) which is not matches every character set (including ISO-8859-1) which is not
mentioned elsewhere in the Accept-Charset field. If no "*" is mentioned elsewhere in the Accept-Charset field. If no "*" is
present in an Accept-Charset field, then all character sets not present in an Accept-Charset field, then all character sets not
explicitly mentioned get a quality value of 0, except for ISO-8859-1, explicitly mentioned get a quality value of 0, except for ISO-8859-1,
which gets a quality value of 1 if not explicitly mentioned. which gets a quality value of 1 if not explicitly mentioned.
If no Accept-Charset header is present, the default is that any If no Accept-Charset header is present, the default is that any
character set is acceptable. If an Accept-Charset header is present, character set is acceptable. If an Accept-Charset header is present,
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according to the Accept-Charset header, then the server SHOULD send according to the Accept-Charset header, then the server SHOULD send
an error response with the 406 (not acceptable) status code, though an error response with the 406 (not acceptable) status code, though
the sending of an unacceptable response is also allowed. the sending of an unacceptable response is also allowed.
14.3. Accept-Encoding 14.3. Accept-Encoding
The Accept-Encoding request-header field is similar to Accept, but The Accept-Encoding request-header field is similar to Accept, but
restricts the content-codings (Section 3.5) that are acceptable in restricts the content-codings (Section 3.5) that are acceptable in
the response. the response.
Accept-Encoding = "Accept-Encoding" ":" Accept-Encoding = "Accept-Encoding" ":"
1#( codings [ ";" "q" "=" qvalue ] ) 1#( codings [ ";" "q" "=" qvalue ] )
codings = ( content-coding | "*" ) codings = ( content-coding | "*" )
Examples of its use are: Examples of its use are:
Accept-Encoding: compress, gzip Accept-Encoding: compress, gzip
Accept-Encoding: Accept-Encoding:
Accept-Encoding: * Accept-Encoding: *
Accept-Encoding: compress;q=0.5, gzip;q=1.0 Accept-Encoding: compress;q=0.5, gzip;q=1.0
Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0 Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
A server tests whether a content-coding is acceptable, according to A server tests whether a content-coding is acceptable, according to
an Accept-Encoding field, using these rules: an Accept-Encoding field, using these rules:
1. If the content-coding is one of the content-codings listed in the 1. If the content-coding is one of the content-codings listed in the
Accept-Encoding field, then it is acceptable, unless it is Accept-Encoding field, then it is acceptable, unless it is
accompanied by a qvalue of 0. (As defined in Section 3.9, a accompanied by a qvalue of 0. (As defined in Section 3.9, a
qvalue of 0 means "not acceptable.") qvalue of 0 means "not acceptable.")
2. The special "*" symbol in an Accept-Encoding field matches any 2. The special "*" symbol in an Accept-Encoding field matches any
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associated with content-codings. This means that qvalues will not associated with content-codings. This means that qvalues will not
work and are not permitted with x-gzip or x-compress. work and are not permitted with x-gzip or x-compress.
14.4. Accept-Language 14.4. Accept-Language
The Accept-Language request-header field is similar to Accept, but The Accept-Language request-header field is similar to Accept, but
restricts the set of natural languages that are preferred as a restricts the set of natural languages that are preferred as a
response to the request. Language tags are defined in section response to the request. Language tags are defined in section
Section 3.10. Section 3.10.
Accept-Language = "Accept-Language" ":" Accept-Language = "Accept-Language" ":"
1#( language-range [ ";" "q" "=" qvalue ] ) 1#( language-range [ ";" "q" "=" qvalue ] )
language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" ) language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
Each language-range MAY be given an associated quality value which Each language-range MAY be given an associated quality value which
represents an estimate of the user's preference for the languages represents an estimate of the user's preference for the languages
specified by that range. The quality value defaults to "q=1". For specified by that range. The quality value defaults to "q=1". For
example, example,
Accept-Language: da, en-gb;q=0.8, en;q=0.7 Accept-Language: da, en-gb;q=0.8, en;q=0.7
would mean: "I prefer Danish, but will accept British English and would mean: "I prefer Danish, but will accept British English and
other types of English." A language-range matches a language-tag if other types of English." A language-range matches a language-tag if
it exactly equals the tag, or if it exactly equals a prefix of the it exactly equals the tag, or if it exactly equals a prefix of the
tag such that the first tag character following the prefix is "-". tag such that the first tag character following the prefix is "-".
The special range "*", if present in the Accept-Language field, The special range "*", if present in the Accept-Language field,
matches every tag not matched by any other range present in the matches every tag not matched by any other range present in the
Accept-Language field. Accept-Language field.
Note: This use of a prefix matching rule does not imply that Note: This use of a prefix matching rule does not imply that
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might assume that on selecting "en-gb", they will be served any might assume that on selecting "en-gb", they will be served any
kind of English document if British English is not available. A kind of English document if British English is not available. A
user agent might suggest in such a case to add "en" to get the user agent might suggest in such a case to add "en" to get the
best matching behavior. best matching behavior.
14.5. Accept-Ranges 14.5. Accept-Ranges
The Accept-Ranges response-header field allows the server to indicate The Accept-Ranges response-header field allows the server to indicate
its acceptance of range requests for a resource: its acceptance of range requests for a resource:
Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges
acceptable-ranges = 1#range-unit | "none" acceptable-ranges = 1#range-unit | "none"
Origin servers that accept byte-range requests MAY send Origin servers that accept byte-range requests MAY send
Accept-Ranges: bytes Accept-Ranges: bytes
but are not required to do so. Clients MAY generate byte-range but are not required to do so. Clients MAY generate byte-range
requests without having received this header for the resource requests without having received this header for the resource
involved. Range units are defined in Section 3.12. involved. Range units are defined in Section 3.12.
Servers that do not accept any kind of range request for a resource Servers that do not accept any kind of range request for a resource
MAY send MAY send
Accept-Ranges: none Accept-Ranges: none
to advise the client not to attempt a range request. to advise the client not to attempt a range request.
14.6. Age 14.6. Age
The Age response-header field conveys the sender's estimate of the The Age response-header field conveys the sender's estimate of the
amount of time since the response (or its revalidation) was generated amount of time since the response (or its revalidation) was generated
at the origin server. A cached response is "fresh" if its age does at the origin server. A cached response is "fresh" if its age does
not exceed its freshness lifetime. Age values are calculated as not exceed its freshness lifetime. Age values are calculated as
specified in Section 13.2.3. specified in Section 13.2.3.
Age = "Age" ":" age-value Age = "Age" ":" age-value
age-value = delta-seconds age-value = delta-seconds
Age values are non-negative decimal integers, representing time in Age values are non-negative decimal integers, representing time in
seconds. seconds.
If a cache receives a value larger than the largest positive integer If a cache receives a value larger than the largest positive integer
it can represent, or if any of its age calculations overflows, it it can represent, or if any of its age calculations overflows, it
MUST transmit an Age header with a value of 2147483648 (2^31). An MUST transmit an Age header with a value of 2147483648 (2^31). An
HTTP/1.1 server that includes a cache MUST include an Age header HTTP/1.1 server that includes a cache MUST include an Age header
field in every response generated from its own cache. Caches SHOULD field in every response generated from its own cache. Caches SHOULD
use an arithmetic type of at least 31 bits of range. use an arithmetic type of at least 31 bits of range.
14.7. Allow 14.7. Allow
The Allow entity-header field lists the set of methods supported by The Allow entity-header field lists the set of methods supported by
the resource identified by the Request-URI. The purpose of this the resource identified by the Request-URI. The purpose of this
field is strictly to inform the recipient of valid methods associated field is strictly to inform the recipient of valid methods associated
with the resource. An Allow header field MUST be present in a 405 with the resource. An Allow header field MUST be present in a 405
(Method Not Allowed) response. (Method Not Allowed) response.
Allow = "Allow" ":" #Method Allow = "Allow" ":" #Method
Example of use: Example of use:
Allow: GET, HEAD, PUT Allow: GET, HEAD, PUT
This field cannot prevent a client from trying other methods. This field cannot prevent a client from trying other methods.
However, the indications given by the Allow header field value SHOULD However, the indications given by the Allow header field value SHOULD
be followed. The actual set of allowed methods is defined by the be followed. The actual set of allowed methods is defined by the
origin server at the time of each request. origin server at the time of each request.
The Allow header field MAY be provided with a PUT request to The Allow header field MAY be provided with a PUT request to
recommend the methods to be supported by the new or modified recommend the methods to be supported by the new or modified
resource. The server is not required to support these methods and resource. The server is not required to support these methods and
SHOULD include an Allow header in the response giving the actual SHOULD include an Allow header in the response giving the actual
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14.8. Authorization 14.8. Authorization
A user agent that wishes to authenticate itself with a server-- A user agent that wishes to authenticate itself with a server--
usually, but not necessarily, after receiving a 401 response--does so usually, but not necessarily, after receiving a 401 response--does so
by including an Authorization request-header field with the request. by including an Authorization request-header field with the request.
The Authorization field value consists of credentials containing the The Authorization field value consists of credentials containing the
authentication information of the user agent for the realm of the authentication information of the user agent for the realm of the
resource being requested. resource being requested.
Authorization = "Authorization" ":" credentials Authorization = "Authorization" ":" credentials
HTTP access authentication is described in "HTTP Authentication: HTTP access authentication is described in "HTTP Authentication:
Basic and Digest Access Authentication" [43]. If a request is Basic and Digest Access Authentication" [43]. If a request is
authenticated and a realm specified, the same credentials SHOULD be authenticated and a realm specified, the same credentials SHOULD be
valid for all other requests within this realm (assuming that the valid for all other requests within this realm (assuming that the
authentication scheme itself does not require otherwise, such as authentication scheme itself does not require otherwise, such as
credentials that vary according to a challenge value or using credentials that vary according to a challenge value or using
synchronized clocks). synchronized clocks).
When a shared cache (see Section 13.7) receives a request containing When a shared cache (see Section 13.7) receives a request containing
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understand. understand.
For example, consider a hypothetical new response directive called For example, consider a hypothetical new response directive called
community which acts as a modifier to the private directive. We community which acts as a modifier to the private directive. We
define this new directive to mean that, in addition to any non-shared define this new directive to mean that, in addition to any non-shared
cache, any cache which is shared only by members of the community cache, any cache which is shared only by members of the community
named within its value may cache the response. An origin server named within its value may cache the response. An origin server
wishing to allow the UCI community to use an otherwise private wishing to allow the UCI community to use an otherwise private
response in their shared cache(s) could do so by including response in their shared cache(s) could do so by including
Cache-Control: private, community="UCI" Cache-Control: private, community="UCI"
A cache seeing this header field will act correctly even if the cache A cache seeing this header field will act correctly even if the cache
does not understand the community cache-extension, since it will also does not understand the community cache-extension, since it will also
see and understand the private directive and thus default to the safe see and understand the private directive and thus default to the safe
behavior. behavior.
Unrecognized cache-directives MUST be ignored; it is assumed that any Unrecognized cache-directives MUST be ignored; it is assumed that any
cache-directive likely to be unrecognized by an HTTP/1.1 cache will cache-directive likely to be unrecognized by an HTTP/1.1 cache will
be combined with standard directives (or the response's default be combined with standard directives (or the response's default
cacheability) such that the cache behavior will remain minimally cacheability) such that the cache behavior will remain minimally
correct even if the cache does not understand the extension(s). correct even if the cache does not understand the extension(s).
14.10. Connection 14.10. Connection
The Connection general-header field allows the sender to specify The Connection general-header field allows the sender to specify
options that are desired for that particular connection and MUST NOT options that are desired for that particular connection and MUST NOT
be communicated by proxies over further connections. be communicated by proxies over further connections.
The Connection header has the following grammar: The Connection header has the following grammar:
Connection = "Connection" ":" 1#(connection-token) Connection = "Connection" ":" 1#(connection-token)
connection-token = token connection-token = token
HTTP/1.1 proxies MUST parse the Connection header field before a HTTP/1.1 proxies MUST parse the Connection header field before a
message is forwarded and, for each connection-token in this field, message is forwarded and, for each connection-token in this field,
remove any header field(s) from the message with the same name as the remove any header field(s) from the message with the same name as the
connection-token. Connection options are signaled by the presence of connection-token. Connection options are signaled by the presence of
a connection-token in the Connection header field, not by any a connection-token in the Connection header field, not by any
corresponding additional header field(s), since the additional header corresponding additional header field(s), since the additional header
field may not be sent if there are no parameters associated with that field may not be sent if there are no parameters associated with that
connection option. connection option.
Message headers listed in the Connection header MUST NOT include end- Message headers listed in the Connection header MUST NOT include end-
to-end headers, such as Cache-Control. to-end headers, such as Cache-Control.
HTTP/1.1 defines the "close" connection option for the sender to HTTP/1.1 defines the "close" connection option for the sender to
signal that the connection will be closed after completion of the signal that the connection will be closed after completion of the
response. For example, response. For example,
Connection: close Connection: close
in either the request or the response header fields indicates that in either the request or the response header fields indicates that
the connection SHOULD NOT be considered `persistent' (Section 8.1) the connection SHOULD NOT be considered `persistent' (Section 8.1)
after the current request/response is complete. after the current request/response is complete.
HTTP/1.1 applications that do not support persistent connections MUST An HTTP/1.1 client that does not support persistent connections MUST
include the "close" connection option in every message. include the "close" connection option in every request message.
An HTTP/1.1 server that does not support persistent connections MUST
include the "close" connection option in every response message that
does not have a 1xx (informational) status code.
A system receiving an HTTP/1.0 (or lower-version) message that A system receiving an HTTP/1.0 (or lower-version) message that
includes a Connection header MUST, for each connection-token in this includes a Connection header MUST, for each connection-token in this
field, remove and ignore any header field(s) from the message with field, remove and ignore any header field(s) from the message with
the same name as the connection-token. This protects against the same name as the connection-token. This protects against
mistaken forwarding of such header fields by pre-HTTP/1.1 proxies. mistaken forwarding of such header fields by pre-HTTP/1.1 proxies.
See Appendix F.2. See Appendix F.2.
14.11. Content-Encoding 14.11. Content-Encoding
The Content-Encoding entity-header field is used as a modifier to the The Content-Encoding entity-header field is used as a modifier to the
media-type. When present, its value indicates what additional media-type. When present, its value indicates what additional
content codings have been applied to the entity-body, and thus what content codings have been applied to the entity-body, and thus what
decoding mechanisms must be applied in order to obtain the media-type decoding mechanisms must be applied in order to obtain the media-type
referenced by the Content-Type header field. Content-Encoding is referenced by the Content-Type header field. Content-Encoding is
primarily used to allow a document to be compressed without losing primarily used to allow a document to be compressed without losing
the identity of its underlying media type. the identity of its underlying media type.
Content-Encoding = "Content-Encoding" ":" 1#content-coding Content-Encoding = "Content-Encoding" ":" 1#content-coding
Content codings are defined in Section 3.5. An example of its use is Content codings are defined in Section 3.5. An example of its use is
Content-Encoding: gzip Content-Encoding: gzip
The content-coding is a characteristic of the entity identified by The content-coding is a characteristic of the entity identified by
the Request-URI. Typically, the entity-body is stored with this the Request-URI. Typically, the entity-body is stored with this
encoding and is only decoded before rendering or analogous usage. encoding and is only decoded before rendering or analogous usage.
However, a non-transparent proxy MAY modify the content-coding if the However, a non-transparent proxy MAY modify the content-coding if the
new coding is known to be acceptable to the recipient, unless the new coding is known to be acceptable to the recipient, unless the
"no-transform" cache-control directive is present in the message. "no-transform" cache-control directive is present in the message.
If the content-coding of an entity is not "identity", then the If the content-coding of an entity is not "identity", then the
response MUST include a Content-Encoding entity-header response MUST include a Content-Encoding entity-header
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Additional information about the encoding parameters MAY be provided Additional information about the encoding parameters MAY be provided
by other entity-header fields not defined by this specification. by other entity-header fields not defined by this specification.
14.12. Content-Language 14.12. Content-Language
The Content-Language entity-header field describes the natural The Content-Language entity-header field describes the natural
language(s) of the intended audience for the enclosed entity. Note language(s) of the intended audience for the enclosed entity. Note
that this might not be equivalent to all the languages used within that this might not be equivalent to all the languages used within
the entity-body. the entity-body.
Content-Language = "Content-Language" ":" 1#language-tag Content-Language = "Content-Language" ":" 1#language-tag
Language tags are defined in Section 3.10. The primary purpose of Language tags are defined in Section 3.10. The primary purpose of
Content-Language is to allow a user to identify and differentiate Content-Language is to allow a user to identify and differentiate
entities according to the user's own preferred language. Thus, if entities according to the user's own preferred language. Thus, if
the body content is intended only for a Danish-literate audience, the the body content is intended only for a Danish-literate audience, the
appropriate field is appropriate field is
Content-Language: da Content-Language: da
If no Content-Language is specified, the default is that the content If no Content-Language is specified, the default is that the content
is intended for all language audiences. This might mean that the is intended for all language audiences. This might mean that the
sender does not consider it to be specific to any natural language, sender does not consider it to be specific to any natural language,
or that the sender does not know for which language it is intended. or that the sender does not know for which language it is intended.
Multiple languages MAY be listed for content that is intended for Multiple languages MAY be listed for content that is intended for
multiple audiences. For example, a rendition of the "Treaty of multiple audiences. For example, a rendition of the "Treaty of
Waitangi," presented simultaneously in the original Maori and English Waitangi," presented simultaneously in the original Maori and English
versions, would call for versions, would call for
Content-Language: mi, en Content-Language: mi, en
However, just because multiple languages are present within an entity However, just because multiple languages are present within an entity
does not mean that it is intended for multiple linguistic audiences. does not mean that it is intended for multiple linguistic audiences.
An example would be a beginner's language primer, such as "A First An example would be a beginner's language primer, such as "A First
Lesson in Latin," which is clearly intended to be used by an English- Lesson in Latin," which is clearly intended to be used by an English-
literate audience. In this case, the Content-Language would properly literate audience. In this case, the Content-Language would properly
only include "en". only include "en".
Content-Language MAY be applied to any media type -- it is not Content-Language MAY be applied to any media type -- it is not
limited to textual documents. limited to textual documents.
14.13. Content-Length 14.13. Content-Length
The Content-Length entity-header field indicates the size of the The Content-Length entity-header field indicates the size of the
entity-body, in decimal number of OCTETs, sent to the recipient or, entity-body, in decimal number of OCTETs, sent to the recipient or,
in the case of the HEAD method, the size of the entity-body that in the case of the HEAD method, the size of the entity-body that
would have been sent had the request been a GET. would have been sent had the request been a GET.
Content-Length = "Content-Length" ":" 1*DIGIT Content-Length = "Content-Length" ":" 1*DIGIT
An example is An example is
Content-Length: 3495 Content-Length: 3495
Applications SHOULD use this field to indicate the transfer-length of Applications SHOULD use this field to indicate the transfer-length of
the message-body, unless this is prohibited by the rules in the message-body, unless this is prohibited by the rules in
Section 4.4. Section 4.4.
Any Content-Length greater than or equal to zero is a valid value. Any Content-Length greater than or equal to zero is a valid value.
Section 4.4 describes how to determine the length of a message-body Section 4.4 describes how to determine the length of a message-body
if a Content-Length is not given. if a Content-Length is not given.
Note that the meaning of this field is significantly different from Note that the meaning of this field is significantly different from
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The Content-Location entity-header field MAY be used to supply the The Content-Location entity-header field MAY be used to supply the
resource location for the entity enclosed in the message when that resource location for the entity enclosed in the message when that
entity is accessible from a location separate from the requested entity is accessible from a location separate from the requested
resource's URI. A server SHOULD provide a Content-Location for the resource's URI. A server SHOULD provide a Content-Location for the
variant corresponding to the response entity; especially in the case variant corresponding to the response entity; especially in the case
where a resource has multiple entities associated with it, and those where a resource has multiple entities associated with it, and those
entities actually have separate locations by which they might be entities actually have separate locations by which they might be
individually accessed, the server SHOULD provide a Content-Location individually accessed, the server SHOULD provide a Content-Location
for the particular variant which is returned. for the particular variant which is returned.
Content-Location = "Content-Location" ":" Content-Location = "Content-Location" ":"
( absoluteURI | relativeURI ) ( absoluteURI | relativeURI )
The value of Content-Location also defines the base URI for the The value of Content-Location also defines the base URI for the
entity. entity.
The Content-Location value is not a replacement for the original The Content-Location value is not a replacement for the original
requested URI; it is only a statement of the location of the resource requested URI; it is only a statement of the location of the resource
corresponding to this particular entity at the time of the request. corresponding to this particular entity at the time of the request.
Future requests MAY specify the Content-Location URI as the request- Future requests MAY specify the Content-Location URI as the request-
URI if the desire is to identify the source of that particular URI if the desire is to identify the source of that particular
entity. entity.
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undefined; servers are free to ignore it in those cases. undefined; servers are free to ignore it in those cases.
14.15. Content-MD5 14.15. Content-MD5
The Content-MD5 entity-header field, as defined in RFC 1864 [23], is The Content-MD5 entity-header field, as defined in RFC 1864 [23], is
an MD5 digest of the entity-body for the purpose of providing an end- an MD5 digest of the entity-body for the purpose of providing an end-
to-end message integrity check (MIC) of the entity-body. (Note: a to-end message integrity check (MIC) of the entity-body. (Note: a
MIC is good for detecting accidental modification of the entity-body MIC is good for detecting accidental modification of the entity-body
in transit, but is not proof against malicious attacks.) in transit, but is not proof against malicious attacks.)
Content-MD5 = "Content-MD5" ":" md5-digest Content-MD5 = "Content-MD5" ":" md5-digest
md5-digest = <base64 of 128 bit MD5 digest as per RFC 1864> md5-digest = <base64 of 128 bit MD5 digest as per RFC 1864>
The Content-MD5 header field MAY be generated by an origin server or The Content-MD5 header field MAY be generated by an origin server or
client to function as an integrity check of the entity-body. Only client to function as an integrity check of the entity-body. Only
origin servers or clients MAY generate the Content-MD5 header field; origin servers or clients MAY generate the Content-MD5 header field;
proxies and gateways MUST NOT generate it, as this would defeat its proxies and gateways MUST NOT generate it, as this would defeat its
value as an end-to-end integrity check. Any recipient of the entity- value as an end-to-end integrity check. Any recipient of the entity-
body, including gateways and proxies, MAY check that the digest value body, including gateways and proxies, MAY check that the digest value
in this header field matches that of the entity-body as received. in this header field matches that of the entity-body as received.
The MD5 digest is computed based on the content of the entity-body, The MD5 digest is computed based on the content of the entity-body,
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the digest is the transmission byte order defined for the type. the digest is the transmission byte order defined for the type.
Lastly, HTTP allows transmission of text types with any of several Lastly, HTTP allows transmission of text types with any of several
line break conventions and not just the canonical form using CRLF. line break conventions and not just the canonical form using CRLF.
14.16. Content-Range 14.16. Content-Range
The Content-Range entity-header is sent with a partial entity-body to The Content-Range entity-header is sent with a partial entity-body to
specify where in the full entity-body the partial body should be specify where in the full entity-body the partial body should be
applied. Range units are defined in Section 3.12. applied. Range units are defined in Section 3.12.
Content-Range = "Content-Range" ":" content-range-spec Content-Range = "Content-Range" ":" content-range-spec
content-range-spec = byte-content-range-spec content-range-spec = byte-content-range-spec
byte-content-range-spec = bytes-unit SP byte-content-range-spec = bytes-unit SP
byte-range-resp-spec "/" byte-range-resp-spec "/"
( instance-length | "*" ) ( instance-length | "*" )
byte-range-resp-spec = (first-byte-pos "-" last-byte-pos) byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
| "*" | "*"
instance-length = 1*DIGIT instance-length = 1*DIGIT
The header SHOULD indicate the total length of the full entity-body, The header SHOULD indicate the total length of the full entity-body,
unless this length is unknown or difficult to determine. The unless this length is unknown or difficult to determine. The
asterisk "*" character means that the instance-length is unknown at asterisk "*" character means that the instance-length is unknown at
the time when the response was generated. the time when the response was generated.
Unlike byte-ranges-specifier values (see Section 14.35.1), a byte- Unlike byte-ranges-specifier values (see Section 14.35.1), a byte-
range-resp-spec MUST only specify one range, and MUST contain range-resp-spec MUST only specify one range, and MUST contain
absolute byte positions for both the first and last byte of the absolute byte positions for both the first and last byte of the
range. range.
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A server sending a response with status code 416 (Requested range not A server sending a response with status code 416 (Requested range not
satisfiable) SHOULD include a Content-Range field with a byte-range- satisfiable) SHOULD include a Content-Range field with a byte-range-
resp-spec of "*". The instance-length specifies the current length resp-spec of "*". The instance-length specifies the current length
of the selected resource. A response with status code 206 (Partial of the selected resource. A response with status code 206 (Partial
Content) MUST NOT include a Content-Range field with a byte-range- Content) MUST NOT include a Content-Range field with a byte-range-
resp-spec of "*". resp-spec of "*".
Examples of byte-content-range-spec values, assuming that the entity Examples of byte-content-range-spec values, assuming that the entity
contains a total of 1234 bytes: contains a total of 1234 bytes:
. The first 500 bytes: . The first 500 bytes:
bytes 0-499/1234 bytes 0-499/1234
. The second 500 bytes: . The second 500 bytes:
bytes 500-999/1234 bytes 500-999/1234
. All except for the first 500 bytes: . All except for the first 500 bytes:
bytes 500-1233/1234 bytes 500-1233/1234
. The last 500 bytes: . The last 500 bytes:
bytes 734-1233/1234 bytes 734-1233/1234
When an HTTP message includes the content of a single range (for When an HTTP message includes the content of a single range (for
example, a response to a request for a single range, or to a request example, a response to a request for a single range, or to a request
for a set of ranges that overlap without any holes), this content is for a set of ranges that overlap without any holes), this content is
transmitted with a Content-Range header, and a Content-Length header transmitted with a Content-Range header, and a Content-Length header
showing the number of bytes actually transferred. For example, showing the number of bytes actually transferred. For example,
HTTP/1.1 206 Partial content HTTP/1.1 206 Partial content
Date: Wed, 15 Nov 1995 06:25:24 GMT Date: Wed, 15 Nov 1995 06:25:24 GMT
Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
Content-Range: bytes 21010-47021/47022 Content-Range: bytes 21010-47021/47022
Content-Length: 26012 Content-Length: 26012
Content-Type: image/gif Content-Type: image/gif
When an HTTP message includes the content of multiple ranges (for When an HTTP message includes the content of multiple ranges (for
example, a response to a request for multiple non-overlapping example, a response to a request for multiple non-overlapping
ranges), these are transmitted as a multipart message. The multipart ranges), these are transmitted as a multipart message. The multipart
media type used for this purpose is "multipart/byteranges" as defined media type used for this purpose is "multipart/byteranges" as defined
in Appendix B. See Appendix F.3 for a compatibility issue. in Appendix B. See Appendix F.3 for a compatibility issue.
A response to a request for a single range MUST NOT be sent using the A response to a request for a single range MUST NOT be sent using the
multipart/byteranges media type. A response to a request for multipart/byteranges media type. A response to a request for
multiple ranges, whose result is a single range, MAY be sent as a multiple ranges, whose result is a single range, MAY be sent as a
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range not satisfiable) response instead of a 200 (OK) response for range not satisfiable) response instead of a 200 (OK) response for
an unsatisfiable Range request-header, since not all servers an unsatisfiable Range request-header, since not all servers
implement this request-header. implement this request-header.
14.17. Content-Type 14.17. Content-Type
The Content-Type entity-header field indicates the media type of the The Content-Type entity-header field indicates the media type of the
entity-body sent to the recipient or, in the case of the HEAD method, entity-body sent to the recipient or, in the case of the HEAD method,
the media type that would have been sent had the request been a GET. the media type that would have been sent had the request been a GET.
Content-Type = "Content-Type" ":" media-type Content-Type = "Content-Type" ":" media-type
Media types are defined in Section 3.7. An example of the field is Media types are defined in Section 3.7. An example of the field is
Content-Type: text/html; charset=ISO-8859-4 Content-Type: text/html; charset=ISO-8859-4
Further discussion of methods for identifying the media type of an Further discussion of methods for identifying the media type of an
entity is provided in Section 7.2.1. entity is provided in Section 7.2.1.
14.18. Date 14.18. Date
The Date general-header field represents the date and time at which The Date general-header field represents the date and time at which
the message was originated, having the same semantics as orig-date in the message was originated, having the same semantics as orig-date in
RFC 822. The field value is an HTTP-date, as described in RFC 822. The field value is an HTTP-date, as described in
Section 3.3.1; it MUST be sent in RFC 1123 [8]-date format. Section 3.3.1; it MUST be sent in RFC 1123 [8]-date format.
Date = "Date" ":" HTTP-date Date = "Date" ":" HTTP-date
An example is An example is
Date: Tue, 15 Nov 1994 08:12:31 GMT Date: Tue, 15 Nov 1994 08:12:31 GMT
Origin servers MUST include a Date header field in all responses, Origin servers MUST include a Date header field in all responses,
except in these cases: except in these cases:
1. If the response status code is 100 (Continue) or 101 (Switching 1. If the response status code is 100 (Continue) or 101 (Switching
Protocols), the response MAY include a Date header field, at the Protocols), the response MAY include a Date header field, at the
server's option. server's option.
2. If the response status code conveys a server error, e.g. 500 2. If the response status code conveys a server error, e.g. 500
(Internal Server Error) or 503 (Service Unavailable), and it is (Internal Server Error) or 503 (Service Unavailable), and it is
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resource). resource).
14.19. ETag 14.19. ETag
The ETag response-header field provides the current value of the The ETag response-header field provides the current value of the
entity tag for the requested variant. The headers used with entity entity tag for the requested variant. The headers used with entity
tags are described in sections 14.24, 14.26 and 14.44. The entity tags are described in sections 14.24, 14.26 and 14.44. The entity
tag MAY be used for comparison with other entities from the same tag MAY be used for comparison with other entities from the same
resource (see Section 13.3.3). resource (see Section 13.3.3).
ETag = "ETag" ":" entity-tag ETag = "ETag" ":" entity-tag
Examples: Examples:
ETag: "xyzzy" ETag: "xyzzy"
ETag: W/"xyzzy" ETag: W/"xyzzy"
ETag: "" ETag: ""
14.20. Expect 14.20. Expect
The Expect request-header field is used to indicate that particular The Expect request-header field is used to indicate that particular
server behaviors are required by the client. server behaviors are required by the client.
Expect = "Expect" ":" 1#expectation Expect = "Expect" ":" 1#expectation
expectation = "100-continue" | expectation-extension expectation = "100-continue" | expectation-extension
expectation-extension = token [ "=" ( token | quoted-string ) expectation-extension = token [ "=" ( token | quoted-string )
*expect-params ] *expect-params ]
expect-params = ";" token [ "=" ( token | quoted-string ) ] expect-params = ";" token [ "=" ( token | quoted-string ) ]
A server that does not understand or is unable to comply with any of A server that does not understand or is unable to comply with any of
the expectation values in the Expect field of a request MUST respond the expectation values in the Expect field of a request MUST respond
with appropriate error status. The server MUST respond with a 417 with appropriate error status. The server MUST respond with a 417
(Expectation Failed) status if any of the expectations cannot be met (Expectation Failed) status if any of the expectations cannot be met
or, if there are other problems with the request, some other 4xx or, if there are other problems with the request, some other 4xx
status. status.
This header field is defined with extensible syntax to allow for This header field is defined with extensible syntax to allow for
future extensions. If a server receives a request containing an future extensions. If a server receives a request containing an
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intermediate cache that has a fresh copy of the entity). See intermediate cache that has a fresh copy of the entity). See
Section 13.2 for further discussion of the expiration model. Section 13.2 for further discussion of the expiration model.
The presence of an Expires field does not imply that the original The presence of an Expires field does not imply that the original
resource will change or cease to exist at, before, or after that resource will change or cease to exist at, before, or after that
time. time.
The format is an absolute date and time as defined by HTTP-date in The format is an absolute date and time as defined by HTTP-date in
Section 3.3.1; it MUST be in RFC 1123 date format: Section 3.3.1; it MUST be in RFC 1123 date format:
Expires = "Expires" ":" HTTP-date Expires = "Expires" ":" HTTP-date
An example of its use is An example of its use is
Expires: Thu, 01 Dec 1994 16:00:00 GMT Expires: Thu, 01 Dec 1994 16:00:00 GMT
Note: if a response includes a Cache-Control field with the max- Note: if a response includes a Cache-Control field with the max-
age directive (see Section 14.9.3), that directive overrides the age directive (see Section 14.9.3), that directive overrides the
Expires field. Expires field.
HTTP/1.1 clients and caches MUST treat other invalid date formats, HTTP/1.1 clients and caches MUST treat other invalid date formats,
especially including the value "0", as in the past (i.e., "already especially including the value "0", as in the past (i.e., "already
expired"). expired").
To mark a response as "already expired," an origin server sends an To mark a response as "already expired," an origin server sends an
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non-cacheable indicates that the response is cacheable, unless non-cacheable indicates that the response is cacheable, unless
indicated otherwise by a Cache-Control header field (Section 14.9). indicated otherwise by a Cache-Control header field (Section 14.9).
14.22. From 14.22. From
The From request-header field, if given, SHOULD contain an Internet The From request-header field, if given, SHOULD contain an Internet
e-mail address for the human user who controls the requesting user e-mail address for the human user who controls the requesting user
agent. The address SHOULD be machine-usable, as defined by "mailbox" agent. The address SHOULD be machine-usable, as defined by "mailbox"
in RFC 822 [9] as updated by RFC 1123 [8]: in RFC 822 [9] as updated by RFC 1123 [8]:
From = "From" ":" mailbox From = "From" ":" mailbox
An example is: An example is:
From: webmaster@w3.org From: webmaster@w3.org
This header field MAY be used for logging purposes and as a means for This header field MAY be used for logging purposes and as a means for
identifying the source of invalid or unwanted requests. It SHOULD identifying the source of invalid or unwanted requests. It SHOULD
NOT be used as an insecure form of access protection. The NOT be used as an insecure form of access protection. The
interpretation of this field is that the request is being performed interpretation of this field is that the request is being performed
on behalf of the person given, who accepts responsibility for the on behalf of the person given, who accepts responsibility for the
method performed. In particular, robot agents SHOULD include this method performed. In particular, robot agents SHOULD include this
header so that the person responsible for running the robot can be header so that the person responsible for running the robot can be
contacted if problems occur on the receiving end. contacted if problems occur on the receiving end.
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The Host request-header field specifies the Internet host and port The Host request-header field specifies the Internet host and port
number of the resource being requested, as obtained from the original number of the resource being requested, as obtained from the original
URI given by the user or referring resource (generally an HTTP URL, URI given by the user or referring resource (generally an HTTP URL,
as described in Section 3.2.2). The Host field value MUST represent as described in Section 3.2.2). The Host field value MUST represent
the naming authority of the origin server or gateway given by the the naming authority of the origin server or gateway given by the
original URL. This allows the origin server or gateway to original URL. This allows the origin server or gateway to
differentiate between internally-ambiguous URLs, such as the root "/" differentiate between internally-ambiguous URLs, such as the root "/"
URL of a server for multiple host names on a single IP address. URL of a server for multiple host names on a single IP address.
Host = "Host" ":" host [ ":" port ] ; Section 3.2.2 Host = "Host" ":" host [ ":" port ] ; Section 3.2.2
A "host" without any trailing port information implies the default A "host" without any trailing port information implies the default
port for the service requested (e.g., "80" for an HTTP URL). For port for the service requested (e.g., "80" for an HTTP URL). For
example, a request on the origin server for example, a request on the origin server for
<http://www.w3.org/pub/WWW/> would properly include: <http://www.example.org/pub/WWW/> would properly include:
GET /pub/WWW/ HTTP/1.1 GET /pub/WWW/ HTTP/1.1
Host: www.w3.org Host: www.example.org
A client MUST include a Host header field in all HTTP/1.1 request A client MUST include a Host header field in all HTTP/1.1 request
messages . If the requested URI does not include an Internet host messages . If the requested URI does not include an Internet host
name for the service being requested, then the Host header field MUST name for the service being requested, then the Host header field MUST
be given with an empty value. An HTTP/1.1 proxy MUST ensure that any be given with an empty value. An HTTP/1.1 proxy MUST ensure that any
request message it forwards does contain an appropriate Host header request message it forwards does contain an appropriate Host header
field that identifies the service being requested by the proxy. All field that identifies the service being requested by the proxy. All
Internet-based HTTP/1.1 servers MUST respond with a 400 (Bad Request) Internet-based HTTP/1.1 servers MUST respond with a 400 (Bad Request)
status code to any HTTP/1.1 request message which lacks a Host header status code to any HTTP/1.1 request message which lacks a Host header
field. field.
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conditional. A client that has one or more entities previously conditional. A client that has one or more entities previously
obtained from the resource can verify that one of those entities is obtained from the resource can verify that one of those entities is
current by including a list of their associated entity tags in the current by including a list of their associated entity tags in the
If-Match header field. Entity tags are defined in Section 3.11. The If-Match header field. Entity tags are defined in Section 3.11. The
purpose of this feature is to allow efficient updates of cached purpose of this feature is to allow efficient updates of cached
information with a minimum amount of transaction overhead. It is information with a minimum amount of transaction overhead. It is
also used, on updating requests, to prevent inadvertent modification also used, on updating requests, to prevent inadvertent modification
of the wrong version of a resource. As a special case, the value "*" of the wrong version of a resource. As a special case, the value "*"
matches any current entity of the resource. matches any current entity of the resource.
If-Match = "If-Match" ":" ( "*" | 1#entity-tag ) If-Match = "If-Match" ":" ( "*" | 1#entity-tag )
If any of the entity tags match the entity tag of the entity that If any of the entity tags match the entity tag of the entity that
would have been returned in the response to a similar GET request would have been returned in the response to a similar GET request
(without the If-Match header) on that resource, or if "*" is given (without the If-Match header) on that resource, or if "*" is given
and any current entity exists for that resource, then the server MAY and any current entity exists for that resource, then the server MAY
perform the requested method as if the If-Match header field did not perform the requested method as if the If-Match header field did not
exist. exist.
A server MUST use the strong comparison function (see Section 13.3.3) A server MUST use the strong comparison function (see Section 13.3.3)
to compare the entity tags in If-Match. to compare the entity tags in If-Match.
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MUST NOT be performed if the representation does not exist. MUST NOT be performed if the representation does not exist.
A request intended to update a resource (e.g., a PUT) MAY include an A request intended to update a resource (e.g., a PUT) MAY include an
If-Match header field to signal that the request method MUST NOT be If-Match header field to signal that the request method MUST NOT be
applied if the entity corresponding to the If-Match value (a single applied if the entity corresponding to the If-Match value (a single
entity tag) is no longer a representation of that resource. This entity tag) is no longer a representation of that resource. This
allows the user to indicate that they do not wish the request to be allows the user to indicate that they do not wish the request to be
successful if the resource has been changed without their knowledge. successful if the resource has been changed without their knowledge.
Examples: Examples:
If-Match: "xyzzy" If-Match: "xyzzy"
If-Match: "xyzzy", "r2d2xxxx", "c3piozzzz" If-Match: "xyzzy", "r2d2xxxx", "c3piozzzz"
If-Match: * If-Match: *
The result of a request having both an If-Match header field and The result of a request having both an If-Match header field and
either an If-None-Match or an If-Modified-Since header fields is either an If-None-Match or an If-Modified-Since header fields is
undefined by this specification. undefined by this specification.
14.25. If-Modified-Since 14.25. If-Modified-Since
The If-Modified-Since request-header field is used with a method to The If-Modified-Since request-header field is used with a method to
make it conditional: if the requested variant has not been modified make it conditional: if the requested variant has not been modified
since the time specified in this field, an entity will not be since the time specified in this field, an entity will not be
returned from the server; instead, a 304 (not modified) response will returned from the server; instead, a 304 (not modified) response will
be returned without any message-body. be returned without any message-body.
If-Modified-Since = "If-Modified-Since" ":" HTTP-date If-Modified-Since = "If-Modified-Since" ":" HTTP-date
An example of the field is: An example of the field is:
If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT
A GET method with an If-Modified-Since header and no Range header A GET method with an If-Modified-Since header and no Range header
requests that the identified entity be transferred only if it has requests that the identified entity be transferred only if it has
been modified since the date given by the If-Modified-Since header. been modified since the date given by the If-Modified-Since header.
The algorithm for determining this includes the following cases: The algorithm for determining this includes the following cases:
1. If the request would normally result in anything other than a 200 1. If the request would normally result in anything other than a 200
(OK) status, or if the passed If-Modified-Since date is invalid, (OK) status, or if the passed If-Modified-Since date is invalid,
the response is exactly the same as for a normal GET. A date the response is exactly the same as for a normal GET. A date
which is later than the server's current time is invalid. which is later than the server's current time is invalid.
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current by including a list of their associated entity tags in the current by including a list of their associated entity tags in the
If-None-Match header field. The purpose of this feature is to allow If-None-Match header field. The purpose of this feature is to allow
efficient updates of cached information with a minimum amount of efficient updates of cached information with a minimum amount of
transaction overhead. It is also used to prevent a method (e.g. transaction overhead. It is also used to prevent a method (e.g.
PUT) from inadvertently modifying an existing resource when the PUT) from inadvertently modifying an existing resource when the
client believes that the resource does not exist. client believes that the resource does not exist.
As a special case, the value "*" matches any current entity of the As a special case, the value "*" matches any current entity of the
resource. resource.
If-None-Match = "If-None-Match" ":" ( "*" | 1#entity-tag ) If-None-Match = "If-None-Match" ":" ( "*" | 1#entity-tag )
If any of the entity tags match the entity tag of the entity that If any of the entity tags match the entity tag of the entity that
would have been returned in the response to a similar GET request would have been returned in the response to a similar GET request
(without the If-None-Match header) on that resource, or if "*" is (without the If-None-Match header) on that resource, or if "*" is
given and any current entity exists for that resource, then the given and any current entity exists for that resource, then the
server MUST NOT perform the requested method, unless required to do server MUST NOT perform the requested method, unless required to do
so because the resource's modification date fails to match that so because the resource's modification date fails to match that
supplied in an If-Modified-Since header field in the request. supplied in an If-Modified-Since header field in the request.
Instead, if the request method was GET or HEAD, the server SHOULD Instead, if the request method was GET or HEAD, the server SHOULD
respond with a 304 (Not Modified) response, including the cache- respond with a 304 (Not Modified) response, including the cache-
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The meaning of "If-None-Match: *" is that the method MUST NOT be The meaning of "If-None-Match: *" is that the method MUST NOT be
performed if the representation selected by the origin server (or by performed if the representation selected by the origin server (or by
a cache, possibly using the Vary mechanism, see Section 14.44) a cache, possibly using the Vary mechanism, see Section 14.44)
exists, and SHOULD be performed if the representation does not exist. exists, and SHOULD be performed if the representation does not exist.
This feature is intended to be useful in preventing races between PUT This feature is intended to be useful in preventing races between PUT
operations. operations.
Examples: Examples:
If-None-Match: "xyzzy" If-None-Match: "xyzzy"
If-None-Match: W/"xyzzy" If-None-Match: W/"xyzzy"
If-None-Match: "xyzzy", "r2d2xxxx", "c3piozzzz" If-None-Match: "xyzzy", "r2d2xxxx", "c3piozzzz"
If-None-Match: W/"xyzzy", W/"r2d2xxxx", W/"c3piozzzz" If-None-Match: W/"xyzzy", W/"r2d2xxxx", W/"c3piozzzz"
If-None-Match: * If-None-Match: *
The result of a request having both an If-None-Match header field and The result of a request having both an If-None-Match header field and
either an If-Match or an If-Unmodified-Since header fields is either an If-Match or an If-Unmodified-Since header fields is
undefined by this specification. undefined by this specification.
14.27. If-Range 14.27. If-Range
If a client has a partial copy of an entity in its cache, and wishes If a client has a partial copy of an entity in its cache, and wishes
to have an up-to-date copy of the entire entity in its cache, it to have an up-to-date copy of the entire entity in its cache, it
could use the Range request-header with a conditional GET (using could use the Range request-header with a conditional GET (using
either or both of If-Unmodified-Since and If-Match.) However, if the either or both of If-Unmodified-Since and If-Match.) However, if the
condition fails because the entity has been modified, the client condition fails because the entity has been modified, the client
would then have to make a second request to obtain the entire current would then have to make a second request to obtain the entire current
entity-body. entity-body.
The If-Range header allows a client to "short-circuit" the second The If-Range header allows a client to "short-circuit" the second
request. Informally, its meaning is `if the entity is unchanged, request. Informally, its meaning is `if the entity is unchanged,
send me the part(s) that I am missing; otherwise, send me the entire send me the part(s) that I am missing; otherwise, send me the entire
new entity'. new entity'.
If-Range = "If-Range" ":" ( entity-tag | HTTP-date ) If-Range = "If-Range" ":" ( entity-tag | HTTP-date )
If the client has no entity tag for an entity, but does have a Last- If the client has no entity tag for an entity, but does have a Last-
Modified date, it MAY use that date in an If-Range header. (The Modified date, it MAY use that date in an If-Range header. (The
server can distinguish between a valid HTTP-date and any form of server can distinguish between a valid HTTP-date and any form of
entity-tag by examining no more than two characters.) The If-Range entity-tag by examining no more than two characters.) The If-Range
header SHOULD only be used together with a Range header, and MUST be header SHOULD only be used together with a Range header, and MUST be
ignored if the request does not include a Range header, or if the ignored if the request does not include a Range header, or if the
server does not support the sub-range operation. server does not support the sub-range operation.
If the entity tag given in the If-Range header matches the current If the entity tag given in the If-Range header matches the current
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The If-Unmodified-Since request-header field is used with a method to The If-Unmodified-Since request-header field is used with a method to
make it conditional. If the requested resource has not been modified make it conditional. If the requested resource has not been modified
since the time specified in this field, the server SHOULD perform the since the time specified in this field, the server SHOULD perform the
requested operation as if the If-Unmodified-Since header were not requested operation as if the If-Unmodified-Since header were not
present. present.
If the requested variant has been modified since the specified time, If the requested variant has been modified since the specified time,
the server MUST NOT perform the requested operation, and MUST return the server MUST NOT perform the requested operation, and MUST return
a 412 (Precondition Failed). a 412 (Precondition Failed).
If-Unmodified-Since = "If-Unmodified-Since" ":" HTTP-date If-Unmodified-Since = "If-Unmodified-Since" ":" HTTP-date
An example of the field is: An example of the field is:
If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT
If the request normally (i.e., without the If-Unmodified-Since If the request normally (i.e., without the If-Unmodified-Since
header) would result in anything other than a 2xx or 412 status, the header) would result in anything other than a 2xx or 412 status, the
If-Unmodified-Since header SHOULD be ignored. If-Unmodified-Since header SHOULD be ignored.
If the specified date is invalid, the header is ignored. If the specified date is invalid, the header is ignored.
The result of a request having both an If-Unmodified-Since header The result of a request having both an If-Unmodified-Since header
field and either an If-None-Match or an If-Modified-Since header field and either an If-None-Match or an If-Modified-Since header
fields is undefined by this specification. fields is undefined by this specification.
14.29. Last-Modified 14.29. Last-Modified
The Last-Modified entity-header field indicates the date and time at The Last-Modified entity-header field indicates the date and time at
which the origin server believes the variant was last modified. which the origin server believes the variant was last modified.
Last-Modified = "Last-Modified" ":" HTTP-date Last-Modified = "Last-Modified" ":" HTTP-date
An example of its use is An example of its use is
Last-Modified: Tue, 15 Nov 1994 12:45:26 GMT Last-Modified: Tue, 15 Nov 1994 12:45:26 GMT
The exact meaning of this header field depends on the implementation The exact meaning of this header field depends on the implementation
of the origin server and the nature of the original resource. For of the origin server and the nature of the original resource. For
files, it may be just the file system last-modified time. For files, it may be just the file system last-modified time. For
entities with dynamically included parts, it may be the most recent entities with dynamically included parts, it may be the most recent
of the set of last-modify times for its component parts. For of the set of last-modify times for its component parts. For
database gateways, it may be the last-update time stamp of the database gateways, it may be the last-update time stamp of the
record. For virtual objects, it may be the last time the internal record. For virtual objects, it may be the last time the internal
state changed. state changed.
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14.30. Location 14.30. Location
The Location response-header field is used to redirect the recipient The Location response-header field is used to redirect the recipient
to a location other than the Request-URI for completion of the to a location other than the Request-URI for completion of the
request or identification of a new resource. For 201 (Created) request or identification of a new resource. For 201 (Created)
responses, the Location is that of the new resource which was created responses, the Location is that of the new resource which was created
by the request. For 3xx responses, the location SHOULD indicate the by the request. For 3xx responses, the location SHOULD indicate the
server's preferred URI for automatic redirection to the resource. server's preferred URI for automatic redirection to the resource.
The field value consists of a single absolute URI. The field value consists of a single absolute URI.
Location = "Location" ":" absoluteURI Location = "Location" ":" absoluteURI [ "#" fragment ]
An example is: An example is:
Location: http://www.w3.org/pub/WWW/People.html Location: http://www.example.org/pub/WWW/People.html
Note: The Content-Location header field (Section 14.14) differs Note: The Content-Location header field (Section 14.14) differs
from Location in that the Content-Location identifies the original from Location in that the Content-Location identifies the original
location of the entity enclosed in the request. It is therefore location of the entity enclosed in the request. It is therefore
possible for a response to contain header fields for both Location possible for a response to contain header fields for both Location
and Content-Location. Also see Section 13.10 for cache and Content-Location. Also see Section 13.10 for cache
requirements of some methods. requirements of some methods.
There are circumstances in which a fragment identifier in a Location
URL would not be appropriate:
o With a 201 Created response, because in this usage the Location
header specifies the URL for the entire created resource.
o With a 300 Multiple Choices, since the choice decision is intended
to be made on resource characteristics and not fragment
characteristics.
o With 305 Use Proxy.
14.31. Max-Forwards 14.31. Max-Forwards
The Max-Forwards request-header field provides a mechanism with the The Max-Forwards request-header field provides a mechanism with the
TRACE (Section 9.8) and OPTIONS (Section 9.2) methods to limit the TRACE (Section 9.8) and OPTIONS (Section 9.2) methods to limit the
number of proxies or gateways that can forward the request to the number of proxies or gateways that can forward the request to the
next inbound server. This can be useful when the client is next inbound server. This can be useful when the client is
attempting to trace a request chain which appears to be failing or attempting to trace a request chain which appears to be failing or
looping in mid-chain. looping in mid-chain.
Max-Forwards = "Max-Forwards" ":" 1*DIGIT Max-Forwards = "Max-Forwards" ":" 1*DIGIT
The Max-Forwards value is a decimal integer indicating the remaining The Max-Forwards value is a decimal integer indicating the remaining
number of times this request message may be forwarded. number of times this request message may be forwarded.
Each proxy or gateway recipient of a TRACE or OPTIONS request Each proxy or gateway recipient of a TRACE or OPTIONS request
containing a Max-Forwards header field MUST check and update its containing a Max-Forwards header field MUST check and update its
value prior to forwarding the request. If the received value is zero value prior to forwarding the request. If the received value is zero
(0), the recipient MUST NOT forward the request; instead, it MUST (0), the recipient MUST NOT forward the request; instead, it MUST
respond as the final recipient. If the received Max-Forwards value respond as the final recipient. If the received Max-Forwards value
is greater than zero, then the forwarded message MUST contain an is greater than zero, then the forwarded message MUST contain an
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it is not explicitly referred to as part of that method definition. it is not explicitly referred to as part of that method definition.
14.32. Pragma 14.32. Pragma
The Pragma general-header field is used to include implementation- The Pragma general-header field is used to include implementation-
specific directives that might apply to any recipient along the specific directives that might apply to any recipient along the
request/response chain. All pragma directives specify optional request/response chain. All pragma directives specify optional
behavior from the viewpoint of the protocol; however, some systems behavior from the viewpoint of the protocol; however, some systems
MAY require that behavior be consistent with the directives. MAY require that behavior be consistent with the directives.
Pragma = "Pragma" ":" 1#pragma-directive Pragma = "Pragma" ":" 1#pragma-directive
pragma-directive = "no-cache" | extension-pragma pragma-directive = "no-cache" | extension-pragma
extension-pragma = token [ "=" ( token | quoted-string ) ] extension-pragma = token [ "=" ( token | quoted-string ) ]
When the no-cache directive is present in a request message, an When the no-cache directive is present in a request message, an
application SHOULD forward the request toward the origin server even application SHOULD forward the request toward the origin server even
if it has a cached copy of what is being requested. This pragma if it has a cached copy of what is being requested. This pragma
directive has the same semantics as the no-cache cache-directive (see directive has the same semantics as the no-cache cache-directive (see
Section 14.9) and is defined here for backward compatibility with Section 14.9) and is defined here for backward compatibility with
HTTP/1.0. Clients SHOULD include both header fields when a no-cache HTTP/1.0. Clients SHOULD include both header fields when a no-cache
request is sent to a server not known to be HTTP/1.1 compliant. request is sent to a server not known to be HTTP/1.1 compliant.
Pragma directives MUST be passed through by a proxy or gateway Pragma directives MUST be passed through by a proxy or gateway
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header field is not actually specified, it does not provide a header field is not actually specified, it does not provide a
reliable replacement for "Cache-Control: no-cache" in a response reliable replacement for "Cache-Control: no-cache" in a response
14.33. Proxy-Authenticate 14.33. Proxy-Authenticate
The Proxy-Authenticate response-header field MUST be included as part The Proxy-Authenticate response-header field MUST be included as part
of a 407 (Proxy Authentication Required) response. The field value of a 407 (Proxy Authentication Required) response. The field value
consists of a challenge that indicates the authentication scheme and consists of a challenge that indicates the authentication scheme and
parameters applicable to the proxy for this Request-URI. parameters applicable to the proxy for this Request-URI.
Proxy-Authenticate = "Proxy-Authenticate" ":" 1#challenge Proxy-Authenticate = "Proxy-Authenticate" ":" 1#challenge
The HTTP access authentication process is described in "HTTP The HTTP access authentication process is described in "HTTP
Authentication: Basic and Digest Access Authentication" [43]. Unlike Authentication: Basic and Digest Access Authentication" [43]. Unlike
WWW-Authenticate, the Proxy-Authenticate header field applies only to WWW-Authenticate, the Proxy-Authenticate header field applies only to
the current connection and SHOULD NOT be passed on to downstream the current connection and SHOULD NOT be passed on to downstream
clients. However, an intermediate proxy might need to obtain its own clients. However, an intermediate proxy might need to obtain its own
credentials by requesting them from the downstream client, which in credentials by requesting them from the downstream client, which in
some circumstances will appear as if the proxy is forwarding the some circumstances will appear as if the proxy is forwarding the
Proxy-Authenticate header field. Proxy-Authenticate header field.
14.34. Proxy-Authorization 14.34. Proxy-Authorization
The Proxy-Authorization request-header field allows the client to The Proxy-Authorization request-header field allows the client to
identify itself (or its user) to a proxy which requires identify itself (or its user) to a proxy which requires
authentication. The Proxy-Authorization field value consists of authentication. The Proxy-Authorization field value consists of
credentials containing the authentication information of the user credentials containing the authentication information of the user
agent for the proxy and/or realm of the resource being requested. agent for the proxy and/or realm of the resource being requested.
Proxy-Authorization = "Proxy-Authorization" ":" credentials Proxy-Authorization = "Proxy-Authorization" ":" credentials
The HTTP access authentication process is described in "HTTP The HTTP access authentication process is described in "HTTP
Authentication: Basic and Digest Access Authentication" [43]. Unlike Authentication: Basic and Digest Access Authentication" [43]. Unlike
Authorization, the Proxy-Authorization header field applies only to Authorization, the Proxy-Authorization header field applies only to
the next outbound proxy that demanded authentication using the Proxy- the next outbound proxy that demanded authentication using the Proxy-
Authenticate field. When multiple proxies are used in a chain, the Authenticate field. When multiple proxies are used in a chain, the
Proxy-Authorization header field is consumed by the first outbound Proxy-Authorization header field is consumed by the first outbound
proxy that was expecting to receive credentials. A proxy MAY relay proxy that was expecting to receive credentials. A proxy MAY relay
the credentials from the client request to the next proxy if that is the credentials from the client request to the next proxy if that is
the mechanism by which the proxies cooperatively authenticate a given the mechanism by which the proxies cooperatively authenticate a given
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of bytes, the concept of a byte range is meaningful for any HTTP of bytes, the concept of a byte range is meaningful for any HTTP
entity. (However, not all clients and servers need to support byte- entity. (However, not all clients and servers need to support byte-
range operations.) range operations.)
Byte range specifications in HTTP apply to the sequence of bytes in Byte range specifications in HTTP apply to the sequence of bytes in
the entity-body (not necessarily the same as the message-body). the entity-body (not necessarily the same as the message-body).
A byte range operation MAY specify a single range of bytes, or a set A byte range operation MAY specify a single range of bytes, or a set
of ranges within a single entity. of ranges within a single entity.
ranges-specifier = byte-ranges-specifier ranges-specifier = byte-ranges-specifier
byte-ranges-specifier = bytes-unit "=" byte-range-set byte-ranges-specifier = bytes-unit "=" byte-range-set
byte-range-set = 1#( byte-range-spec | suffix-byte-range-spec ) byte-range-set = 1#( byte-range-spec | suffix-byte-range-spec )
byte-range-spec = first-byte-pos "-" [last-byte-pos] byte-range-spec = first-byte-pos "-" [last-byte-pos]
first-byte-pos = 1*DIGIT first-byte-pos = 1*DIGIT
last-byte-pos = 1*DIGIT last-byte-pos = 1*DIGIT
The first-byte-pos value in a byte-range-spec gives the byte-offset The first-byte-pos value in a byte-range-spec gives the byte-offset
of the first byte in a range. The last-byte-pos value gives the of the first byte in a range. The last-byte-pos value gives the
byte-offset of the last byte in the range; that is, the byte byte-offset of the last byte in the range; that is, the byte
positions specified are inclusive. Byte offsets start at zero. positions specified are inclusive. Byte offsets start at zero.
If the last-byte-pos value is present, it MUST be greater than or If the last-byte-pos value is present, it MUST be greater than or
equal to the first-byte-pos in that byte-range-spec, or the byte- equal to the first-byte-pos in that byte-range-spec, or the byte-
range-spec is syntactically invalid. The recipient of a byte-range- range-spec is syntactically invalid. The recipient of a byte-range-
set that includes one or more syntactically invalid byte-range-spec set that includes one or more syntactically invalid byte-range-spec
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set. set.
If the last-byte-pos value is absent, or if the value is greater than If the last-byte-pos value is absent, or if the value is greater than
or equal to the current length of the entity-body, last-byte-pos is or equal to the current length of the entity-body, last-byte-pos is
taken to be equal to one less than the current length of the entity- taken to be equal to one less than the current length of the entity-
body in bytes. body in bytes.
By its choice of last-byte-pos, a client can limit the number of By its choice of last-byte-pos, a client can limit the number of
bytes retrieved without knowing the size of the entity. bytes retrieved without knowing the size of the entity.
suffix-byte-range-spec = "-" suffix-length suffix-byte-range-spec = "-" suffix-length
suffix-length = 1*DIGIT suffix-length = 1*DIGIT
A suffix-byte-range-spec is used to specify the suffix of the entity- A suffix-byte-range-spec is used to specify the suffix of the entity-
body, of a length given by the suffix-length value. (That is, this body, of a length given by the suffix-length value. (That is, this
form specifies the last N bytes of an entity-body.) If the entity is form specifies the last N bytes of an entity-body.) If the entity is
shorter than the specified suffix-length, the entire entity-body is shorter than the specified suffix-length, the entire entity-body is
used. used.
If a syntactically valid byte-range-set includes at least one byte- If a syntactically valid byte-range-set includes at least one byte-
range-spec whose first-byte-pos is less than the current length of range-spec whose first-byte-pos is less than the current length of
the entity-body, or at least one suffix-byte-range-spec with a non- the entity-body, or at least one suffix-byte-range-spec with a non-
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bytes=500-600,601-999 bytes=500-600,601-999
bytes=500-700,601-999 bytes=500-700,601-999
14.35.2. Range Retrieval Requests 14.35.2. Range Retrieval Requests
HTTP retrieval requests using conditional or unconditional GET HTTP retrieval requests using conditional or unconditional GET
methods MAY request one or more sub-ranges of the entity, instead of methods MAY request one or more sub-ranges of the entity, instead of
the entire entity, using the Range request header, which applies to the entire entity, using the Range request header, which applies to
the entity returned as the result of the request: the entity returned as the result of the request:
Range = "Range" ":" ranges-specifier Range = "Range" ":" ranges-specifier
A server MAY ignore the Range header. However, HTTP/1.1 origin A server MAY ignore the Range header. However, HTTP/1.1 origin
servers and intermediate caches ought to support byte ranges when servers and intermediate caches ought to support byte ranges when
possible, since Range supports efficient recovery from partially possible, since Range supports efficient recovery from partially
failed transfers, and supports efficient partial retrieval of large failed transfers, and supports efficient partial retrieval of large
entities. entities.
If the server supports the Range header and the specified range or If the server supports the Range header and the specified range or
ranges are appropriate for the entity: ranges are appropriate for the entity:
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The Referer[sic] request-header field allows the client to specify, The Referer[sic] request-header field allows the client to specify,
for the server's benefit, the address (URI) of the resource from for the server's benefit, the address (URI) of the resource from
which the Request-URI was obtained (the "referrer", although the which the Request-URI was obtained (the "referrer", although the
header field is misspelled.) The Referer request-header allows a header field is misspelled.) The Referer request-header allows a
server to generate lists of back-links to resources for interest, server to generate lists of back-links to resources for interest,
logging, optimized caching, etc. It also allows obsolete or mistyped logging, optimized caching, etc. It also allows obsolete or mistyped
links to be traced for maintenance. The Referer field MUST NOT be links to be traced for maintenance. The Referer field MUST NOT be
sent if the Request-URI was obtained from a source that does not have sent if the Request-URI was obtained from a source that does not have
its own URI, such as input from the user keyboard. its own URI, such as input from the user keyboard.
Referer = "Referer" ":" ( absoluteURI | relativeURI ) Referer = "Referer" ":" ( absoluteURI | relativeURI )
Example: Example:
Referer: http://www.w3.org/hypertext/DataSources/Overview.html Referer: http://www.example.org/hypertext/Overview.html
If the field value is a relative URI, it SHOULD be interpreted If the field value is a relative URI, it SHOULD be interpreted
relative to the Request-URI. The URI MUST NOT include a fragment. relative to the Request-URI. The URI MUST NOT include a fragment.
See Section 15.1.3 for security considerations. See Section 15.1.3 for security considerations.
14.37. Retry-After 14.37. Retry-After
The Retry-After response-header field can be used with a 503 (Service The Retry-After response-header field can be used with a 503 (Service
Unavailable) response to indicate how long the service is expected to Unavailable) response to indicate how long the service is expected to
be unavailable to the requesting client. This field MAY also be used be unavailable to the requesting client. This field MAY also be used
with any 3xx (Redirection) response to indicate the minimum time the with any 3xx (Redirection) response to indicate the minimum time the
user-agent is asked wait before issuing the redirected request. The user-agent is asked wait before issuing the redirected request. The
value of this field can be either an HTTP-date or an integer number value of this field can be either an HTTP-date or an integer number
of seconds (in decimal) after the time of the response. of seconds (in decimal) after the time of the response.
Retry-After = "Retry-After" ":" ( HTTP-date | delta-seconds ) Retry-After = "Retry-After" ":" ( HTTP-date | delta-seconds )
Two examples of its use are Two examples of its use are
Retry-After: Fri, 31 Dec 1999 23:59:59 GMT Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
Retry-After: 120 Retry-After: 120
In the latter example, the delay is 2 minutes. In the latter example, the delay is 2 minutes.
14.38. Server 14.38. Server
The Server response-header field contains information about the The Server response-header field contains information about the
software used by the origin server to handle the request. The field software used by the origin server to handle the request. The field
can contain multiple product tokens (Section 3.8) and comments can contain multiple product tokens (Section 3.8) and comments
identifying the server and any significant subproducts. The product identifying the server and any significant subproducts. The product
tokens are listed in order of their significance for identifying the tokens are listed in order of their significance for identifying the
application. application.
Server = "Server" ":" 1*( product | comment ) Server = "Server" ":" 1*( product | comment )
Example: Example:
Server: CERN/3.0 libwww/2.17 Server: CERN/3.0 libwww/2.17
If the response is being forwarded through a proxy, the proxy If the response is being forwarded through a proxy, the proxy
application MUST NOT modify the Server response-header. Instead, it application MUST NOT modify the Server response-header. Instead, it
SHOULD include a Via field (as described in Section 14.45). MUST include a Via field (as described in Section 14.45).
Note: Revealing the specific software version of the server might Note: Revealing the specific software version of the server might
allow the server machine to become more vulnerable to attacks allow the server machine to become more vulnerable to attacks
against software that is known to contain security holes. Server against software that is known to contain security holes. Server
implementors are encouraged to make this field a configurable implementors are encouraged to make this field a configurable
option. option.
14.39. TE 14.39. TE
The TE request-header field indicates what extension transfer-codings The TE request-header field indicates what extension transfer-codings
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t-codings = "trailers" | ( transfer-extension [ accept-params ] ) t-codings = "trailers" | ( transfer-extension [ accept-params ] )
The presence of the keyword "trailers" indicates that the client is The presence of the keyword "trailers" indicates that the client is
willing to accept trailer fields in a chunked transfer-coding, as willing to accept trailer fields in a chunked transfer-coding, as
defined in Section 3.6.1. This keyword is reserved for use with defined in Section 3.6.1. This keyword is reserved for use with
transfer-coding values even though it does not itself represent a transfer-coding values even though it does not itself represent a
transfer-coding. transfer-coding.
Examples of its use are: Examples of its use are:
TE: deflate TE: deflate
TE: TE:
TE: trailers, deflate;q=0.5 TE: trailers, deflate;q=0.5
The TE header field only applies to the immediate connection. The TE header field only applies to the immediate connection.
Therefore, the keyword MUST be supplied within a Connection header Therefore, the keyword MUST be supplied within a Connection header
field (Section 14.10) whenever TE is present in an HTTP/1.1 message. field (Section 14.10) whenever TE is present in an HTTP/1.1 message.
A server tests whether a transfer-coding is acceptable, according to A server tests whether a transfer-coding is acceptable, according to
a TE field, using these rules: a TE field, using these rules:
1. The "chunked" transfer-coding is always acceptable. If the 1. The "chunked" transfer-coding is always acceptable. If the
keyword "trailers" is listed, the client indicates that it is keyword "trailers" is listed, the client indicates that it is
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If the TE field-value is empty or if no TE field is present, the only If the TE field-value is empty or if no TE field is present, the only
transfer-coding is "chunked". A message with no transfer-coding is transfer-coding is "chunked". A message with no transfer-coding is
always acceptable. always acceptable.
14.40. Trailer 14.40. Trailer
The Trailer general field value indicates that the given set of The Trailer general field value indicates that the given set of
header fields is present in the trailer of a message encoded with header fields is present in the trailer of a message encoded with
chunked transfer-coding. chunked transfer-coding.
Trailer = "Trailer" ":" 1#field-name Trailer = "Trailer" ":" 1#field-name
An HTTP/1.1 message SHOULD include a Trailer header field in a An HTTP/1.1 message SHOULD include a Trailer header field in a
message using chunked transfer-coding with a non-empty trailer. message using chunked transfer-coding with a non-empty trailer.
Doing so allows the recipient to know which header fields to expect Doing so allows the recipient to know which header fields to expect
in the trailer. in the trailer.
If no Trailer header field is present, the trailer SHOULD NOT include If no Trailer header field is present, the trailer SHOULD NOT include
any header fields. See Section 3.6.1 for restrictions on the use of any header fields. See Section 3.6.1 for restrictions on the use of
trailer fields in a "chunked" transfer-coding. trailer fields in a "chunked" transfer-coding.
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o Trailer o Trailer
14.41. Transfer-Encoding 14.41. Transfer-Encoding
The Transfer-Encoding general-header field indicates what (if any) The Transfer-Encoding general-header field indicates what (if any)
type of transformation has been applied to the message body in order type of transformation has been applied to the message body in order
to safely transfer it between the sender and the recipient. This to safely transfer it between the sender and the recipient. This
differs from the content-coding in that the transfer-coding is a differs from the content-coding in that the transfer-coding is a
property of the message, not of the entity. property of the message, not of the entity.
Transfer-Encoding = "Transfer-Encoding" ":" 1#transfer-coding Transfer-Encoding = "Transfer-Encoding" ":" 1#transfer-coding
Transfer-codings are defined in Section 3.6. An example is: Transfer-codings are defined in Section 3.6. An example is:
Transfer-Encoding: chunked Transfer-Encoding: chunked
If multiple encodings have been applied to an entity, the transfer- If multiple encodings have been applied to an entity, the transfer-
codings MUST be listed in the order in which they were applied. codings MUST be listed in the order in which they were applied.
Additional information about the encoding parameters MAY be provided Additional information about the encoding parameters MAY be provided
by other entity-header fields not defined by this specification. by other entity-header fields not defined by this specification.
Many older HTTP/1.0 applications do not understand the Transfer- Many older HTTP/1.0 applications do not understand the Transfer-
Encoding header. Encoding header.
14.42. Upgrade 14.42. Upgrade
The Upgrade general-header allows the client to specify what The Upgrade general-header allows the client to specify what
additional communication protocols it supports and would like to use additional communication protocols it supports and would like to use
if the server finds it appropriate to switch protocols. The server if the server finds it appropriate to switch protocols. The server
MUST use the Upgrade header field within a 101 (Switching Protocols) MUST use the Upgrade header field within a 101 (Switching Protocols)
response to indicate which protocol(s) are being switched. response to indicate which protocol(s) are being switched.
Upgrade = "Upgrade" ":" 1#product Upgrade = "Upgrade" ":" 1#product
For example, For example,
Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11 Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
The Upgrade header field is intended to provide a simple mechanism The Upgrade header field is intended to provide a simple mechanism
for transition from HTTP/1.1 to some other, incompatible protocol. for transition from HTTP/1.1 to some other, incompatible protocol.
It does so by allowing the client to advertise its desire to use It does so by allowing the client to advertise its desire to use
another protocol, such as a later version of HTTP with a higher major another protocol, such as a later version of HTTP with a higher major
version number, even though the current request has been made using version number, even though the current request has been made using
HTTP/1.1. This eases the difficult transition between incompatible HTTP/1.1. This eases the difficult transition between incompatible
protocols by allowing the client to initiate a request in the more protocols by allowing the client to initiate a request in the more
commonly supported protocol while indicating to the server that it commonly supported protocol while indicating to the server that it
would like to use a "better" protocol if available (where "better" is would like to use a "better" protocol if available (where "better" is
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user agent originating the request. This is for statistical user agent originating the request. This is for statistical
purposes, the tracing of protocol violations, and automated purposes, the tracing of protocol violations, and automated
recognition of user agents for the sake of tailoring responses to recognition of user agents for the sake of tailoring responses to
avoid particular user agent limitations. User agents SHOULD include avoid particular user agent limitations. User agents SHOULD include
this field with requests. The field can contain multiple product this field with requests. The field can contain multiple product
tokens (Section 3.8) and comments identifying the agent and any tokens (Section 3.8) and comments identifying the agent and any
subproducts which form a significant part of the user agent. By subproducts which form a significant part of the user agent. By
convention, the product tokens are listed in order of their convention, the product tokens are listed in order of their
significance for identifying the application. significance for identifying the application.
User-Agent = "User-Agent" ":" 1*( product | comment ) User-Agent = "User-Agent" ":" 1*( product | comment )
Example: Example:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3 User-Agent: CERN-LineMode/2.15 libwww/2.17b3
14.44. Vary 14.44. Vary
The Vary field value indicates the set of request-header fields that The Vary field value indicates the set of request-header fields that
fully determines, while the response is fresh, whether a cache is fully determines, while the response is fresh, whether a cache is
permitted to use the response to reply to a subsequent request permitted to use the response to reply to a subsequent request
without revalidation. For uncacheable or stale responses, the Vary without revalidation. For uncacheable or stale responses, the Vary
field value advises the user agent about the criteria that were used field value advises the user agent about the criteria that were used
to select the representation. A Vary field value of "*" implies that to select the representation. A Vary field value of "*" implies that
a cache cannot determine from the request headers of a subsequent a cache cannot determine from the request headers of a subsequent
request whether this response is the appropriate representation. See request whether this response is the appropriate representation. See
Section 13.6 for use of the Vary header field by caches. Section 13.6 for use of the Vary header field by caches.
Vary = "Vary" ":" ( "*" | 1#field-name ) Vary = "Vary" ":" ( "*" | 1#field-name )
An HTTP/1.1 server SHOULD include a Vary header field with any An HTTP/1.1 server SHOULD include a Vary header field with any
cacheable response that is subject to server-driven negotiation. cacheable response that is subject to server-driven negotiation.
Doing so allows a cache to properly interpret future requests on that Doing so allows a cache to properly interpret future requests on that
resource and informs the user agent about the presence of negotiation resource and informs the user agent about the presence of negotiation
on that resource. A server MAY include a Vary header field with a on that resource. A server MAY include a Vary header field with a
non-cacheable response that is subject to server-driven negotiation, non-cacheable response that is subject to server-driven negotiation,
since this might provide the user agent with useful information about since this might provide the user agent with useful information about
the dimensions over which the response varies at the time of the the dimensions over which the response varies at the time of the
response. response.
A Vary field value consisting of a list of field-names signals that A Vary field value consisting of a list of field-names signals that
the representation selected for the response is based on a selection the representation selected for the response is based on a selection
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14.45. Via 14.45. Via
The Via general-header field MUST be used by gateways and proxies to The Via general-header field MUST be used by gateways and proxies to
indicate the intermediate protocols and recipients between the user indicate the intermediate protocols and recipients between the user
agent and the server on requests, and between the origin server and agent and the server on requests, and between the origin server and
the client on responses. It is analogous to the "Received" field of the client on responses. It is analogous to the "Received" field of
RFC 822 [9] and is intended to be used for tracking message forwards, RFC 822 [9] and is intended to be used for tracking message forwards,
avoiding request loops, and identifying the protocol capabilities of avoiding request loops, and identifying the protocol capabilities of
all senders along the request/response chain. all senders along the request/response chain.
Via = "Via" ":" 1#( received-protocol received-by [ comment ] ) Via = "Via" ":" 1#( received-protocol received-by [ comment ] )
received-protocol = [ protocol-name "/" ] protocol-version received-protocol = [ protocol-name "/" ] protocol-version
protocol-name = token protocol-name = token
protocol-version = token protocol-version = token
received-by = ( host [ ":" port ] ) | pseudonym received-by = ( host [ ":" port ] ) | pseudonym
pseudonym = token pseudonym = token
The received-protocol indicates the protocol version of the message The received-protocol indicates the protocol version of the message
received by the server or client along each segment of the request/ received by the server or client along each segment of the request/
response chain. The received-protocol version is appended to the Via response chain. The received-protocol version is appended to the Via
field value when the message is forwarded so that information about field value when the message is forwarded so that information about
the protocol capabilities of upstream applications remains visible to the protocol capabilities of upstream applications remains visible to
all recipients. all recipients.
The protocol-name is optional if and only if it would be "HTTP". The The protocol-name is optional if and only if it would be "HTTP". The
received-by field is normally the host and optional port number of a received-by field is normally the host and optional port number of a
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optional and MAY be removed by any recipient prior to forwarding the optional and MAY be removed by any recipient prior to forwarding the
message. message.
For example, a request message could be sent from an HTTP/1.0 user For example, a request message could be sent from an HTTP/1.0 user
agent to an internal proxy code-named "fred", which uses HTTP/1.1 to agent to an internal proxy code-named "fred", which uses HTTP/1.1 to
forward the request to a public proxy at nowhere.com, which completes forward the request to a public proxy at nowhere.com, which completes
the request by forwarding it to the origin server at www.ics.uci.edu. the request by forwarding it to the origin server at www.ics.uci.edu.
The request received by www.ics.uci.edu would then have the following The request received by www.ics.uci.edu would then have the following
Via header field: Via header field:
Via: 1.0 fred, 1.1 nowhere.com (Apache/1.1) Via: 1.0 fred, 1.1 nowhere.com (Apache/1.1)
Proxies and gateways used as a portal through a network firewall Proxies and gateways used as a portal through a network firewall
SHOULD NOT, by default, forward the names and ports of hosts within SHOULD NOT, by default, forward the names and ports of hosts within
the firewall region. This information SHOULD only be propagated if the firewall region. This information SHOULD only be propagated if
explicitly enabled. If not enabled, the received-by host of any host explicitly enabled. If not enabled, the received-by host of any host
behind the firewall SHOULD be replaced by an appropriate pseudonym behind the firewall SHOULD be replaced by an appropriate pseudonym
for that host. for that host.
For organizations that have strong privacy requirements for hiding For organizations that have strong privacy requirements for hiding
internal structures, a proxy MAY combine an ordered subsequence of internal structures, a proxy MAY combine an ordered subsequence of
Via header field entries with identical received-protocol values into Via header field entries with identical received-protocol values into
a single such entry. For example, a single such entry. For example,
Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
could be collapsed to could be collapsed to
Via: 1.0 ricky, 1.1 mertz, 1.0 lucy Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
Applications SHOULD NOT combine multiple entries unless they are all Applications SHOULD NOT combine multiple entries unless they are all
under the same organizational control and the hosts have already been under the same organizational control and the hosts have already been
replaced by pseudonyms. Applications MUST NOT combine entries which replaced by pseudonyms. Applications MUST NOT combine entries which
have different received-protocol values. have different received-protocol values.
14.46. Warning 14.46. Warning
The Warning general-header field is used to carry additional The Warning general-header field is used to carry additional
information about the status or transformation of a message which information about the status or transformation of a message which
might not be reflected in the message. This information is typically might not be reflected in the message. This information is typically
used to warn about a possible lack of semantic transparency from used to warn about a possible lack of semantic transparency from
caching operations or transformations applied to the entity body of caching operations or transformations applied to the entity body of
the message. the message.
Warning headers are sent with responses using: Warning headers are sent with responses using:
Warning = "Warning" ":" 1#warning-value Warning = "Warning" ":" 1#warning-value
warning-value = warn-code SP warn-agent SP warn-text warning-value = warn-code SP warn-agent SP warn-text
[SP warn-date] [SP warn-date]
warn-code = 3DIGIT warn-code = 3DIGIT
warn-agent = ( host [ ":" port ] ) | pseudonym warn-agent = ( host [ ":" port ] ) | pseudonym
; the name or pseudonym of the server adding ; the name or pseudonym of the server adding
; the Warning header, for use in debugging ; the Warning header, for use in debugging
warn-text = quoted-string warn-text = quoted-string
warn-date = <"> HTTP-date <"> warn-date = <"> HTTP-date <">
A response MAY carry more than one Warning header. A response MAY carry more than one Warning header.
The warn-text SHOULD be in a natural language and character set that The warn-text SHOULD be in a natural language and character set that
is most likely to be intelligible to the human user receiving the is most likely to be intelligible to the human user receiving the
response. This decision MAY be based on any available knowledge, response. This decision MAY be based on any available knowledge,
such as the location of the cache or user, the Accept-Language field such as the location of the cache or user, the Accept-Language field
in a request, the Content-Language field in a response, etc. The in a request, the Content-Language field in a response, etc. The
default language is English and the default character set is ISO- default language is English and the default character set is ISO-
8859-1. 8859-1.
skipping to change at page 159, line 43 skipping to change at page 162, line 14
of the warning-values are deleted for this reason, the Warning header of the warning-values are deleted for this reason, the Warning header
MUST be deleted as well. MUST be deleted as well.
14.47. WWW-Authenticate 14.47. WWW-Authenticate
The WWW-Authenticate response-header field MUST be included in 401 The WWW-Authenticate response-header field MUST be included in 401
(Unauthorized) response messages. The field value consists of at (Unauthorized) response messages. The field value consists of at
least one challenge that indicates the authentication scheme(s) and least one challenge that indicates the authentication scheme(s) and
parameters applicable to the Request-URI. parameters applicable to the Request-URI.
WWW-Authenticate = "WWW-Authenticate" ":" 1#challenge WWW-Authenticate = "WWW-Authenticate" ":" 1#challenge
The HTTP access authentication process is described in "HTTP The HTTP access authentication process is described in "HTTP
Authentication: Basic and Digest Access Authentication" [43]. User Authentication: Basic and Digest Access Authentication" [43]. User
agents are advised to take special care in parsing the WWW- agents are advised to take special care in parsing the WWW-
Authenticate field value as it might contain more than one challenge, Authenticate field value as it might contain more than one challenge,
or if more than one WWW-Authenticate header field is provided, the or if more than one WWW-Authenticate header field is provided, the
contents of a challenge itself can contain a comma-separated list of contents of a challenge itself can contain a comma-separated list of
authentication parameters. authentication parameters.
15. Security Considerations 15. Security Considerations
skipping to change at page 167, line 5 skipping to change at page 169, line 32
Groff, Phillip M. Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob Groff, Phillip M. Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob
McCool, Lou Montulli, Dave Raggett, Tony Sanders, and Marc McCool, Lou Montulli, Dave Raggett, Tony Sanders, and Marc
VanHeyningen deserve special recognition for their efforts in VanHeyningen deserve special recognition for their efforts in
defining early aspects of the protocol. defining early aspects of the protocol.
This document has benefited greatly from the comments of all those This document has benefited greatly from the comments of all those
participating in the HTTP-WG. In addition to those already participating in the HTTP-WG. In addition to those already
mentioned, the following individuals have contributed to this mentioned, the following individuals have contributed to this
specification: specification:
Gary Adams Ross Patterson Gary Adams, Harald Tveit Alvestrand, Keith Ball, Brian Behlendorf,
Harald Tveit Alvestrand Albert Lunde Paul Burchard, Maurizio Codogno, Mike Cowlishaw, Roman Czyborra,
Keith Ball John C. Mallery Michael A. Dolan, Daniel DuBois, David J. Fiander, Alan Freier, Marc
Brian Behlendorf Jean-Philippe Martin-Flatin Hedlund, Greg Herlihy, Koen Holtman, Alex Hopmann, Bob Jernigan, Shel
Paul Burchard Mitra Kaphan, Rohit Khare, John Klensin, Martijn Koster, Alexei Kosut,
Maurizio Codogno David Morris David M. Kristol, Daniel LaLiberte, Ben Laurie, Paul J. Leach, Albert
Mike Cowlishaw Gavin Nicol Lunde, John C. Mallery, Jean-Philippe Martin-Flatin, Mitra, David
Roman Czyborra Bill Perry Morris, Gavin Nicol, Ross Patterson, Bill Perry, Jeffrey Perry, Scott
Michael A. Dolan Jeffrey Perry Powers, Owen Rees, Luigi Rizzo, David Robinson, Marc Salomon, Rich
David J. Fiander Scott Powers Salz, Allan M. Schiffman, Jim Seidman, Chuck Shotton, Eric W. Sink,
Alan Freier Owen Rees Simon E. Spero, Richard N. Taylor, Robert S. Thau, Bill (BearHeart)
Marc Hedlund Luigi Rizzo Weinman, Francois Yergeau, Mary Ellen Zurko, Josh Cohen.
Greg Herlihy David Robinson
Koen Holtman Marc Salomon
Alex Hopmann Rich Salz
Bob Jernigan Allan M. Schiffman
Shel Kaphan Jim Seidman
Rohit Khare Chuck Shotton
John Klensin Eric W. Sink
Martijn Koster Simon E. Spero
Alexei Kosut Richard N. Taylor
David M. Kristol Robert S. Thau
Daniel LaLiberte Bill (BearHeart) Weinman
Ben Laurie Francois Yergeau
Paul J. Leach Mary Ellen Zurko
Daniel DuBois Josh Cohen
Much of the content and presentation of the caching design is due to Much of the content and presentation of the caching design is due to
suggestions and comments from individuals including: Shel Kaphan, suggestions and comments from individuals including: Shel Kaphan,
Paul Leach, Koen Holtman, David Morris, and Larry Masinter. Paul Leach, Koen Holtman, David Morris, and Larry Masinter.
Most of the specification of ranges is based on work originally done Most of the specification of ranges is based on work originally done
by Ari Luotonen and John Franks, with additional input from Steve by Ari Luotonen and John Franks, with additional input from Steve
Zilles. Zilles.
Thanks to the "cave men" of Palo Alto. You know who you are. Thanks to the "cave men" of Palo Alto. You know who you are.
Jim Gettys (the current editor of this document) wishes particularly Jim Gettys (the editor of [50]) wishes particularly to thank Roy
to thank Roy Fielding, the previous editor of this document, along Fielding, the editor of [33], along with John Klensin, Jeff Mogul,
with John Klensin, Jeff Mogul, Paul Leach, Dave Kristol, Koen Paul Leach, Dave Kristol, Koen Holtman, John Franks, Josh Cohen, Alex
Holtman, John Franks, Josh Cohen, Alex Hopmann, Scott Lawrence, and Hopmann, Scott Lawrence, and Larry Masinter for their help. And
Larry Masinter for their help. And thanks go particularly to Jeff thanks go particularly to Jeff Mogul and Scott Lawrence for
Mogul and Scott Lawrence for performing the "MUST/MAY/SHOULD" audit. performing the "MUST/MAY/SHOULD" audit.
The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik
Frystyk implemented RFC 2068 early, and we wish to thank them for the Frystyk implemented RFC 2068 early, and we wish to thank them for the
discovery of many of the problems that this document attempts to discovery of many of the problems that this document attempts to
rectify. rectify.
16.2. (This Document) 16.2. (This Document)
This document is based on [50], which was authored by Roy T. This document has benefited greatly from the comments of all those
Fielding, James Gettys, Jeffrey C. Mogul, Henrik Frystyk Nielsen, participating in the HTTP-WG. In particular, we thank Scott Lawrence
Larry Masinter, Paul J. Leach and Tim Berners-Lee. for maintaining the RFC2616 Errata list, and Roy Fielding, Bjoern
Hoehrmann, Larry Masinter, Howard Melman, Jeff Mogul and Alex
Rousskov for contributions to it.
17. References 17. References
17.1. References 17.1. References
[1] Alvestrand, H., "Tags for the Identification of Languages", [1] Alvestrand, H., "Tags for the Identification of Languages",
RFC 1766, March 1995. RFC 1766, March 1995.
[2] Anklesaria, F., McCahill, M., Lindner, P., Johnson, D., Torrey, [2] Anklesaria, F., McCahill, M., Lindner, P., Johnson, D., Torrey,
D., and B. Alberti, "The Internet Gopher Protocol (a D., and B. Alberti, "The Internet Gopher Protocol (a
skipping to change at page 172, line 35 skipping to change at page 174, line 35
Basic and Digest Access Authentication", RFC 2617, June 1999. Basic and Digest Access Authentication", RFC 2617, June 1999.
[44] Luotonen, A., "Tunneling TCP based protocols through Web proxy [44] Luotonen, A., "Tunneling TCP based protocols through Web proxy
servers", Work in Progress. servers", Work in Progress.
[45] Palme, J. and A. Hopmann, "MIME E-mail Encapsulation of [45] Palme, J. and A. Hopmann, "MIME E-mail Encapsulation of
Aggregate Documents, such as HTML (MHTML)", RFC 2110, Aggregate Documents, such as HTML (MHTML)", RFC 2110,
March 1997. March 1997.
[46] Bradner, S., "The Internet Standards Process -- Revision 3", [46] Bradner, S., "The Internet Standards Process -- Revision 3",
October 1996. BCP 9, RFC 2026, October 1996.
[47] Masinter, L., "Hyper Text Coffee Pot Control Protocol [47] Masinter, L., "Hyper Text Coffee Pot Control Protocol
(HTCPCP/1.0)", RFC 2324, April 1998. (HTCPCP/1.0)", RFC 2324, April 1998.
[48] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [48] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and Extensions (MIME) Part Five: Conformance Criteria and
Examples", RFC 2049, November 1996. Examples", RFC 2049, November 1996.
[49] Troost, R., Dorner, S., and K. Moore, "Communicating [49] Troost, R., Dorner, S., and K. Moore, "Communicating
Presentation Information in Internet Messages: The Content- Presentation Information in Internet Messages: The Content-
Disposition Header Field", RFC 2183, August 1997. Disposition Header Field", RFC 2183, August 1997.
17.2. Normative References 17.2. Informative References
[50] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., [50] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999. HTTP/1.1", RFC 2616, June 1999.
URIs URIs
[51] <mailto:ietf-http-wg@w3.org> [51] <mailto:ietf-http-wg@w3.org>
[52] <mailto:ietf-http-wg-request@w3.org?subject=subscribe> [52] <mailto:ietf-http-wg-request@w3.org?subject=subscribe>
skipping to change at page 179, line 35 skipping to change at page 181, line 35
D.1. MIME-Version D.1. MIME-Version
HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages
MAY include a single MIME-Version general-header field to indicate MAY include a single MIME-Version general-header field to indicate
what version of the MIME protocol was used to construct the message. what version of the MIME protocol was used to construct the message.
Use of the MIME-Version header field indicates that the message is in Use of the MIME-Version header field indicates that the message is in
full compliance with the MIME protocol (as defined in RFC 2045[7]). full compliance with the MIME protocol (as defined in RFC 2045[7]).
Proxies/gateways are responsible for ensuring full compliance (where Proxies/gateways are responsible for ensuring full compliance (where
possible) when exporting HTTP messages to strict MIME environments. possible) when exporting HTTP messages to strict MIME environments.
MIME-Version = "MIME-Version" ":" 1*DIGIT "." 1*DIGIT MIME-Version = "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
MIME version "1.0" is the default for use in HTTP/1.1. However, MIME version "1.0" is the default for use in HTTP/1.1. However,
HTTP/1.1 message parsing and semantics are defined by this document HTTP/1.1 message parsing and semantics are defined by this document
and not the MIME specification. and not the MIME specification.
D.2. Conversion to Canonical Form D.2. Conversion to Canonical Form
RFC 2045 [7] requires that an Internet mail entity be converted to RFC 2045 [7] requires that an Internet mail entity be converted to
canonical form prior to being transferred, as described in section 4 canonical form prior to being transferred, as described in section 4
of RFC 2049 [48]. Section 3.7.1 of this document describes the forms of RFC 2049 [48]. Section 3.7.1 of this document describes the forms
skipping to change at page 180, line 43 skipping to change at page 182, line 43
field or decode the entity-body before forwarding the message. (Some field or decode the entity-body before forwarding the message. (Some
experimental applications of Content-Type for Internet mail have used experimental applications of Content-Type for Internet mail have used
a media-type parameter of ";conversions=<content-coding>" to perform a media-type parameter of ";conversions=<content-coding>" to perform
a function equivalent to Content-Encoding. However, this parameter a function equivalent to Content-Encoding. However, this parameter
is not part of RFC 2045). is not part of RFC 2045).
D.5. No Content-Transfer-Encoding D.5. No Content-Transfer-Encoding
HTTP does not use the Content-Transfer-Encoding (CTE) field of RFC HTTP does not use the Content-Transfer-Encoding (CTE) field of RFC
2045. Proxies and gateways from MIME-compliant protocols to HTTP 2045. Proxies and gateways from MIME-compliant protocols to HTTP
MUST remove any non-identity CTE ("quoted-printable" or "base64") MUST remove any CTE encoding prior to delivering the response message
encoding prior to delivering the response message to an HTTP client. to an HTTP client.
Proxies and gateways from HTTP to MIME-compliant protocols are Proxies and gateways from HTTP to MIME-compliant protocols are
responsible for ensuring that the message is in the correct format responsible for ensuring that the message is in the correct format
and encoding for safe transport on that protocol, where "safe and encoding for safe transport on that protocol, where "safe
transport" is defined by the limitations of the protocol being used. transport" is defined by the limitations of the protocol being used.
Such a proxy or gateway SHOULD label the data with an appropriate Such a proxy or gateway SHOULD label the data with an appropriate
Content-Transfer-Encoding if doing so will improve the likelihood of Content-Transfer-Encoding if doing so will improve the likelihood of
safe transport over the destination protocol. safe transport over the destination protocol.
D.6. Introduction of Transfer-Encoding D.6. Introduction of Transfer-Encoding
HTTP/1.1 introduces the Transfer-Encoding header field HTTP/1.1 introduces the Transfer-Encoding header field
(Section 14.41). Proxies/gateways MUST remove any transfer-coding (Section 14.41). Proxies/gateways MUST remove any transfer-coding
prior to forwarding a message via a MIME-compliant protocol. prior to forwarding a message via a MIME-compliant protocol.
A process for decoding the "chunked" transfer-coding (Section 3.6) A process for decoding the "chunked" transfer-coding (Section 3.6)
can be represented in pseudo-code as: can be represented in pseudo-code as:
length := 0 length := 0
read chunk-size, chunk-extension (if any) and CRLF read chunk-size, chunk-extension (if any) and CRLF
while (chunk-size > 0) { while (chunk-size > 0) {
read chunk-data and CRLF read chunk-data and CRLF
append chunk-data to entity-body append chunk-data to entity-body
length := length + chunk-size length := length + chunk-size
read chunk-size and CRLF read chunk-size and CRLF
} }
read entity-header
while (entity-header not empty) {
append entity-header to existing header fields
read entity-header read entity-header
while (entity-header not empty) { }
append entity-header to existing header fields Content-Length := length
read entity-header Remove "chunked" from Transfer-Encoding
}
Content-Length := length
Remove "chunked" from Transfer-Encoding
D.7. MHTML and Line Length Limitations D.7. MHTML and Line Length Limitations
HTTP implementations which share code with MHTML [45] implementations HTTP implementations which share code with MHTML [45] implementations
need to be aware of MIME line length limitations. Since HTTP does need to be aware of MIME line length limitations. Since HTTP does
not have this limitation, HTTP does not fold long lines. MHTML not have this limitation, HTTP does not fold long lines. MHTML
messages being transported by HTTP follow all conventions of MHTML, messages being transported by HTTP follow all conventions of MHTML,
including line length limitations and folding, canonicalization, including line length limitations and folding, canonicalization,
etc., since HTTP transports all message-bodies as payload (see etc., since HTTP transports all message-bodies as payload (see
Section 3.7.2) and does not interpret the content or any MIME header Section 3.7.2) and does not interpret the content or any MIME header
skipping to change at page 182, line 36 skipping to change at page 184, line 36
content-disposition = "Content-Disposition" ":" content-disposition = "Content-Disposition" ":"
disposition-type *( ";" disposition-parm ) disposition-type *( ";" disposition-parm )
disposition-type = "attachment" | disp-extension-token disposition-type = "attachment" | disp-extension-token
disposition-parm = filename-parm | disp-extension-parm disposition-parm = filename-parm | disp-extension-parm
filename-parm = "filename" "=" quoted-string filename-parm = "filename" "=" quoted-string
disp-extension-token = token disp-extension-token = token
disp-extension-parm = token "=" ( token | quoted-string ) disp-extension-parm = token "=" ( token | quoted-string )
An example is An example is
Content-Disposition: attachment; filename="fname.ext" Content-Disposition: attachment; filename="fname.ext"
The receiving user agent SHOULD NOT respect any directory path The receiving user agent SHOULD NOT respect any directory path
information present in the filename-parm parameter, which is the only information present in the filename-parm parameter, which is the only
parameter believed to apply to HTTP implementations at this time. parameter believed to apply to HTTP implementations at this time.
The filename SHOULD be treated as a terminal component only. The filename SHOULD be treated as a terminal component only.
If this header is used in a response with the application/ If this header is used in a response with the application/
octet-stream content-type, the implied suggestion is that the user octet-stream content-type, the implied suggestion is that the user
agent should not display the response, but directly enter a `save agent should not display the response, but directly enter a `save
response as...' dialog. response as...' dialog.
skipping to change at page 183, line 33 skipping to change at page 185, line 33
o recognize the format of the Status-Line for HTTP/1.0 and 1.1 o recognize the format of the Status-Line for HTTP/1.0 and 1.1
responses; responses;
o understand any valid response in the format of HTTP/0.9, 1.0, or o understand any valid response in the format of HTTP/0.9, 1.0, or
1.1. 1.1.
For most implementations of HTTP/1.0, each connection is established For most implementations of HTTP/1.0, each connection is established
by the client prior to the request and closed by the server after by the client prior to the request and closed by the server after
sending the response. Some implementations implement the Keep-Alive sending the response. Some implementations implement the Keep-Alive
version of persistent connections described in section 19.7.1 of RFC version of persistent connections described in Section 19.7.1 of RFC
2068 [33]. 2068 [33].
F.1. Changes from HTTP/1.0 F.1. Changes from HTTP/1.0
This section summarizes major differences between versions HTTP/1.0 This section summarizes major differences between versions HTTP/1.0
and HTTP/1.1. and HTTP/1.1.
F.1.1. Changes to Simplify Multi-homed Web Servers and Conserve IP F.1.1. Changes to Simplify Multi-homed Web Servers and Conserve IP
Addresses Addresses
The requirements that clients and servers support the Host request- The requirements that clients and servers support the Host request-
header, report an error if the Host request-header (Section 14.23) is header, report an error if the Host request-header (Section 14.23) is
missing from an HTTP/1.1 request, and accept absolute URIs (section missing from an HTTP/1.1 request, and accept absolute URIs
5.1.2) are among the most important changes defined by this (Section 5.1.2) are among the most important changes defined by this
specification. specification.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for addresses and servers; there was no other established mechanism for
distinguishing the intended server of a request than the IP address distinguishing the intended server of a request than the IP address
to which that request was directed. The changes outlined above will to which that request was directed. The changes outlined above will
allow the Internet, once older HTTP clients are no longer common, to allow the Internet, once older HTTP clients are no longer common, to
support multiple Web sites from a single IP address, greatly support multiple Web sites from a single IP address, greatly
simplifying large operational Web servers, where allocation of many simplifying large operational Web servers, where allocation of many
IP addresses to a single host has created serious problems. The IP addresses to a single host has created serious problems. The
skipping to change at page 188, line 5 skipping to change at page 189, line 31
clients.(Section 3.6, 3.6.1, and 14.39) clients.(Section 3.6, 3.6.1, and 14.39)
The PATCH, LINK, UNLINK methods were defined but not commonly The PATCH, LINK, UNLINK methods were defined but not commonly
implemented in previous versions of this specification. See RFC 2068 implemented in previous versions of this specification. See RFC 2068
[33]. [33].
The Alternates, Content-Version, Derived-From, Link, URI, Public and The Alternates, Content-Version, Derived-From, Link, URI, Public and
Content-Base header fields were defined in previous versions of this Content-Base header fields were defined in previous versions of this
specification, but not commonly implemented. See RFC 2068 [33]. specification, but not commonly implemented. See RFC 2068 [33].
F.4. Changes from RFC 2616
Clarify that HTTP-Version is case sensitive. (Section 3.1)
Eliminate overlooked reference to "unsafe" characters.
(Section 3.2.3)
Clarify contexts that charset is used in. (Section 3.4)
Remove reference to non-existant identity transfer-coding value
tokens. (Sections 3.6, 4.4 and D.5)
Clarification that the chunk length does not include the count of the
octets in the chunk header and trailer. (Section 3.6.1)
Fix BNF to add query, as the abs_path production in Section 3 of [42]
doesn't define it. (Section 5.1.2)
Clarify definition of POST. (Section 9.5)
Clarify that it's not ok to use a weak cache validator in a 206
response. (Section 10.2.7)
Failed to consider that there are many other request methods that are
safe to automatically redirect, and further that the user agent is
able to make that determination based on the request method
semantics. (Sections 10.3.2, 10.3.3 and 10.3.8 )
Fix misspelled header. (Section 13.5.1)
Clarify denial of service attack avoidance requirement.
(Section 13.10)
Clarify exactly when close connection options must be sent.
(Section 14.10)
Correct syntax of Location header to allow fragment, as referred
symbol wasn't what was expected, and add some clarifications as to
when it would not be appropriate. (Section 14.30)
In the description of the Server header, the Via field was described
as a SHOULD. The requirement was and is stated correctly in the
description of the Via header, Section 14.45. (Section 14.38)
Appendix G. Change Log (to be removed by RFC Editor before publication) Appendix G. Change Log (to be removed by RFC Editor before publication)
G.1. Since RFC2616 G.1. Since RFC2616
Update Authors. Add Editorial Note and Acknowledgements (containing Update Authors. Add Editorial Note and Acknowledgements (containing
the original RFC2616 authors). Add "Normative References", the original RFC2616 authors). Add "Normative References",
containing just RFC2616 for now. containing just RFC2616 for now.
Appendix H. Open issues (to be removed by RFC Editor prior to G.2. Since draft-lafon-rfc2616bis-00
Add and resolve issues "charactersets", "chunk-size", "editor-notes",
"identity", "ifrange206", "invalidupd", "msg-len-chars",
"noclose1xx", "post", "saferedirect", "trailer-hop", "unsafe-uri",
"uriquery", "verscase" and "via-must" as proposed in
<http://purl.org/NET/http-errata>. Add and resolve issue "rfc2606-
compliance".
Add issues "languagetag", "media-reg" and "unneeded_references". Add
issue "location-fragments" and partly resolve it.
Reformat HTTP-WG contributors as a plain text paragraph.
Change [RFC2616] to be an informative reference. Fix RFC2026
reference (broken in draft 00). Outdent artwork to more closely
match RFC2616. (No change tracking for these changes).
Mark Yves Lafon and Julian Reschke as "Editor" in the front page and
the Authors section. Re-add all of the authors of RFC2616 for now.
(No change tracking for these changes).
Appendix H. Resolved issues (to be removed by RFC Editor before
publication) publication)
H.1. rfc2616bis Issues that were either rejected or resolved in this version of this
document.
H.1. rfc2606-compliance
Type: edit
julian.reschke@greenbytes.de (2006-10-19): Make sure that domain
names in examples use names reserved for that purpose (see RFC2606).
Resolution: Done.
H.2. editor-notes
Type: edit
<http://purl.org/NET/http-errata#editor-notes>
fielding@kiwi.ics.uci.edu (1999-08-03): See http://lists.w3.org/
Archives/Public/ietf-http-wg-old/1999MayAug/0102.html.
Resolution (2006-10-14): Not applicable. New References section is
generated by xml2rfc.
H.3. verscase
In Section 3.1:
Type: change
<http://purl.org/NET/http-errata#verscase>
fielding@apache.org (2002-09-16): See http://lists.w3.org/Archives/
Public/ietf-http-wg/2002JulSep/0066.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#verscase.
H.4. unsafe-uri
In Section 3.2.3:
Type: change
<http://purl.org/NET/http-errata#unsafe-uri>
fielding@kiwi.ICS.UCI.EDU (1999-09-10): See
http://ftp.ics.uci.edu/pub/ietf/http/hypermail/1999/0273.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#unsafe-uri.
H.5. charactersets
In Section 3.4:
Type: change
<http://purl.org/NET/http-errata#charactersets>
Howard@silverstream.com (2001-02-08): See http://lists.w3.org/
Archives/Public/ietf-http-wg-old/2001JanApr/0022.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#charactersets.
H.6. identity
In Section 3.6:
Type: change
<http://purl.org/NET/http-errata#identity>
LMM@acm.org (2001-11-05): See http://lists.w3.org/Archives/Public/
ietf-http-wg-old/2001SepDec/0018.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#identity.
H.7. chunk-size
In Section 3.6.1:
Type: change
<http://purl.org/NET/http-errata#chunk-size>
wham_bang@yahoo.com (1999-06-02): See http://lists.w3.org/Archives/
Public/ietf-http-wg-old/1999MayAug/0018.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#chunk-size.
H.8. msg-len-chars
In Section 4.4:
Type: edit
<http://purl.org/NET/http-errata#msg-len-chars>
fielding@kiwi.ics.uci.edu (1999-08-03): See http://lists.w3.org/
Archives/Public/ietf-http-wg-old/1999MayAug/0102.html.
Resolution (2006-10-13): Resolved as per
http://purl.org/NET/http-errata#msg-len-chars.
H.9. uriquery
In Section 5.1:
Type: change
<http://purl.org/NET/http-errata#uriquery>
LMM@acm.org (2001-07-30): See http://lists.w3.org/Archives/Public/
ietf-http-wg-old/2001MayAug/0034.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#uriquery.
H.10. post
In Section 9.5:
Type: change
<http://purl.org/NET/http-errata#post>
mogul@pa.dec.com (2002-04-09): See http://lists.w3.org/Archives/
Public/ietf-http-wg-old/2002JanApr/0024.html.
Resolution (2006-10-16): Resolved as per
http://purl.org/NET/http-errata#post.
H.11. ifrange206
In Section 10.2.7:
Type: change
<http://purl.org/NET/http-errata#identity>
rousskov@measurement-factory.com (2003-04-15): See http://
lists.w3.org/Archives/Public/ietf-http-wg/2003AprJun/0003.html.
Resolution (2006-10-16): Resolved as per
http://purl.org/NET/http-errata#ifrange206.
H.12. saferedirect
In Section 10.3.2:
Type: change
<http://purl.org/NET/http-errata#saferedirect>
fielding@ebuilt.com (2001-03-03): See http://lists.w3.org/Archives/
Public/ietf-http-wg-old/2001JanApr/0031.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#saferedirect.
H.13. trailer-hop
In Section 13.5.1:
Type: edit
<http://purl.org/NET/http-errata#trailer-hop>
mogul@pa.dec.com (2000-12-04): See http://lists.w3.org/Archives/
Public/ietf-http-wg-old/2000SepDec/0127.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#trailer-hop.
H.14. invalidupd
In Section 13.10:
Type: change
<http://purl.org/NET/http-errata#invalidupd>
Jeff.Mogul@hp.com (2002-06-21): See http://lists.w3.org/Archives/
Public/ietf-http-wg/2002AprJun/0058.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#invalidupd.
H.15. noclose1xx
In Section 14.10:
Type: change
<http://purl.org/NET/http-errata#noclose1xx>
fielding@ebuilt.com (2001-11-08): See http://lists.w3.org/Archives/
Public/ietf-http-wg-old/2001SepDec/0022.html.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#noclose1xx.
H.16. via-must
In Section 14.38:
Type: change
<http://purl.org/NET/http-errata#via-must>
julian.reschke@greenbytes.de (2006-10-14): See
http://purl.org/NET/http-errata#via-must.
Resolution (2006-10-14): Resolved as per
http://purl.org/NET/http-errata#via-must.
Appendix I. Open issues (to be removed by RFC Editor prior to
publication)
I.1. rfc2616bis
Type: edit Type: edit
julian.reschke@greenbytes.de (2006-10-10): Umbrella issue for changes julian.reschke@greenbytes.de (2006-10-10): Umbrella issue for changes
with respect to the revision process itself. with respect to the revision process itself.
H.2. edit I.2. unneeded_references
Type: edit Type: edit
julian.reschke@greenbytes.de (2006-08-10): Umbrella issue for <http://lists.w3.org/Archives/Public/ietf-http-wg/2006OctDec/
0054.html>
julian.reschke@greenbytes.de (2006-10-19): The reference entries for
RFC1866, RFC2069 and RFC2026 are unused. Remove them?
I.3. edit
Type: edit
julian.reschke@greenbytes.de (2006-10-08): Umbrella issue for
editorial fixes/enhancements. editorial fixes/enhancements.
I.4. media-reg
In Section 3.7:
Type: change
<http://purl.org/NET/http-errata#media-reg>
derhoermi@gmx.net (2000-09-10): See http://lists.w3.org/Archives/
Public/ietf-http-wg-old/2000SepDec/0013.html.
julian.reschke@greenbytes.de (2006-10-14): Resolve as part of general
update and reclassification of references.
I.5. languagetag
In Section 3:
Type: change
<http://purl.org/NET/http-errata#languagetag>
julian.reschke@greenbytes.de (2006-10-14): See
http://purl.org/NET/http-errata#languagetag.
julian.reschke@greenbytes.de (2006-10-14): In the meantime RFC3066
has been obsoleted by RFC4646. See also http://lists.w3.org/
Archives/Public/ietf-http-wg/2006OctDec/0001.html.
I.6. location-fragments
In Section 14.30:
Type: change
<http://purl.org/NET/http-errata#location-fragments>
fielding@kiwi.ics.uci.edu (1999-08-06): See http://lists.w3.org/
Archives/Public/ietf-http-wg-old/1999MayAug/0103.html.
julian.reschke@greenbytes.de (2006-10-16): Fix BNF and add note about
when it's appropriate to use fragments as suggested in
http://purl.org/NET/http-errata#location-fragments. This leaves us
with the open issue: _At present, the behavior in the case where
there was a fragment with the original URI, e.g.:
http://host1.example.com/resource1#fragment1 where /resource1
redirects to http://host2.example.com/resource2#fragment2 is
'fragment1' discarded? Do you find fragment2 and then find fragment1
within it? We don't have fragment combination rules._.
Index Index
1 1
100 Continue (status code) 65 100 Continue (status code) 67
101 Switching Protocols (status code) 65 101 Switching Protocols (status code) 67
2 2
200 OK (status code) 66 200 OK (status code) 68
201 Created (status code) 66 201 Created (status code) 68
202 Accepted (status code) 66 202 Accepted (status code) 68
203 Non-Authoritative Information (status code) 67 203 Non-Authoritative Information (status code) 69
204 No Content (status code) 67 204 No Content (status code) 69
205 Reset Content (status code) 67 205 Reset Content (status code) 69
206 Partial Content (status code) 68 206 Partial Content (status code) 70
3 3
300 Multiple Choices (status code) 69 300 Multiple Choices (status code) 71
301 Moved Permanently (status code) 69 301 Moved Permanently (status code) 71
302 Found (status code) 70 302 Found (status code) 72
303 See Other (status code) 70 303 See Other (status code) 72
304 Not Modified (status code) 71 304 Not Modified (status code) 73
305 Use Proxy (status code) 71 305 Use Proxy (status code) 73
306 (Unused) (status code) 72 306 (Unused) (status code) 74
307 Temporary Redirect (status code) 72 307 Temporary Redirect (status code) 74
4 4
400 Bad Request (status code) 73 400 Bad Request (status code) 75
401 Unauthorized (status code) 73 401 Unauthorized (status code) 75
402 Payment Required (status code) 73 402 Payment Required (status code) 75
403 Forbidden (status code) 73 403 Forbidden (status code) 75
404 Not Found (status code) 73 404 Not Found (status code) 75
405 Method Not Allowed (status code) 74 405 Method Not Allowed (status code) 76
406 Not Acceptable (status code) 74 406 Not Acceptable (status code) 76
407 Proxy Authentication Required (status code) 74 407 Proxy Authentication Required (status code) 76
408 Request Timeout (status code) 75 408 Request Timeout (status code) 77
409 Conflict (status code) 75 409 Conflict (status code) 77
410 Gone (status code) 75 410 Gone (status code) 77
411 Length Required (status code) 76 411 Length Required (status code) 78
412 Precondition Failed (status code) 76 412 Precondition Failed (status code) 78
413 Request Entity Too Large (status code) 76 413 Request Entity Too Large (status code) 78
414 Request-URI Too Long (status code) 76 414 Request-URI Too Long (status code) 78
415 Unsupported Media Type (status code) 76 415 Unsupported Media Type (status code) 78
416 Requested Range Not Satisfiable (status code) 76 416 Requested Range Not Satisfiable (status code) 78
417 Expectation Failed (status code) 77 417 Expectation Failed (status code) 79
5 5
500 Internal Server Error (status code) 77 500 Internal Server Error (status code) 79
501 Not Implemented (status code) 77 501 Not Implemented (status code) 79
502 Bad Gateway (status code) 77 502 Bad Gateway (status code) 79
503 Service Unavailable (status code) 78 503 Service Unavailable (status code) 80
504 Gateway Timeout (status code) 78 504 Gateway Timeout (status code) 80
505 HTTP Version Not Supported (status code) 78 505 HTTP Version Not Supported (status code) 80
A A
Accept header 109 Accept header 111
Accept-Charset header 111 Accept-Charset header 113
Accept-Encoding header 111 Accept-Encoding header 113
Accept-Language header 113 Accept-Language header 115
Accept-Ranges header 114 Accept-Ranges header 116
age 14 age 15
Age header 114 Age header 116
Allow header 115 Allow header 117
Authorization header 116 Authorization header 118
C C
cache 13 cache 14
Cache Directives Cache Directives
max-age 121, 123 max-age 123, 125
max-stale 121 max-stale 123
min-fresh 121 min-fresh 123
must-revalidate 123 must-revalidate 125
no-cache 119 no-cache 121
no-store 119 no-store 121
no-transform 125 no-transform 127
only-if-cached 123 only-if-cached 125
private 118 private 120
proxy-revalidate 124 proxy-revalidate 126
public 118 public 120
s-maxage 120 s-maxage 122
Cache-Control header 116 Cache-Control header 118
cacheable 13 cacheable 14
client 12 client 13
compress 27 compress 29
CONNECT method 64 CONNECT method 66
connection 11 connection 12
Connection header 126 Connection header 128
content negotiation 12 content negotiation 13
Content-Encoding header 127 Content-Encoding header 129
Content-Language header 128 Content-Language header 130
Content-Length header 128 Content-Length header 130
Content-Location header 129 Content-Location header 131
Content-MD5 header 130 Content-MD5 header 132
Content-Range header 131 Content-Range header 133
Content-Type header 133 Content-Type header 135
D D
Date header 133 Date header 136
deflate 28 deflate 29
DELETE method 63 DELETE method 65
downstream 15 downstream 16
E E
entity 11 entity 12
ETag header 135 ETag header 137
Expect header 135 Expect header 137
Expires header 136 Expires header 138
explicit expiration time 14 explicit expiration time 15
F F
first-hand 13 first-hand 14
fresh 14 fresh 15
freshness lifetime 14 freshness lifetime 15
From header 137 From header 139
G G
gateway 13 gateway 14
GET method 60 GET method 62
Grammar Grammar
Accept 109 Accept 111
Accept-Charset 111 Accept-Charset 113
Accept-Encoding 111 Accept-Encoding 113
accept-extension 109 accept-extension 111
Accept-Language 113 Accept-Language 115
accept-params 109 accept-params 111
Accept-Ranges 114 Accept-Ranges 116
acceptable-ranges 114 acceptable-ranges 116
Age 115 Age 117
age-value 115 age-value 117
Allow 115 Allow 117
ALPHA 20 ALPHA 21
asctime-date 25 asctime-date 27
attribute 28 attribute 30
Authorization 116 Authorization 118
byte-content-range-spec 131 byte-content-range-spec 133
byte-range-resp-spec 131 byte-range-resp-spec 133
byte-range-set 147 byte-range-set 149
byte-range-spec 147 byte-range-spec 149
byte-ranges-specifier 147 byte-ranges-specifier 149
bytes-unit 35 bytes-unit 36
Cache-Control 117 Cache-Control 119
cache-directive 117 cache-directive 119
cache-extension 117 cache-extension 119
cache-request-directive 117 cache-request-directive 119
cache-response-directive 117 cache-response-directive 119
CHAR 20 CHAR 21
charset 26 charset 28
chunk 30 chunk 31
chunk-data 30 chunk-data 31
chunk-ext-name 30 chunk-ext-name 31
chunk-ext-val 30 chunk-ext-val 31
chunk-extension 30 chunk-extension 31
chunk-size 30 chunk-size 31
Chunked-Body 30 Chunked-Body 31
codings 111 codings 113
comment 21 comment 22
Connection 126 Connection 128
connection-token 126 connection-token 128
content-coding 27 content-coding 29
content-disposition 182 content-disposition 184
Content-Encoding 127 Content-Encoding 129
Content-Language 128 Content-Language 130
Content-Length 128 Content-Length 131
Content-Location 129 Content-Location 131
Content-MD5 130 Content-MD5 132
Content-Range 131 Content-Range 133
content-range-spec 131 content-range-spec 133
Content-Type 133 Content-Type 135
CR 20 CR 21
CRLF 20 CRLF 21
ctext 21 ctext 22
CTL 20 CTL 21
Date 134 Date 136
date1 25 date1 27
date2 25 date2 27
date3 25 date3 27
delta-seconds 26 delta-seconds 27
DIGIT 20 DIGIT 21
disp-extension-parm 182 disp-extension-parm 184
disp-extension-token 182 disp-extension-token 184
disposition-parm 182 disposition-parm 184
disposition-type 182 disposition-type 184
entity-body 49 entity-body 51
entity-header 49 entity-header 51
entity-tag 34 entity-tag 36
ETag 135 ETag 137
Expect 135 Expect 137
expect-params 135 expect-params 137
expectation 135 expectation 137
expectation-extension 135 expectation-extension 137
Expires 136 Expires 138
extension-code 47 extension-code 49
extension-header 49 extension-header 51
extension-method 41 extension-method 43
extension-pragma 145 extension-pragma 148
field-content 37 field-content 39
field-name 37 field-name 39
field-value 37 field-value 39
filename-parm 182 filename-parm 184
first-byte-pos 147 first-byte-pos 149
From 137 From 139
general-header 40 general-header 42
generic-message 36 generic-message 38
HEX 21 HEX 22
Host 138 Host 140
HT 20 HT 21
HTTP-date 25 HTTP-date 27
HTTP-message 36 HTTP-message 38
HTTP-Version 22 HTTP-Version 23
http_URL 23 http_URL 25
If-Match 138 If-Match 140
If-Modified-Since 139 If-Modified-Since 142
If-None-Match 141 If-None-Match 143
If-Range 142 If-Range 144
If-Unmodified-Since 143 If-Unmodified-Since 145
instance-length 131 instance-length 133
language-range 113 language-range 115
language-tag 34 language-tag 35
last-byte-pos 147 last-byte-pos 149
last-chunk 30 last-chunk 31
Last-Modified 143 Last-Modified 145
LF 20 LF 21
LOALPHA 20 LOALPHA 21
Location 144 Location 146
LWS 20 LWS 21
Max-Forwards 145 Max-Forwards 147
md5-digest 130 md5-digest 132
media-range 109 media-range 111
media-type 31 media-type 32
message-body 37 message-body 39
message-header 37 message-header 39
Method 41 Method 43
MIME-Version 179 MIME-Version 181
month 25 month 27
OCTET 20 OCTET 21
opaque-tag 34 opaque-tag 36
other-range-unit 35 other-range-unit 36
parameter 28 parameter 30
Pragma 145 Pragma 148
pragma-directive 145 pragma-directive 148
primary-tag 34 primary-tag 35
product 33 product 34
product-version 33 product-version 34
protocol-name 155 protocol-name 158
protocol-version 155 protocol-version 158
Proxy-Authenticate 146 Proxy-Authenticate 148
Proxy-Authorization 146 Proxy-Authorization 149
pseudonym 155 pseudonym 158
qdtext 21 qdtext 22
quoted-pair 21 quoted-pair 22
quoted-string 21 quoted-string 22
qvalue 33 qvalue 35
Range 148 Range 151
range-unit 35 range-unit 36
ranges-specifier 147 ranges-specifier 149
Reason-Phrase 47 Reason-Phrase 49
received-by 155 received-by 158
received-protocol 155 received-protocol 158
Referer 149 Referer 152
Request 41 Request 43
request-header 44 request-header 46
Request-Line 41 Request-Line 43
Request-URI 42 Request-URI 44
Response 45 Response 47
response-header 48 response-header 50
Retry-After 150 Retry-After 152
rfc850-date 25 rfc850-date 27
rfc1123-date 25 rfc1123-date 27
separators 21 separators 22
Server 150 Server 153
SP 20 SP 21
start-line 36 start-line 38
Status-Code 47 Status-Code 49
Status-Line 45 Status-Line 47
subtag 34 subtag 35
subtype 31 subtype 32
suffix-byte-range-spec 147 suffix-byte-range-spec 150
suffix-length 147 suffix-length 150
t-codings 151 t-codings 153
TE 151 TE 153
TEXT 20 TEXT 21
time 25 time 27
token 21 token 22
Trailer 152 Trailer 154
trailer 30 trailer 31
transfer-coding 28 transfer-coding 30
Transfer-Encoding 152 Transfer-Encoding 155
transfer-extension 28 transfer-extension 30
type 31 type 32
UPALPHA 20 UPALPHA 21
Upgrade 153 Upgrade 155
User-Agent 154 User-Agent 156
value 28 value 30
Vary 154 Vary 157
Via 155 Via 158
warn-agent 157 warn-agent 159
warn-code 157 warn-code 159
warn-date 157 warn-date 159
warn-text 157 warn-text 159
Warning 157 Warning 159
warning-value 157 warning-value 159
weak 34 weak 36
weekday 25 weekday 27
wkday 25 wkday 27
WWW-Authenticate 159 WWW-Authenticate 162
gzip 27 gzip 29
H H
HEAD method 60 HEAD method 62
Headers Headers
Accept 109 Accept 111
Accept-Charset 111 Accept-Charset 113
Accept-Encoding 111 Accept-Encoding 113
Accept-Language 113 Accept-Language 115
Accept-Ranges 114 Accept-Ranges 116
Age 114 Age 116
Allow 115 Allow 117
Authorization 116 Authorization 118
Cache-Control 116 Cache-Control 118
Connection 126 Connection 128
Content-Encoding 127 Content-Encoding 129
Content-Language 128 Content-Language 130
Content-Length 128 Content-Length 130
Content-Location 129 Content-Location 131
Content-MD5 130 Content-MD5 132
Content-Range 131 Content-Range 133
Content-Type 133 Content-Type 135
Date 133 Date 136
ETag 135 ETag 137
Expect 135 Expect 137
Expires 136 Expires 138
From 137 From 139
Host 137 Host 140
If-Match 138 If-Match 140
If-Modified-Since 139 If-Modified-Since 141
If-None-Match 141 If-None-Match 143
If-Range 142 If-Range 144
If-Unmodified-Since 143 If-Unmodified-Since 145
Last-Modified 143 Last-Modified 145
Location 144 Location 146
Max-Forwards 144 Max-Forwards 147
Pragma 145 Pragma 147
Proxy-Authenticate 146 Proxy-Authenticate 148
Proxy-Authorization 146 Proxy-Authorization 149
Range 147 Range 149
Referer 149 Referer 152
Retry-After 150 Retry-After 152
Server 150 Server 152
TE 151 TE 153
Trailer 152 Trailer 154
Transfer-Encoding 152 Transfer-Encoding 155
Upgrade 153 Upgrade 155
User-Agent 154 User-Agent 156
Vary 154 Vary 157
Via 155 Via 157
Warning 157 Warning 159
WWW-Authenticate 159 WWW-Authenticate 162
heuristic expiration time 14 heuristic expiration time 15
Host header 137 Host header 140
I I
identity 28 identity 29
If-Match header 138 If-Match header 140
If-Modified-Since header 139 If-Modified-Since header 141
If-None-Match header 141 If-None-Match header 143
If-Range header 142 If-Range header 144
If-Unmodified-Since header 143 If-Unmodified-Since header 145
inbound 15 inbound 16
L L
Last-Modified header 143 Last-Modified header 145
Location header 144 Location header 146
M M
max-age max-age
Cache Directive 121, 123 Cache Directive 123, 125
Max-Forwards header 144 Max-Forwards header 147
max-stale max-stale
Cache Directive 121 Cache Directive 123
message 11 message 12
Methods Methods
CONNECT 64 CONNECT 66
DELETE 63 DELETE 65
GET 60 GET 62
HEAD 60 HEAD 62
OPTIONS 59 OPTIONS 61
POST 61 POST 63
PUT 62 PUT 64
TRACE 63 TRACE 65
min-fresh min-fresh
Cache Directive 121
must-revalidate
Cache Directive 123 Cache Directive 123
must-revalidate
Cache Directive 125
N N
no-cache no-cache
Cache Directive 119 Cache Directive 121
no-store no-store
Cache Directive 119 Cache Directive 121
no-transform no-transform
Cache Directive 125 Cache Directive 127
O O
only-if-cached only-if-cached
Cache Directive 123 Cache Directive 125
OPTIONS method 59 OPTIONS method 61
origin server 12 origin server 13
outbound 15 outbound 16
P P
POST method 61 POST method 63
Pragma header 145 Pragma header 147
private private
Cache Directive 118 Cache Directive 120
proxy 12 proxy 13
Proxy-Authenticate header 146 Proxy-Authenticate header 148
Proxy-Authorization header 146 Proxy-Authorization header 149
proxy-revalidate proxy-revalidate
Cache Directive 124 Cache Directive 126
public public
Cache Directive 118 Cache Directive 120
PUT method 62 PUT method 64
R R
Range header 147 Range header 149
Referer header 149 Referer header 152
representation 11 representation 12
request 11 request 12
resource 11 resource 12
response 11 response 12
Retry-After header 150 Retry-After header 152
S S
s-maxage s-maxage
Cache Directive 120 Cache Directive 122
semantically transparent 14 semantically transparent 15
server 12 server 13
Server header 150 Server header 152
stale 14 stale 15
Status Codes Status Codes
100 Continue 65 100 Continue 67
101 Switching Protocols 65 101 Switching Protocols 67
200 OK 66 200 OK 68
201 Created 66 201 Created 68
202 Accepted 66 202 Accepted 68
203 Non-Authoritative Information 67 203 Non-Authoritative Information 69
204 No Content 67 204 No Content 69
205 Reset Content 67 205 Reset Content 69
206 Partial Content 68 206 Partial Content 70
300 Multiple Choices 69 300 Multiple Choices 71
301 Moved Permanently 69 301 Moved Permanently 71
302 Found 70 302 Found 72
303 See Other 70 303 See Other 72
304 Not Modified 71 304 Not Modified 73
305 Use Proxy 71 305 Use Proxy 73
306 (Unused) 72 306 (Unused) 74
307 Temporary Redirect 72 307 Temporary Redirect 74
400 Bad Request 73 400 Bad Request 75
401 Unauthorized 73 401 Unauthorized 75
402 Payment Required 73 402 Payment Required 75
403 Forbidden 73 403 Forbidden 75
404 Not Found 73 404 Not Found 75
405 Method Not Allowed 74 405 Method Not Allowed 76
406 Not Acceptable 74 406 Not Acceptable 76
407 Proxy Authentication Required 74 407 Proxy Authentication Required 76
408 Request Timeout 75 408 Request Timeout 77
409 Conflict 75 409 Conflict 77
410 Gone 75 410 Gone 77
411 Length Required 76 411 Length Required 78
412 Precondition Failed 76 412 Precondition Failed 78
413 Request Entity Too Large 76 413 Request Entity Too Large 78
414 Request-URI Too Long 76 414 Request-URI Too Long 78
415 Unsupported Media Type 76 415 Unsupported Media Type 78
416 Requested Range Not Satisfiable 76 416 Requested Range Not Satisfiable 78
417 Expectation Failed 77 417 Expectation Failed 79
500 Internal Server Error 77 500 Internal Server Error 79
501 Not Implemented 77 501 Not Implemented 79
502 Bad Gateway 77 502 Bad Gateway 79
503 Service Unavailable 78 503 Service Unavailable 80
504 Gateway Timeout 78 504 Gateway Timeout 80
505 HTTP Version Not Supported 78 505 HTTP Version Not Supported 80
T T
TE header 151 TE header 153
TRACE method 63 TRACE method 65
Trailer header 152 Trailer header 154
Transfer-Encoding header 152 Transfer-Encoding header 155
tunnel 13 tunnel 14
U U
Upgrade header 153 Upgrade header 155
upstream 15 upstream 16
user agent 12 user agent 13
User-Agent header 154 User-Agent header 156
V V
validator 14 validator 15
variant 12 variant 13
Vary header 154 Vary header 157
Via header 155 Via header 157
W W
Warning header 157 Warning header 159
WWW-Authenticate header 159 WWW-Authenticate header 162
Authors' Addresses Authors' Addresses
Yves Lafon Roy T. Fielding
Day Software
23 Corporate Plaza DR, Suite 215
Newport Beach, CA 92660
USA
Phone: +1-949-706-5300
Fax: +1-949-706-5305
Email: fielding@gbiv.com
URI: http://roy.gbiv.com/
James Gettys
Hewlett-Packard Company
HP Labs, Cambridge Research Laboratory
One Cambridge Center
Cambridge, MA 02138
USA
Email: Jim.Gettys@hp.com
Jeffrey C. Mogul
Hewlett-Packard Company
HP Labs, Large Scale Systems Group
1501 Page Mill Road, MS 1177
Palo Alto, CA 94304
USA
Email: JeffMogul@acm.org
Henrik Frystyk Nielsen
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
Email: henrikn@microsoft.com
Larry Masinter
Adobe Systems, Incorporated
345 Park Ave
San Jose, CA 95110
USA
Email: LMM@acm.org
URI: http://larry.masinter.net/
Paul J. Leach
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
Email: paulle@microsoft.com
Tim Berners-Lee
World Wide Web Consortium
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139
USA
Fax: +1 (617) 258 8682
Email: timbl@w3.org
Yves Lafon (editor)
World Wide Web Consortium World Wide Web Consortium
2004, Route des Lucioles 2004, Route des Lucioles
Sophia Antipolis 06902 Sophia Antipolis 06902
France France
Phone: +33 492387943 Phone: +33 492387943
Fax: +33 492387822 Fax: +33 492387822
Email: ylafon@w3.org Email: ylafon@w3.org
URI: http://www.w3.org/ URI: http://www.w3.org/
Julian F. Reschke (editor)
Julian F. Reschke
greenbytes GmbH greenbytes GmbH
Hafenweg 16 Hafenweg 16
Muenster, NW 48155 Muenster, NW 48155
Germany Germany
Phone: +49 251 2807760 Phone: +49 251 2807760
Fax: +49 251 2807761 Fax: +49 251 2807761
Email: julian.reschke@greenbytes.de Email: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/ URI: http://greenbytes.de/tech/webdav/
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