rfc2616-orig.txt   draft-rfc2616bis-00.txt 
Network Working Group R. Fielding Network Working Group Y. Lafon
Request for Comments: 2616 UC Irvine Internet-Draft W3C
Obsoletes: 2068 J. Gettys Obsoletes: 2616 (if approved) J. Reschke
Category: Standards Track Compaq/W3C Intended status: Standards Track greenbytes
J. Mogul Expires: April 16, 2007 October 13, 2006
Compaq
H. Frystyk
W3C/MIT
L. Masinter
Xerox
P. Leach
Microsoft
T. Berners-Lee
W3C/MIT
June 1999
Hypertext Transfer Protocol -- HTTP/1.1 Hypertext Transfer Protocol -- HTTP/1.1
draft-lafon-rfc2616bis-00
Status of this Memo Status of this Memo
This document specifies an Internet standards track protocol for the By submitting this Internet-Draft, each author represents that any
Internet community, and requests discussion and suggestions for applicable patent or other IPR claims of which he or she is aware
improvements. Please refer to the current edition of the "Internet have been or will be disclosed, and any of which he or she becomes
Official Protocol Standards" (STD 1) for the standardization state aware will be disclosed, in accordance with Section 6 of BCP 79.
and status of this protocol. Distribution of this memo is unlimited.
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved. Copyright (C) The Internet Society (2006).
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
to be built independently of the data being transferred. to be built independently of the data being transferred.
HTTP has been in use by the World-Wide Web global information HTTP has been in use by the World-Wide Web global information
initiative since 1990. This specification defines the protocol initiative since 1990. This specification defines the protocol
referred to as "HTTP/1.1", and is an update to RFC 2068 [33]. referred to as "HTTP/1.1", and is an update to RFC2616.
Editorial Note (To be removed by RFC Editor before publication)
Distribution of this document is unlimited. Please send comments to
the Hypertext Transfer Protocol (HTTP) mailing list at
ietf-http-wg@w3.org [51], which may be joined by sending a message
with subject "subscribe" to ietf-http-wg-request@w3.org [52].
Discussions of the HTTP working group are archived at
<http://lists.w3.org/Archives/Public/ietf-http-wg/>. XML versions,
latest edits and the issues list for this document are available from
<http://www.w3.org/Protocols/HTTP/1.1/>.
The purpose of this document is to revise RFC2616 ([50]), doing only
minimal corrections. For now, it is not planned to advance the
standards level of HTTP, thus - if published - the specification will
still be a "Proposed Standard" (see [46]).
The current plan is to incorporate known errata, and to update the
specification text according to the current IETF publication
guidelines. In particular:
o Incorporate the corrections collected in the RFC2616 errata
document (<http://skrb.org/ietf/http_errata.html>) and potentially
newly discovered and agreed-upon errata.
o Update references, and re-classify them into "Normative" and
"Informative", based on the prior work done by Jim Gettys in
<http://tools.ietf.org/html/draft-gettys-http-v11-spec-rev-00>.
This document is based on a variant of the original RFC2616
specification formatted using Marshall T. Rose's "xml2rfc" tool (see
<http://xml.resource.org>) and therefore deviates from the original
text in word wrapping, page breaks, list formatting, reference
formatting, whitespace usage and appendix numbering. Otherwise, it
is supposed to contain an accurate copy of the original specification
text. See <http://www.w3.org/Protocols/HTTP/1.1/
rfc2616bis-00-from-rfc2616.diff.html> for a comparison between both
documents, as generated by "rfcdiff"
(<http://tools.ietf.org/tools/rfcdiff/>).
Table of Contents Table of Contents
1 Introduction ...................................................7 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 10
1.1 Purpose......................................................7 1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.2 Requirements .................................................8 1.2 Requirements . . . . . . . . . . . . . . . . . . . . . . 10
1.3 Terminology ..................................................8 1.3 Terminology . . . . . . . . . . . . . . . . . . . . . . . 11
1.4 Overall Operation ...........................................12 1.4 Overall Operation . . . . . . . . . . . . . . . . . . . . 15
2 Notational Conventions and Generic Grammar ....................14 2 Notational Conventions and Generic Grammar . . . . . . . . . 18
2.1 Augmented BNF ...............................................14 2.1 Augmented BNF . . . . . . . . . . . . . . . . . . . . . . 18
2.2 Basic Rules .................................................15 2.2 Basic Rules . . . . . . . . . . . . . . . . . . . . . . . 20
3 Protocol Parameters ...........................................17 3 Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 22
3.1 HTTP Version ................................................17 3.1 HTTP Version . . . . . . . . . . . . . . . . . . . . . . 22
3.2 Uniform Resource Identifiers ................................18 3.2 Uniform Resource Identifiers . . . . . . . . . . . . . . 23
3.2.1 General Syntax ...........................................19 3.2.1 General Syntax . . . . . . . . . . . . . . . . . . . 23
3.2.2 http URL .................................................19 3.2.2 http URL . . . . . . . . . . . . . . . . . . . . . . 23
3.2.3 URI Comparison ...........................................20 3.2.3 URI Comparison . . . . . . . . . . . . . . . . . . . 24
3.3 Date/Time Formats ...........................................20 3.3 Date/Time Formats . . . . . . . . . . . . . . . . . . . . 24
3.3.1 Full Date ................................................20 3.3.1 Full Date . . . . . . . . . . . . . . . . . . . . . . 24
3.3.2 Delta Seconds ............................................21 3.3.2 Delta Seconds . . . . . . . . . . . . . . . . . . . . 26
3.4 Character Sets ..............................................21 3.4 Character Sets . . . . . . . . . . . . . . . . . . . . . 26
3.4.1 Missing Charset ..........................................22 3.4.1 Missing Charset . . . . . . . . . . . . . . . . . . . 27
3.5 Content Codings .............................................23 3.5 Content Codings . . . . . . . . . . . . . . . . . . . . . 27
3.6 Transfer Codings ............................................24 3.6 Transfer Codings . . . . . . . . . . . . . . . . . . . . 28
3.6.1 Chunked Transfer Coding ..................................25 3.6.1 Chunked Transfer Coding . . . . . . . . . . . . . . . 29
3.7 Media Types .................................................26 3.7 Media Types . . . . . . . . . . . . . . . . . . . . . . . 31
3.7.1 Canonicalization and Text Defaults .......................27 3.7.1 Canonicalization and Text Defaults . . . . . . . . . 31
3.7.2 Multipart Types ..........................................27 3.7.2 Multipart Types . . . . . . . . . . . . . . . . . . . 32
3.8 Product Tokens ..............................................28 3.8 Product Tokens . . . . . . . . . . . . . . . . . . . . . 33
3.9 Quality Values ..............................................29 3.9 Quality Values . . . . . . . . . . . . . . . . . . . . . 33
3.10 Language Tags ...............................................29 3.10 Language Tags . . . . . . . . . . . . . . . . . . . . . . 34
3.11 Entity Tags .................................................30 3.11 Entity Tags . . . . . . . . . . . . . . . . . . . . . . . 34
3.12 Range Units .................................................30 3.12 Range Units . . . . . . . . . . . . . . . . . . . . . . . 35
4 HTTP Message ..................................................31 4 HTTP Message . . . . . . . . . . . . . . . . . . . . . . . . 36
4.1 Message Types ...............................................31 4.1 Message Types . . . . . . . . . . . . . . . . . . . . . . 36
4.2 Message Headers .............................................31 4.2 Message Headers . . . . . . . . . . . . . . . . . . . . . 36
4.3 Message Body ................................................32 4.3 Message Body . . . . . . . . . . . . . . . . . . . . . . 37
4.4 Message Length ..............................................33 4.4 Message Length . . . . . . . . . . . . . . . . . . . . . 38
4.5 General Header Fields .......................................34 4.5 General Header Fields . . . . . . . . . . . . . . . . . . 39
5 Request .......................................................35 5 Request . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.1 Request-Line ................................................35 5.1 Request-Line . . . . . . . . . . . . . . . . . . . . . . 41
5.1.1 Method ...................................................36 5.1.1 Method . . . . . . . . . . . . . . . . . . . . . . . 41
5.1.2 Request-URI ..............................................36 5.1.2 Request-URI . . . . . . . . . . . . . . . . . . . . . 42
5.2 The Resource Identified by a Request ........................38 5.2 The Resource Identified by a Request . . . . . . . . . . 43
5.3 Request Header Fields .......................................38 5.3 Request Header Fields . . . . . . . . . . . . . . . . . . 44
6 Response ......................................................39 6 Response . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.1 Status-Line .................................................39 6.1 Status-Line . . . . . . . . . . . . . . . . . . . . . . . 45
6.1.1 Status Code and Reason Phrase ............................39 6.1.1 Status Code and Reason Phrase . . . . . . . . . . . . 45
6.2 Response Header Fields ......................................41 6.2 Response Header Fields . . . . . . . . . . . . . . . . . 48
7 Entity ........................................................42 7 Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7.1 Entity Header Fields ........................................42 7.1 Entity Header Fields . . . . . . . . . . . . . . . . . . 49
7.2 Entity Body .................................................43 7.2 Entity Body . . . . . . . . . . . . . . . . . . . . . . . 49
7.2.1 Type .....................................................43 7.2.1 Type . . . . . . . . . . . . . . . . . . . . . . . . 50
7.2.2 Entity Length ............................................43 7.2.2 Entity Length . . . . . . . . . . . . . . . . . . . . 50
8 Connections ...................................................44 8 Connections . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.1 Persistent Connections ......................................44 8.1 Persistent Connections . . . . . . . . . . . . . . . . . 51
8.1.1 Purpose ..................................................44 8.1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . 51
8.1.2 Overall Operation ........................................45 8.1.2 Overall Operation . . . . . . . . . . . . . . . . . . 51
8.1.3 Proxy Servers ............................................46 8.1.3 Proxy Servers . . . . . . . . . . . . . . . . . . . . 53
8.1.4 Practical Considerations .................................46 8.1.4 Practical Considerations . . . . . . . . . . . . . . 53
8.2 Message Transmission Requirements ...........................47 8.2 Message Transmission Requirements . . . . . . . . . . . . 54
8.2.1 Persistent Connections and Flow Control ..................47 8.2.1 Persistent Connections and Flow Control . . . . . . . 54
8.2.2 Monitoring Connections for Error Status Messages .........48 8.2.2 Monitoring Connections for Error Status Messages . . 54
8.2.3 Use of the 100 (Continue) Status .........................48 8.2.3 Use of the 100 (Continue) Status . . . . . . . . . . 55
8.2.4 Client Behavior if Server Prematurely Closes Connection ..50 8.2.4 Client Behavior if Server Prematurely Closes
9 Method Definitions ............................................51 Connection . . . . . . . . . . . . . . . . . . . . . 57
9.1 Safe and Idempotent Methods .................................51 9 Method Definitions . . . . . . . . . . . . . . . . . . . . . 58
9.1.1 Safe Methods .............................................51 9.1 Safe and Idempotent Methods . . . . . . . . . . . . . . . 58
9.1.2 Idempotent Methods .......................................51 9.1.1 Safe Methods . . . . . . . . . . . . . . . . . . . . 58
9.2 OPTIONS .....................................................52 9.1.2 Idempotent Methods . . . . . . . . . . . . . . . . . 58
9.3 GET .........................................................53 9.2 OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 59
9.4 HEAD ........................................................54 9.3 GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
9.5 POST ........................................................54 9.4 HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . 60
9.6 PUT .........................................................55 9.5 POST . . . . . . . . . . . . . . . . . . . . . . . . . . 61
9.7 DELETE ......................................................56 9.6 PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
9.8 TRACE .......................................................56 9.7 DELETE . . . . . . . . . . . . . . . . . . . . . . . . . 63
9.9 CONNECT .....................................................57 9.8 TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 63
10 Status Code Definitions ......................................57 9.9 CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 64
10.1 Informational 1xx ...........................................57 10 Status Code Definitions . . . . . . . . . . . . . . . . . . . 65
10.1.1 100 Continue .............................................58 10.1 Informational 1xx . . . . . . . . . . . . . . . . . . . . 65
10.1.2 101 Switching Protocols ..................................58 10.1.1 100 Continue . . . . . . . . . . . . . . . . . . . . 65
10.2 Successful 2xx ..............................................58 10.1.2 101 Switching Protocols . . . . . . . . . . . . . . . 65
10.2.1 200 OK ...................................................58 10.2 Successful 2xx . . . . . . . . . . . . . . . . . . . . . 66
10.2.2 201 Created ..............................................59 10.2.1 200 OK . . . . . . . . . . . . . . . . . . . . . . . 66
10.2.3 202 Accepted .............................................59 10.2.2 201 Created . . . . . . . . . . . . . . . . . . . . . 66
10.2.4 203 Non-Authoritative Information ........................59 10.2.3 202 Accepted . . . . . . . . . . . . . . . . . . . . 66
10.2.5 204 No Content ...........................................60 10.2.4 203 Non-Authoritative Information . . . . . . . . . . 67
10.2.6 205 Reset Content ........................................60 10.2.5 204 No Content . . . . . . . . . . . . . . . . . . . 67
10.2.7 206 Partial Content ......................................60 10.2.6 205 Reset Content . . . . . . . . . . . . . . . . . . 67
10.3 Redirection 3xx .............................................61 10.2.7 206 Partial Content . . . . . . . . . . . . . . . . . 68
10.3.1 300 Multiple Choices .....................................61 10.3 Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 68
10.3.2 301 Moved Permanently ....................................62 10.3.1 300 Multiple Choices . . . . . . . . . . . . . . . . 69
10.3.3 302 Found ................................................62 10.3.2 301 Moved Permanently . . . . . . . . . . . . . . . . 69
10.3.4 303 See Other ............................................63 10.3.3 302 Found . . . . . . . . . . . . . . . . . . . . . . 70
10.3.5 304 Not Modified .........................................63 10.3.4 303 See Other . . . . . . . . . . . . . . . . . . . . 70
10.3.6 305 Use Proxy ............................................64 10.3.5 304 Not Modified . . . . . . . . . . . . . . . . . . 71
10.3.7 306 (Unused) .............................................64 10.3.6 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 71
10.3.8 307 Temporary Redirect ...................................65 10.3.7 306 (Unused) . . . . . . . . . . . . . . . . . . . . 72
10.4 Client Error 4xx ............................................65 10.3.8 307 Temporary Redirect . . . . . . . . . . . . . . . 72
10.4.1 400 Bad Request .........................................65 10.4 Client Error 4xx . . . . . . . . . . . . . . . . . . . . 72
10.4.2 401 Unauthorized ........................................66 10.4.1 400 Bad Request . . . . . . . . . . . . . . . . . . . 73
10.4.3 402 Payment Required ....................................66 10.4.2 401 Unauthorized . . . . . . . . . . . . . . . . . . 73
10.4.4 403 Forbidden ...........................................66 10.4.3 402 Payment Required . . . . . . . . . . . . . . . . 73
10.4.5 404 Not Found ...........................................66 10.4.4 403 Forbidden . . . . . . . . . . . . . . . . . . . . 73
10.4.6 405 Method Not Allowed ..................................66 10.4.5 404 Not Found . . . . . . . . . . . . . . . . . . . . 73
10.4.7 406 Not Acceptable ......................................67 10.4.6 405 Method Not Allowed . . . . . . . . . . . . . . . 74
10.4.8 407 Proxy Authentication Required .......................67 10.4.7 406 Not Acceptable . . . . . . . . . . . . . . . . . 74
10.4.9 408 Request Timeout .....................................67 10.4.8 407 Proxy Authentication Required . . . . . . . . . . 74
10.4.10 409 Conflict ............................................67 10.4.9 408 Request Timeout . . . . . . . . . . . . . . . . . 75
10.4.11 410 Gone ................................................68 10.4.10 409 Conflict . . . . . . . . . . . . . . . . . . . . 75
10.4.12 411 Length Required .....................................68 10.4.11 410 Gone . . . . . . . . . . . . . . . . . . . . . . 75
10.4.13 412 Precondition Failed .................................68 10.4.12 411 Length Required . . . . . . . . . . . . . . . . . 76
10.4.14 413 Request Entity Too Large ............................69 10.4.13 412 Precondition Failed . . . . . . . . . . . . . . . 76
10.4.15 414 Request-URI Too Long ................................69 10.4.14 413 Request Entity Too Large . . . . . . . . . . . . 76
10.4.16 415 Unsupported Media Type ..............................69 10.4.15 414 Request-URI Too Long . . . . . . . . . . . . . . 76
10.4.17 416 Requested Range Not Satisfiable .....................69 10.4.16 415 Unsupported Media Type . . . . . . . . . . . . . 76
10.4.18 417 Expectation Failed ..................................70 10.4.17 416 Requested Range Not Satisfiable . . . . . . . . . 76
10.5 Server Error 5xx ............................................70 10.4.18 417 Expectation Failed . . . . . . . . . . . . . . . 77
10.5.1 500 Internal Server Error ................................70 10.5 Server Error 5xx . . . . . . . . . . . . . . . . . . . . 77
10.5.2 501 Not Implemented ......................................70 10.5.1 500 Internal Server Error . . . . . . . . . . . . . . 77
10.5.3 502 Bad Gateway ..........................................70 10.5.2 501 Not Implemented . . . . . . . . . . . . . . . . . 77
10.5.4 503 Service Unavailable ..................................70 10.5.3 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 77
10.5.5 504 Gateway Timeout ......................................71 10.5.4 503 Service Unavailable . . . . . . . . . . . . . . . 78
10.5.6 505 HTTP Version Not Supported ...........................71 10.5.5 504 Gateway Timeout . . . . . . . . . . . . . . . . . 78
11 Access Authentication ........................................71 10.5.6 505 HTTP Version Not Supported . . . . . . . . . . . 78
12 Content Negotiation ..........................................71 11 Access Authentication . . . . . . . . . . . . . . . . . . . . 79
12.1 Server-driven Negotiation ...................................72 12 Content Negotiation . . . . . . . . . . . . . . . . . . . . . 80
12.2 Agent-driven Negotiation ....................................73 12.1 Server-driven Negotiation . . . . . . . . . . . . . . . . 80
12.3 Transparent Negotiation .....................................74 12.2 Agent-driven Negotiation . . . . . . . . . . . . . . . . 81
13 Caching in HTTP ..............................................74 12.3 Transparent Negotiation . . . . . . . . . . . . . . . . . 82
13.1.1 Cache Correctness ........................................75 13 Caching in HTTP . . . . . . . . . . . . . . . . . . . . . . . 83
13.1.2 Warnings .................................................76 13.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
13.1.3 Cache-control Mechanisms .................................77 13.1.1 Cache Correctness . . . . . . . . . . . . . . . . . . 84
13.1.4 Explicit User Agent Warnings .............................78 13.1.2 Warnings . . . . . . . . . . . . . . . . . . . . . . 85
13.1.5 Exceptions to the Rules and Warnings .....................78 13.1.3 Cache-control Mechanisms . . . . . . . . . . . . . . 86
13.1.6 Client-controlled Behavior ...............................79 13.1.4 Explicit User Agent Warnings . . . . . . . . . . . . 86
13.2 Expiration Model ............................................79 13.1.5 Exceptions to the Rules and Warnings . . . . . . . . 87
13.2.1 Server-Specified Expiration ..............................79 13.1.6 Client-controlled Behavior . . . . . . . . . . . . . 87
13.2.2 Heuristic Expiration .....................................80 13.2 Expiration Model . . . . . . . . . . . . . . . . . . . . 88
13.2.3 Age Calculations .........................................80 13.2.1 Server-Specified Expiration . . . . . . . . . . . . . 88
13.2.4 Expiration Calculations ..................................83 13.2.2 Heuristic Expiration . . . . . . . . . . . . . . . . 88
13.2.5 Disambiguating Expiration Values .........................84 13.2.3 Age Calculations . . . . . . . . . . . . . . . . . . 89
13.2.6 Disambiguating Multiple Responses ........................84 13.2.4 Expiration Calculations . . . . . . . . . . . . . . . 91
13.3 Validation Model ............................................85 13.2.5 Disambiguating Expiration Values . . . . . . . . . . 92
13.3.1 Last-Modified Dates ......................................86 13.2.6 Disambiguating Multiple Responses . . . . . . . . . . 93
13.3.2 Entity Tag Cache Validators ..............................86 13.3 Validation Model . . . . . . . . . . . . . . . . . . . . 93
13.3.3 Weak and Strong Validators ...............................86 13.3.1 Last-Modified Dates . . . . . . . . . . . . . . . . . 94
13.3.4 Rules for When to Use Entity Tags and Last-Modified Dates.89 13.3.2 Entity Tag Cache Validators . . . . . . . . . . . . . 94
13.3.5 Non-validating Conditionals ..............................90 13.3.3 Weak and Strong Validators . . . . . . . . . . . . . 95
13.4 Response Cacheability .......................................91 13.3.4 Rules for When to Use Entity Tags and
13.5 Constructing Responses From Caches ..........................92 Last-Modified Dates . . . . . . . . . . . . . . . . . 97
13.5.1 End-to-end and Hop-by-hop Headers ........................92 13.3.5 Non-validating Conditionals . . . . . . . . . . . . . 99
13.5.2 Non-modifiable Headers ...................................92 13.4 Response Cacheability . . . . . . . . . . . . . . . . . . 99
13.5.3 Combining Headers ........................................94 13.5 Constructing Responses From Caches . . . . . . . . . . . 100
13.5.4 Combining Byte Ranges ....................................95 13.5.1 End-to-end and Hop-by-hop Headers . . . . . . . . . . 100
13.6 Caching Negotiated Responses ................................95 13.5.2 Non-modifiable Headers . . . . . . . . . . . . . . . 101
13.7 Shared and Non-Shared Caches ................................96 13.5.3 Combining Headers . . . . . . . . . . . . . . . . . . 102
13.8 Errors or Incomplete Response Cache Behavior ................97 13.5.4 Combining Byte Ranges . . . . . . . . . . . . . . . . 103
13.9 Side Effects of GET and HEAD ................................97 13.6 Caching Negotiated Responses . . . . . . . . . . . . . . 104
13.10 Invalidation After Updates or Deletions ...................97 13.7 Shared and Non-Shared Caches . . . . . . . . . . . . . . 105
13.11 Write-Through Mandatory ...................................98 13.8 Errors or Incomplete Response Cache Behavior . . . . . . 105
13.12 Cache Replacement .........................................99 13.9 Side Effects of GET and HEAD . . . . . . . . . . . . . . 106
13.13 History Lists .............................................99 13.10 Invalidation After Updates or Deletions . . . . . . . . . 106
14 Header Field Definitions ....................................100 13.11 Write-Through Mandatory . . . . . . . . . . . . . . . . . 107
14.1 Accept .....................................................100 13.12 Cache Replacement . . . . . . . . . . . . . . . . . . . . 107
14.2 Accept-Charset .............................................102 13.13 History Lists . . . . . . . . . . . . . . . . . . . . . . 108
14.3 Accept-Encoding ............................................102 14 Header Field Definitions . . . . . . . . . . . . . . . . . . 109
14.4 Accept-Language ............................................104 14.1 Accept . . . . . . . . . . . . . . . . . . . . . . . . . 109
14.5 Accept-Ranges ..............................................105 14.2 Accept-Charset . . . . . . . . . . . . . . . . . . . . . 111
14.6 Age ........................................................106 14.3 Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 111
14.7 Allow ......................................................106 14.4 Accept-Language . . . . . . . . . . . . . . . . . . . . . 113
14.8 Authorization ..............................................107 14.5 Accept-Ranges . . . . . . . . . . . . . . . . . . . . . . 114
14.9 Cache-Control ..............................................108 14.6 Age . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
14.9.1 What is Cacheable .......................................109 14.7 Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 115
14.9.2 What May be Stored by Caches ............................110 14.8 Authorization . . . . . . . . . . . . . . . . . . . . . . 116
14.9.3 Modifications of the Basic Expiration Mechanism .........111 14.9 Cache-Control . . . . . . . . . . . . . . . . . . . . . . 116
14.9.4 Cache Revalidation and Reload Controls ..................113 14.9.1 What is Cacheable . . . . . . . . . . . . . . . . . . 118
14.9.5 No-Transform Directive ..................................115 14.9.2 What May be Stored by Caches . . . . . . . . . . . . 119
14.9.6 Cache Control Extensions ................................116 14.9.3 Modifications of the Basic Expiration Mechanism . . . 120
14.10 Connection ...............................................117 14.9.4 Cache Revalidation and Reload Controls . . . . . . . 122
14.11 Content-Encoding .........................................118 14.9.5 No-Transform Directive . . . . . . . . . . . . . . . 125
14.12 Content-Language .........................................118 14.9.6 Cache Control Extensions . . . . . . . . . . . . . . 125
14.13 Content-Length ...........................................119 14.10 Connection . . . . . . . . . . . . . . . . . . . . . . . 126
14.14 Content-Location .........................................120 14.11 Content-Encoding . . . . . . . . . . . . . . . . . . . . 127
14.15 Content-MD5 ..............................................121 14.12 Content-Language . . . . . . . . . . . . . . . . . . . . 128
14.16 Content-Range ............................................122 14.13 Content-Length . . . . . . . . . . . . . . . . . . . . . 128
14.17 Content-Type .............................................124 14.14 Content-Location . . . . . . . . . . . . . . . . . . . . 129
14.18 Date .....................................................124 14.15 Content-MD5 . . . . . . . . . . . . . . . . . . . . . . . 130
14.18.1 Clockless Origin Server Operation ......................125 14.16 Content-Range . . . . . . . . . . . . . . . . . . . . . . 131
14.19 ETag .....................................................126 14.17 Content-Type . . . . . . . . . . . . . . . . . . . . . . 133
14.20 Expect ...................................................126 14.18 Date . . . . . . . . . . . . . . . . . . . . . . . . . . 133
14.21 Expires ..................................................127 14.18.1 Clockless Origin Server Operation . . . . . . . . . . 134
14.22 From .....................................................128 14.19 ETag . . . . . . . . . . . . . . . . . . . . . . . . . . 135
14.23 Host .....................................................128 14.20 Expect . . . . . . . . . . . . . . . . . . . . . . . . . 135
14.24 If-Match .................................................129 14.21 Expires . . . . . . . . . . . . . . . . . . . . . . . . . 136
14.25 If-Modified-Since ........................................130 14.22 From . . . . . . . . . . . . . . . . . . . . . . . . . . 137
14.26 If-None-Match ............................................132 14.23 Host . . . . . . . . . . . . . . . . . . . . . . . . . . 137
14.27 If-Range .................................................133 14.24 If-Match . . . . . . . . . . . . . . . . . . . . . . . . 138
14.28 If-Unmodified-Since ......................................134 14.25 If-Modified-Since . . . . . . . . . . . . . . . . . . . . 139
14.29 Last-Modified ............................................134 14.26 If-None-Match . . . . . . . . . . . . . . . . . . . . . . 141
14.30 Location .................................................135 14.27 If-Range . . . . . . . . . . . . . . . . . . . . . . . . 142
14.31 Max-Forwards .............................................136 14.28 If-Unmodified-Since . . . . . . . . . . . . . . . . . . . 143
14.32 Pragma ...................................................136 14.29 Last-Modified . . . . . . . . . . . . . . . . . . . . . . 143
14.33 Proxy-Authenticate .......................................137 14.30 Location . . . . . . . . . . . . . . . . . . . . . . . . 144
14.34 Proxy-Authorization ......................................137 14.31 Max-Forwards . . . . . . . . . . . . . . . . . . . . . . 144
14.35 Range ....................................................138 14.32 Pragma . . . . . . . . . . . . . . . . . . . . . . . . . 145
14.35.1 Byte Ranges ...........................................138 14.33 Proxy-Authenticate . . . . . . . . . . . . . . . . . . . 146
14.35.2 Range Retrieval Requests ..............................139 14.34 Proxy-Authorization . . . . . . . . . . . . . . . . . . . 146
14.36 Referer ..................................................140 14.35 Range . . . . . . . . . . . . . . . . . . . . . . . . . . 147
14.37 Retry-After ..............................................141 14.35.1 Byte Ranges . . . . . . . . . . . . . . . . . . . . . 147
14.38 Server ...................................................141 14.35.2 Range Retrieval Requests . . . . . . . . . . . . . . 148
14.39 TE .......................................................142 14.36 Referer . . . . . . . . . . . . . . . . . . . . . . . . . 149
14.40 Trailer ..................................................143 14.37 Retry-After . . . . . . . . . . . . . . . . . . . . . . . 150
14.41 Transfer-Encoding..........................................143 14.38 Server . . . . . . . . . . . . . . . . . . . . . . . . . 150
14.42 Upgrade ..................................................144 14.39 TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
14.43 User-Agent ...............................................145 14.40 Trailer . . . . . . . . . . . . . . . . . . . . . . . . . 152
14.44 Vary .....................................................145 14.41 Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 152
14.45 Via ......................................................146 14.42 Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 153
14.46 Warning ..................................................148 14.43 User-Agent . . . . . . . . . . . . . . . . . . . . . . . 154
14.47 WWW-Authenticate .........................................150 14.44 Vary . . . . . . . . . . . . . . . . . . . . . . . . . . 154
15 Security Considerations .......................................150 14.45 Via . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
15.1 Personal Information....................................151 14.46 Warning . . . . . . . . . . . . . . . . . . . . . . . . . 157
15.1.1 Abuse of Server Log Information .........................151 14.47 WWW-Authenticate . . . . . . . . . . . . . . . . . . . . 159
15.1.2 Transfer of Sensitive Information .......................151 15 Security Considerations . . . . . . . . . . . . . . . . . . . 160
15.1.3 Encoding Sensitive Information in URI's .................152 15.1 Personal Information . . . . . . . . . . . . . . . . . . 160
15.1.4 Privacy Issues Connected to Accept Headers ..............152 15.1.1 Abuse of Server Log Information . . . . . . . . . . . 160
15.2 Attacks Based On File and Path Names .......................153 15.1.2 Transfer of Sensitive Information . . . . . . . . . . 160
15.3 DNS Spoofing ...............................................154 15.1.3 Encoding Sensitive Information in URI's . . . . . . . 161
15.4 Location Headers and Spoofing ..............................154 15.1.4 Privacy Issues Connected to Accept Headers . . . . . 162
15.5 Content-Disposition Issues .................................154 15.2 Attacks Based On File and Path Names . . . . . . . . . . 162
15.6 Authentication Credentials and Idle Clients ................155 15.3 DNS Spoofing . . . . . . . . . . . . . . . . . . . . . . 163
15.7 Proxies and Caching ........................................155 15.4 Location Headers and Spoofing . . . . . . . . . . . . . . 163
15.7.1 Denial of Service Attacks on Proxies....................156 15.5 Content-Disposition Issues . . . . . . . . . . . . . . . 164
16 Acknowledgments .............................................156 15.6 Authentication Credentials and Idle Clients . . . . . . . 164
17 References ..................................................158 15.7 Proxies and Caching . . . . . . . . . . . . . . . . . . . 164
18 Authors' Addresses ..........................................162 15.7.1 Denial of Service Attacks on Proxies . . . . . . . . 165
19 Appendices ..................................................164 16 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 166
19.1 Internet Media Type message/http and application/http ......164 16.1 (RFC2616) . . . . . . . . . . . . . . . . . . . . . . . . 166
19.2 Internet Media Type multipart/byteranges ...................165 16.2 (This Document) . . . . . . . . . . . . . . . . . . . . . 168
19.3 Tolerant Applications ......................................166 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 169
19.4 Differences Between HTTP Entities and RFC 2045 Entities ....167 17.1 References . . . . . . . . . . . . . . . . . . . . . . . 169
19.4.1 MIME-Version ............................................167 17.2 Normative References . . . . . . . . . . . . . . . . . . 172
19.4.2 Conversion to Canonical Form ............................167 Appendix A Internet Media Type message/http and
19.4.3 Conversion of Date Formats ..............................168 application/http . . . . . . . . . . . . . . . . . . 174
19.4.4 Introduction of Content-Encoding ........................168 Appendix B Internet Media Type multipart/byteranges . . . . . . 176
19.4.5 No Content-Transfer-Encoding ............................168 Appendix C Tolerant Applications . . . . . . . . . . . . . . . . 178
19.4.6 Introduction of Transfer-Encoding .......................169 Appendix D Differences Between HTTP Entities and RFC 2045
19.4.7 MHTML and Line Length Limitations .......................169 Entities . . . . . . . . . . . . . . . . . . . . . . 179
19.5 Additional Features ........................................169 D.1 MIME-Version . . . . . . . . . . . . . . . . . . . . . . 179
19.5.1 Content-Disposition .....................................170 D.2 Conversion to Canonical Form . . . . . . . . . . . . . . 179
19.6 Compatibility with Previous Versions .......................170 D.3 Conversion of Date Formats . . . . . . . . . . . . . . . 180
19.6.1 Changes from HTTP/1.0 ...................................171 D.4 Introduction of Content-Encoding . . . . . . . . . . . . 180
19.6.2 Compatibility with HTTP/1.0 Persistent Connections ......172 D.5 No Content-Transfer-Encoding . . . . . . . . . . . . . . 180
19.6.3 Changes from RFC 2068 ...................................172 D.6 Introduction of Transfer-Encoding . . . . . . . . . . . . 181
20 Index .......................................................175 D.7 MHTML and Line Length Limitations . . . . . . . . . . . . 181
21 Full Copyright Statement ....................................176 Appendix E Additional Features . . . . . . . . . . . . . . . . . 182
E.1 Content-Disposition . . . . . . . . . . . . . . . . . . . 182
Appendix F Compatibility with Previous Versions . . . . . . . . 183
F.1 Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 183
F.1.1 Changes to Simplify Multi-homed Web Servers and
Conserve IP Addresses . . . . . . . . . . . . . . . . 183
F.2 Compatibility with HTTP/1.0 Persistent Connections . . . 184
F.3 Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 185
Appendix G Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 188
G.1 Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 188
Appendix H Open issues (to be removed by RFC Editor prior to
publication) . . . . . . . . . . . . . . . . . . . . 189
H.1 rfc2616bis . . . . . . . . . . . . . . . . . . . . . . . 189
H.2 edit . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 201
Intellectual Property and Copyright Statements . . . . . . . . . 202
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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access to resources available from diverse applications. access to resources available from diverse applications.
1.2 Requirements 1.2 Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [34]. document are to be interpreted as described in RFC 2119 [34].
An implementation is not compliant if it fails to satisfy one or more An implementation is not compliant if it fails to satisfy one or more
of the MUST or REQUIRED level requirements for the protocols it of the MUST or REQUIRED level requirements for the protocols it
implements. An implementation that satisfies all the MUST or REQUIRED implements. An implementation that satisfies all the MUST or
level and all the SHOULD level requirements for its protocols is said REQUIRED level and all the SHOULD level requirements for its
to be "unconditionally compliant"; one that satisfies all the MUST protocols is said to be "unconditionally compliant"; one that
level requirements but not all the SHOULD level requirements for its satisfies all the MUST level requirements but not all the SHOULD
protocols is said to be "conditionally compliant." level requirements for its protocols is said to be "conditionally
compliant."
1.3 Terminology 1.3 Terminology
This specification uses a number of terms to refer to the roles This specification uses a number of terms to refer to the roles
played by participants in, and objects of, the HTTP communication. played by participants in, and objects of, the HTTP communication.
connection connection
A transport layer virtual circuit established between two programs A transport layer virtual circuit established between two programs
for the purpose of communication. for the purpose of communication.
message message
The basic unit of HTTP communication, consisting of a structured The basic unit of HTTP communication, consisting of a structured
sequence of octets matching the syntax defined in section 4 and sequence of octets matching the syntax defined in section 4 and
transmitted via the connection. transmitted via the connection.
request request
An HTTP request message, as defined in section 5. An HTTP request message, as defined in section 5.
response response
An HTTP response message, as defined in section 6. An HTTP response message, as defined in section 6.
resource resource
A network data object or service that can be identified by a URI, A network data object or service that can be identified by a URI,
as defined in section 3.2. Resources may be available in multiple as defined in section 3.2. Resources may be available in multiple
representations (e.g. multiple languages, data formats, size, and representations (e.g. multiple languages, data formats, size, and
resolutions) or vary in other ways. resolutions) or vary in other ways.
entity entity
The information transferred as the payload of a request or The information transferred as the payload of a request or
response. An entity consists of metainformation in the form of response. An entity consists of metainformation in the form of
entity-header fields and content in the form of an entity-body, as entity-header fields and content in the form of an entity-body, as
described in section 7. described in section 7.
representation representation
An entity included with a response that is subject to content An entity included with a response that is subject to content
negotiation, as described in section 12. There may exist multiple negotiation, as described in section 12. There may exist multiple
representations associated with a particular response status. representations associated with a particular response status.
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An application program that accepts connections in order to An application program that accepts connections in order to
service requests by sending back responses. Any given program may service requests by sending back responses. Any given program may
be capable of being both a client and a server; our use of these be capable of being both a client and a server; our use of these
terms refers only to the role being performed by the program for a terms refers only to the role being performed by the program for a
particular connection, rather than to the program's capabilities particular connection, rather than to the program's capabilities
in general. Likewise, any server may act as an origin server, in general. Likewise, any server may act as an origin server,
proxy, gateway, or tunnel, switching behavior based on the nature proxy, gateway, or tunnel, switching behavior based on the nature
of each request. of each request.
origin server origin server
The server on which a given resource resides or is to be created. The server on which a given resource resides or is to be created.
proxy proxy
An intermediary program which acts as both a server and a client An intermediary program which acts as both a server and a client
for the purpose of making requests on behalf of other clients. for the purpose of making requests on behalf of other clients.
Requests are serviced internally or by passing them on, with Requests are serviced internally or by passing them on, with
possible translation, to other servers. A proxy MUST implement possible translation, to other servers. A proxy MUST implement
both the client and server requirements of this specification. A both the client and server requirements of this specification. A
"transparent proxy" is a proxy that does not modify the request or "transparent proxy" is a proxy that does not modify the request or
response beyond what is required for proxy authentication and response beyond what is required for proxy authentication and
identification. A "non-transparent proxy" is a proxy that modifies identification. A "non-transparent proxy" is a proxy that
the request or response in order to provide some added service to modifies the request or response in order to provide some added
the user agent, such as group annotation services, media type service to the user agent, such as group annotation services,
transformation, protocol reduction, or anonymity filtering. Except media type transformation, protocol reduction, or anonymity
where either transparent or non-transparent behavior is explicitly filtering. Except where either transparent or non-transparent
stated, the HTTP proxy requirements apply to both types of behavior is explicitly stated, the HTTP proxy requirements apply
proxies. to both types of proxies.
gateway gateway
A server which acts as an intermediary for some other server. A server which acts as an intermediary for some other server.
Unlike a proxy, a gateway receives requests as if it were the Unlike a proxy, a gateway receives requests as if it were the
origin server for the requested resource; the requesting client origin server for the requested resource; the requesting client
may not be aware that it is communicating with a gateway. may not be aware that it is communicating with a gateway.
tunnel tunnel
An intermediary program which is acting as a blind relay between An intermediary program which is acting as a blind relay between
two connections. Once active, a tunnel is not considered a party two connections. Once active, a tunnel is not considered a party
to the HTTP communication, though the tunnel may have been to the HTTP communication, though the tunnel may have been
initiated by an HTTP request. The tunnel ceases to exist when both initiated by an HTTP request. The tunnel ceases to exist when
ends of the relayed connections are closed. both ends of the relayed connections are closed.
cache cache
A program's local store of response messages and the subsystem A program's local store of response messages and the subsystem
that controls its message storage, retrieval, and deletion. A that controls its message storage, retrieval, and deletion. A
cache stores cacheable responses in order to reduce the response cache stores cacheable responses in order to reduce the response
time and network bandwidth consumption on future, equivalent time and network bandwidth consumption on future, equivalent
requests. Any client or server may include a cache, though a cache requests. Any client or server may include a cache, though a
cannot be used by a server that is acting as a tunnel. cache cannot be used by a server that is acting as a tunnel.
cacheable cacheable
A response is cacheable if a cache is allowed to store a copy of A response is cacheable if a cache is allowed to store a copy of
the response message for use in answering subsequent requests. The the response message for use in answering subsequent requests.
rules for determining the cacheability of HTTP responses are The rules for determining the cacheability of HTTP responses are
defined in section 13. Even if a resource is cacheable, there may defined in section 13. Even if a resource is cacheable, there may
be additional constraints on whether a cache can use the cached be additional constraints on whether a cache can use the cached
copy for a particular request. copy for a particular request.
first-hand first-hand
A response is first-hand if it comes directly and without A response is first-hand if it comes directly and without
unnecessary delay from the origin server, perhaps via one or more unnecessary delay from the origin server, perhaps via one or more
proxies. A response is also first-hand if its validity has just proxies. A response is also first-hand if its validity has just
been checked directly with the origin server. been checked directly with the origin server.
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1.4 Overall Operation 1.4 Overall Operation
The HTTP protocol is a request/response protocol. A client sends a The HTTP protocol is a request/response protocol. A client sends a
request to the server in the form of a request method, URI, and request to the server in the form of a request method, URI, and
protocol version, followed by a MIME-like message containing request protocol version, followed by a MIME-like message containing request
modifiers, client information, and possible body content over a modifiers, client information, and possible body content over a
connection with a server. The server responds with a status line, connection with a server. The server responds with a status line,
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 19.4. 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
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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 may along the chain. Although the diagram is linear, each participant
be engaged in multiple, simultaneous communications. For example, B may be engaged in multiple, simultaneous communications. For
may be receiving requests from many clients other than A, and/or example, B may be receiving requests from many clients other than A,
forwarding requests to servers other than C, at the same time that it and/or forwarding requests to servers other than C, at the same time
is handling A's request. that it is handling A's request.
Any party to the communication which is not acting as a tunnel may Any party to the communication which is not acting as a tunnel may
employ an internal cache for handling requests. The effect of a cache employ an internal cache for handling requests. The effect of a
is that the request/response chain is shortened if one of the cache is that the request/response chain is shortened if one of the
participants along the chain has a cached response applicable to that participants along the chain has a cached response applicable to that
request. The following illustrates the resulting chain if B has a request. The following illustrates the resulting chain if B has a
cached copy of an earlier response from O (via C) for a request which cached copy of an earlier response from O (via C) for a request which
has not been cached by UA or A. has not been cached by UA or A.
request chain ----------> request chain ---------->
UA -----v----- A -----v----- B - - - - - - C - - - - - - O UA -----v----- A -----v----- B - - - - - - C - - - - - - O
<--------- response chain <--------- response chain
Not all responses are usefully cacheable, and some requests may Not all responses are usefully cacheable, and some requests may
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one or more request/response exchanges, although connections may be one or more request/response exchanges, although connections may be
closed for a variety of reasons (see section 8.1). closed for a variety of reasons (see section 8.1).
2 Notational Conventions and Generic Grammar 2 Notational Conventions and Generic Grammar
2.1 Augmented BNF 2.1 Augmented BNF
All of the mechanisms specified in this document are described in All of the mechanisms specified in this document are described in
both prose and an augmented Backus-Naur Form (BNF) similar to that both prose and an augmented Backus-Naur Form (BNF) similar to that
used by RFC 822 [9]. Implementors will need to be familiar with the used by RFC 822 [9]. Implementors will need to be familiar with the
notation in order to understand this specification. The augmented BNF notation in order to understand this specification. The augmented
includes the following constructs: BNF includes the following constructs:
name = definition name = definition
The name of a rule is simply the name itself (without any The name of a rule is simply the name itself (without any
enclosing "<" and ">") and is separated from its definition by the enclosing "<" and ">") and is separated from its definition by the
equal "=" character. White space is only significant in that equal "=" character. White space is only significant in that
indentation of continuation lines is used to indicate a rule indentation of continuation lines is used to indicate a rule
definition that spans more than one line. Certain basic rules are definition that spans more than one line. Certain basic rules are
in uppercase, such as SP, LWS, HT, CRLF, DIGIT, ALPHA, etc. Angle in uppercase, such as SP, LWS, HT, CRLF, DIGIT, ALPHA, etc. Angle
brackets are used within definitions whenever their presence will brackets are used within definitions whenever their presence will
facilitate discerning the use of rule names. facilitate discerning the use of rule names.
"literal" "literal"
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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 19.3 for protocol elements except the entity-body (see appendix C for tolerant
tolerant applications). The end-of-line marker within an entity-body applications). The end-of-line marker within an entity-body is
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 )
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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 section string to be used within a parameter value (as defined in
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.
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changed. See RFC 2145 [36] for a fuller explanation. changed. See RFC 2145 [36] for a fuller explanation.
The version of an HTTP message is indicated by an HTTP-Version field The version of an HTTP message is indicated by an HTTP-Version field
in the first line of the message. in the first line of the message.
HTTP-Version = "HTTP" "/" 1*DIGIT "." 1*DIGIT HTTP-Version = "HTTP" "/" 1*DIGIT "." 1*DIGIT
Note that the major and minor numbers MUST be treated as separate Note that the major and minor numbers MUST be treated as separate
integers and that each MAY be incremented higher than a single digit. integers and that each MAY be incremented higher than a single digit.
Thus, HTTP/2.4 is a lower version than HTTP/2.13, which in turn is Thus, HTTP/2.4 is a lower version than HTTP/2.13, which in turn is
lower than HTTP/12.3. Leading zeros MUST be ignored by recipients and lower than HTTP/12.3. Leading zeros MUST be ignored by recipients
MUST NOT be sent. and MUST NOT be sent.
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 conditionally with this specification. Applications that are at least
compliant with this specification SHOULD use an HTTP-Version of conditionally compliant with this specification SHOULD use an HTTP-
"HTTP/1.1" in their messages, and MUST do so for any message that is Version of "HTTP/1.1" in their messages, and MUST do so for any
not compatible with HTTP/1.0. For more details on when to send message that is not compatible with HTTP/1.0. For more details on
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.
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.
Due to interoperability problems with HTTP/1.0 proxies discovered Due to interoperability problems with HTTP/1.0 proxies discovered
since the publication of RFC 2068[33], caching proxies MUST, gateways since the publication of RFC 2068 [33], caching proxies MUST,
MAY, and tunnels MUST NOT upgrade the request to the highest version gateways MAY, and tunnels MUST NOT upgrade the request to the highest
they support. The proxy/gateway's response to that request MUST be in version they support. The proxy/gateway's response to that request
the same major version as the request. MUST be in the same major version as the request.
Note: Converting between versions of HTTP may involve modification Note: Converting between versions of HTTP may involve modification
of header fields required or forbidden by the versions involved. of header fields required or forbidden by the versions involved.
3.2 Uniform Resource Identifiers 3.2 Uniform Resource Identifiers
URIs have been known by many names: WWW addresses, Universal Document URIs have been known by many names: WWW addresses, Universal Document
Identifiers, Universal Resource Identifiers [3], and finally the Identifiers, Universal Resource Identifiers [3], and finally the
combination of Uniform Resource Locators (URL) [4] and Names (URN) combination of Uniform Resource Locators (URL) [4] and Names (URN)
[20]. As far as HTTP is concerned, Uniform Resource Identifiers are [20]. As far as HTTP is concerned, Uniform Resource Identifiers are
simply formatted strings which identify--via name, location, or any simply formatted strings which identify--via name, location, or any
other characteristic--a resource. other characteristic--a resource.
3.2.1 General Syntax 3.2.1 General Syntax
URIs in HTTP can be represented in absolute form or relative to some URIs in HTTP can be represented in absolute form or relative to some
known base URI [11], depending upon the context of their use. The two known base URI [11], depending upon the context of their use. The
forms are differentiated by the fact that absolute URIs always begin two forms are differentiated by the fact that absolute URIs always
with a scheme name followed by a colon. For definitive information on begin with a scheme name followed by a colon. For definitive
URL syntax and semantics, see "Uniform Resource Identifiers (URI): information on URL syntax and semantics, see "Uniform Resource
Generic Syntax and Semantics," RFC 2396 [42] (which replaces RFCs Identifiers (URI): Generic Syntax and Semantics," RFC 2396 [42]
1738 [4] and RFC 1808 [11]). This specification adopts the (which replaces RFCs 1738 [4] and RFC 1808 [11]). This specification
definitions of "URI-reference", "absoluteURI", "relativeURI", "port", adopts the definitions of "URI-reference", "absoluteURI",
"host","abs_path", "rel_path", and "authority" from that "relativeURI", "port", "host","abs_path", "rel_path", and "authority"
specification. from that specification.
The HTTP protocol does not place any a priori limit on the length of The HTTP protocol does not place any a priori limit on the length of
a URI. Servers MUST be able to handle the URI of any resource they a URI. Servers MUST be able to handle the URI of any resource they
serve, and SHOULD be able to handle URIs of unbounded length if they serve, and SHOULD be able to handle URIs of unbounded length if they
provide GET-based forms that could generate such URIs. A server provide GET-based forms that could generate such URIs. A server
SHOULD return 414 (Request-URI Too Long) status if a URI is longer SHOULD return 414 (Request-URI Too Long) status if a URI is longer
than the server can handle (see section 10.4.15). than the server can handle (see section 10.4.15).
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
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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 addresses for the resource is abs_path (section 5.1.2). The use of IP
in URLs SHOULD be avoided whenever possible (see RFC 1900 [24]). If addresses in URLs SHOULD be avoided whenever possible (see RFC 1900
the abs_path is not present in the URL, it MUST be given as "/" when [24]). If the abs_path is not present in the URL, it MUST be given
used as a Request-URI for a resource (section 5.1.2). If a proxy as "/" when used as a Request-URI for a resource (section 5.1.2). If
receives a host name which is not a fully qualified domain name, it a proxy receives a host name which is not a fully qualified domain
MAY add its domain to the host name it received. If a proxy receives name, it MAY add its domain to the host name it received. If a proxy
a fully qualified domain name, the proxy MUST NOT change the host receives a fully qualified domain name, the proxy MUST NOT change the
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:
- 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;
- Comparisons of host names MUST be case-insensitive; o Comparisons of host names MUST be case-insensitive;
- Comparisons of scheme names MUST be case-insensitive; o Comparisons of scheme names MUST be case-insensitive;
- 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" and "unsafe" sets (see
RFC 2396 [42]) are equivalent to their ""%" HEX HEX" encoding. RFC 2396 [42]) 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
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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 the RFC 822 [9]). The second format is in common use, but is based on
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 section 19.3 for further information. in header fields. See appendix C for further information.
Note: Recipients of date values are encouraged to be robust in Note: Recipients of date values are encouraged to be robust in
accepting date values that may have been sent by non-HTTP accepting date values that may have been sent by non-HTTP
applications, as is sometimes the case when retrieving or posting applications, as is sometimes the case when retrieving or posting
messages via proxies/gateways to SMTP or NNTP. messages via proxies/gateways to SMTP or NNTP.
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
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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 Note: HTTP requirements for the date/time stamp format apply only to
to their usage within the protocol stream. Clients and servers are their usage within the protocol stream. Clients and servers are not
not required to use these formats for user presentation, request required to use these formats for user presentation, request logging,
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
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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
following tokens: following tokens:
gzip An encoding format produced by the file compression program gzip
"gzip" (GNU zip) as described in RFC 1952 [25]. This format is a
Lempel-Ziv coding (LZ77) with a 32 bit CRC. An encoding format produced by the file compression program "gzip"
(GNU zip) as described in RFC 1952 [25]. This format is a Lempel-
Ziv coding (LZ77) with a 32 bit CRC.
compress compress
The encoding format produced by the common UNIX file compression The encoding format produced by the common UNIX file compression
program "compress". This format is an adaptive Lempel-Ziv-Welch program "compress". This format is an adaptive Lempel-Ziv-Welch
coding (LZW). coding (LZW).
Use of program names for the identification of encoding formats Use of program names for the identification of encoding formats is
is not desirable and is discouraged for future encodings. Their not desirable and is discouraged for future encodings. Their use
use here is representative of historical practice, not good here is representative of historical practice, not good design.
design. For compatibility with previous implementations of HTTP, For compatibility with previous implementations of HTTP,
applications SHOULD consider "x-gzip" and "x-compress" to be applications SHOULD consider "x-gzip" and "x-compress" to be
equivalent to "gzip" and "compress" respectively. equivalent to "gzip" and "compress" respectively.
deflate deflate
The "zlib" format defined in RFC 1950 [31] in combination with
the "deflate" compression mechanism described in RFC 1951 [29]. The "zlib" format defined in RFC 1950 [31] in combination with the
"deflate" compression mechanism described in RFC 1951 [29].
identity identity
The default (identity) encoding; the use of no transformation The default (identity) encoding; the use of no transformation
whatsoever. This content-coding is used only in the Accept- whatsoever. This content-coding is used only in the Accept-
Encoding header, and SHOULD NOT be used in the Content-Encoding Encoding header, and SHOULD NOT be used in the Content-Encoding
header. header.
New content-coding value tokens SHOULD be registered; to allow New content-coding value tokens SHOULD be registered; to allow
interoperability between clients and servers, specifications of the interoperability between clients and servers, specifications of the
content coding algorithms needed to implement a new value SHOULD be content coding algorithms needed to implement a new value SHOULD be
publicly available and adequate for independent implementation, and publicly available and adequate for independent implementation, and
conform to the purpose of content coding defined in this section. conform to the purpose of content coding defined in this section.
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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. This followed by an OPTIONAL trailer containing entity-header fields.
allows dynamically produced content to be transferred along with the This allows dynamically produced content to be transferred along with
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
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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:
a)the request included a TE header field that indicates "trailers" is 1. the request included a TE header field that indicates "trailers"
acceptable in the transfer-coding of the response, as described in is acceptable in the transfer-coding of the response, as
section 14.39; or, described in section 14.39; or,
b)the server is the origin server for the response, the trailer 2. the server is the origin server for the response, the trailer
fields consist entirely of optional metadata, and the recipient fields consist entirely of optional metadata, and the recipient
could use the message (in a manner acceptable to the origin server) could use the message (in a manner acceptable to the origin
without receiving this metadata. In other words, the origin server server) without receiving this metadata. In other words, the
is willing to accept the possibility that the trailer fields might origin server is willing to accept the possibility that the
be silently discarded along the path to the client. trailer fields might be silently discarded along the path to the
client.
This requirement prevents an interoperability failure when the This requirement prevents an interoperability failure when the
message is being received by an HTTP/1.1 (or later) proxy and message is being received by an HTTP/1.1 (or later) proxy and
forwarded to an HTTP/1.0 recipient. It avoids a situation where forwarded to an HTTP/1.0 recipient. It avoids a situation where
compliance with the protocol would have necessitated a possibly compliance with the protocol would have necessitated a possibly
infinite buffer on the proxy. infinite buffer on the proxy.
An example process for decoding a Chunked-Body is presented in An example process for decoding a Chunked-Body is presented in
appendix 19.4.6. appendix D.6.
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 (section HTTP uses Internet Media Types [17] in the Content-Type
14.17) and Accept (section 14.1) header fields in order to provide (section 14.17) and Accept (section 14.1) header fields in order to
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 might attribute and its value. The presence or absence of a parameter
be significant to the processing of a media-type, depending on its might be significant to the processing of a media-type, depending on
definition within the media type registry. its definition within the media type registry.
Note that some older HTTP applications do not recognize media type Note that some older HTTP applications do not recognize media type
parameters. When sending data to older HTTP applications, parameters. When sending data to older HTTP applications,
implementations SHOULD only use media type parameters when they are implementations SHOULD only use media type parameters when they are
required by that type/subtype definition. required by that type/subtype definition.
Media-type values are registered with the Internet Assigned Number Media-type values are registered with the Internet Assigned Number
Authority (IANA [19]). The media type registration process is Authority (IANA [19]). The media type registration process is
outlined in RFC 1590 [17]. Use of non-registered media types is outlined in RFC 1590 [17]. Use of non-registered media types is
discouraged. discouraged.
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3.7.2 Multipart Types 3.7.2 Multipart Types
MIME provides for a number of "multipart" types -- encapsulations of MIME provides for a number of "multipart" types -- encapsulations of
one or more entities within a single message-body. All multipart one or more entities within a single message-body. All multipart
types share a common syntax, as defined in section 5.1.1 of RFC 2046 types share a common syntax, as defined in section 5.1.1 of RFC 2046
[40], and MUST include a boundary parameter as part of the media type [40], and MUST include a boundary parameter as part of the media type
value. The message body is itself a protocol element and MUST value. The message body is itself a protocol element and MUST
therefore use only CRLF to represent line breaks between body-parts. therefore use only CRLF to represent line breaks between body-parts.
Unlike in RFC 2046, the epilogue of any multipart message MUST be Unlike in RFC 2046, the epilogue of any multipart message MUST be
empty; HTTP applications MUST NOT transmit the epilogue (even if the empty; HTTP applications MUST NOT transmit the epilogue (even if the
original multipart contains an epilogue). These restrictions exist in original multipart contains an epilogue). These restrictions exist
order to preserve the self-delimiting nature of a multipart message- in order to preserve the self-delimiting nature of a multipart
body, wherein the "end" of the message-body is indicated by the message-body, wherein the "end" of the message-body is indicated by
ending multipart boundary. the ending multipart boundary.
In general, HTTP treats a multipart message-body no differently than In general, HTTP treats a multipart message-body no differently than
any other media type: strictly as payload. The one exception is the any other media type: strictly as payload. The one exception is the
"multipart/byteranges" type (appendix 19.2) when it appears in a 206 "multipart/byteranges" type (appendix B) when it appears in a 206
(Partial Content) response, which will be interpreted by some HTTP (Partial Content) response, which will be interpreted by some HTTP
caching mechanisms as described in sections 13.5.4 and 14.16. In all caching mechanisms as described in sections 13.5.4 and 14.16. In all
other cases, an HTTP user agent SHOULD follow the same or similar other cases, an HTTP user agent SHOULD follow the same or similar
behavior as a MIME user agent would upon receipt of a multipart type. behavior as a MIME user agent would upon receipt of a multipart type.
The MIME header fields within each body-part of a multipart message- The MIME header fields within each body-part of a multipart message-
body do not have any significance to HTTP beyond that defined by body do not have any significance to HTTP beyond that defined by
their MIME semantics. their MIME semantics.
In general, an HTTP user agent SHOULD follow the same or similar In general, an HTTP user agent SHOULD follow the same or similar
behavior as a MIME user agent would upon receipt of a multipart type. behavior as a MIME user agent would upon receipt of a multipart type.
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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 any used for advertising or other non-essential information. Although
token character MAY appear in a product-version, this token SHOULD any token character MAY appear in a product-version, this token
only be used for a version identifier (i.e., successive versions of SHOULD only be used for a version identifier (i.e., successive
the same product SHOULD only differ in the product-version portion of versions of the same product SHOULD only differ in the product-
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
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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 (section requested resource. HTTP/1.1 uses entity tags in the ETag
14.19), If-Match (section 14.24), If-None-Match (section 14.26), and (section 14.19), If-Match (section 14.24), If-None-Match
If-Range (section 14.27) header fields. The definition of how they (section 14.26), and If-Range (section 14.27) header fields. The
are used and compared as cache validators is in section 13.3.3. An definition of how they are used and compared as cache validators is
entity tag consists of an opaque quoted string, possibly prefixed by in section 13.3.3. An entity tag consists of an opaque quoted
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
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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, if line(s) received where a Request-Line is expected. In other words,
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.
4.2 Message Headers 4.2 Message Headers
HTTP header fields, which include general-header (section 4.5), HTTP header fields, which include general-header (section 4.5),
request-header (section 5.3), response-header (section 6.2), and request-header (section 5.3), response-header (section 6.2), and
entity-header (section 7.1) fields, follow the same generic format as entity-header (section 7.1) fields, follow the same generic format as
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", where least one SP or HT. Applications ought to follow "common form",
one is known or indicated, when generating HTTP constructs, since where one is known or indicated, when generating HTTP constructs,
there might exist some implementations that fail to accept anything since there might exist some implementations that fail to accept
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
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"field-name: field-value" pair, without changing the semantics of the "field-name: field-value" pair, without changing the semantics of the
message, by appending each subsequent field-value to the first, each message, by appending each subsequent field-value to the first, each
separated by a comma. The order in which header fields with the same separated by a comma. The order in which header fields with the same
field-name are received is therefore significant to the field-name are received is therefore significant to the
interpretation of the combined field value, and thus a proxy MUST NOT interpretation of the combined field value, and thus a proxy MUST NOT
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-body entity-body associated with the request or response. The message-
differs from the entity-body only when a transfer-coding has been body differs from the entity-body only when a transfer-coding has
applied, as indicated by the Transfer-Encoding header field (section been applied, as indicated by the Transfer-Encoding header field
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.
The presence of a message-body in a request is signaled by the The presence of a message-body in a request is signaled by the
inclusion of a Content-Length or Transfer-Encoding header field in inclusion of a Content-Length or Transfer-Encoding header field in
the request's message-headers. A message-body MUST NOT be included in the request's message-headers. A message-body MUST NOT be included
a request if the specification of the request method (section 5.1.1) in a request if the specification of the request method
does not allow sending an entity-body in requests. A server SHOULD (section 5.1.1) does not allow sending an entity-body in requests. A
read and forward a message-body on any request; if the request method server SHOULD read and forward a message-body on any request; if the
does not include defined semantics for an entity-body, then the request method does not include defined semantics for an entity-body,
message-body SHOULD be ignored when handling the request. then the message-body SHOULD be ignored when handling the request.
For response messages, whether or not a message-body is included with For response messages, whether or not a message-body is included with
a message is dependent on both the request method and the response a message is dependent on both the request method and the response
status code (section 6.1.1). All responses to the HEAD request method status code (section 6.1.1). All responses to the HEAD request
MUST NOT include a message-body, even though the presence of entity- method MUST NOT include a message-body, even though the presence of
header fields might lead one to believe they do. All 1xx entity-header fields might lead one to believe they do. All 1xx
(informational), 204 (no content), and 304 (not modified) responses (informational), 204 (no content), and 304 (not modified) responses
MUST NOT include a message-body. All other responses do include a MUST NOT include a message-body. All other responses do include a
message-body, although it MAY be of zero length. message-body, although it MAY be of zero length.
4.4 Message Length 4.4 Message Length
The transfer-length of a message is the length of the message-body as The transfer-length of a message is the length of the message-body as
it appears in the message; that is, after any transfer-codings have it appears in the message; that is, after any transfer-codings have
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 (such 1. Any response message which "MUST NOT" include a message-body
as the 1xx, 204, and 304 responses and any response to a HEAD (such as the 1xx, 204, and 304 responses and any response to a
request) is always terminated by the first empty line after the HEAD request) is always terminated by the first empty line after
header fields, regardless of the entity-header fields present in the header fields, regardless of the entity-header fields present
the message. in the message.
2.If a Transfer-Encoding header field (section 14.41) is present and 2. If a Transfer-Encoding header field (section 14.41) is present
has any value other than "identity", then the transfer-length is and has any value other than "identity", then the transfer-length
defined by use of the "chunked" transfer-coding (section 3.6), is defined by use of the "chunked" transfer-coding (section 3.6),
unless the message is terminated by closing the connection. unless the message is terminated 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 sent transfer-length. The Content-Length header field MUST NOT be
if these two lengths are different (i.e., if a Transfer-Encoding sent if these two lengths are different (i.e., if a Transfer-
header field is present). If a message is received with both a Encoding header field is present). If a message is received with
Transfer-Encoding header field and a Content-Length header field, both a Transfer-Encoding header field and a Content-Length header
the latter MUST be ignored. field, the latter MUST be ignored.
4.If the message uses the media type "multipart/byteranges", and the 4. If the message uses the media type "multipart/byteranges", and
ransfer-length is not otherwise specified, then this self- the ransfer-length is not otherwise specified, then this self-
elimiting media type defines the transfer-length. This media type elimiting media type defines the transfer-length. This media
UST NOT be used unless the sender knows that the recipient can arse type UST NOT be used unless the sender knows that the recipient
it; the presence in a request of a Range header with ultiple byte- can arse it; the presence in a request of a Range header with
range specifiers from a 1.1 client implies that the lient can parse ultiple byte-range specifiers from a 1.1 client implies that the
multipart/byteranges responses. lient 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 of delimit the message using methods defined in items 1, 3 or 5
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 response.) would leave no possibility for the server to send back a
response.)
For compatibility with HTTP/1.0 applications, HTTP/1.1 requests For compatibility with HTTP/1.0 applications, HTTP/1.1 requests
containing a message-body MUST include a valid Content-Length header containing a message-body MUST include a valid Content-Length header
field unless the server is known to be HTTP/1.1 compliant. If a field unless the server is known to be HTTP/1.1 compliant. If a
request contains a message-body and a Content-Length is not given, request contains a message-body and a Content-Length is not given,
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
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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 The Request-Line begins with a method token, followed by the Request-
Request-URI and the protocol version, and ending with CRLF. The URI and the protocol version, and ending with CRLF. The elements are
elements are separated by SP characters. No CR or LF is allowed separated by SP characters. No CR or LF is allowed except in the
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 The Method token indicates the method to be performed on the resource
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. An resource, since the set of allowed methods can change dynamically.
origin server SHOULD return the status code 405 (Method Not Allowed) An origin server SHOULD return the status code 405 (Method Not
if the method is known by the origin server but not allowed for the Allowed) if the method is known by the origin server but not allowed
requested resource, and 501 (Not Implemented) if the method is for the requested resource, and 501 (Not Implemented) if the method
unrecognized or not implemented by the origin server. The methods GET is unrecognized or not implemented by the origin server. The methods
and HEAD MUST be supported by all general-purpose servers. All other GET and HEAD MUST be supported by all general-purpose servers. All
methods are OPTIONAL; however, if the above methods are implemented, other methods are OPTIONAL; however, if the above methods are
they MUST be implemented with the same semantics as those specified implemented, they MUST be implemented with the same semantics as
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 | 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
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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 example any aliases, local variations, and the numeric IP address. An
Request-Line would be: example Request-Line would be:
GET http://www.w3.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.w3.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).
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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.w3.org" and send
the lines: the lines:
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.w3.org Host: www.w3.org
followed by the remainder of the Request. Note that the absolute
followed by the remainder of the Request. Note that the absolute path path cannot be empty; if none is present in the original URI, it MUST
cannot be empty; if none is present in the original URI, it MUST be be given as "/" (the server root).
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 section
3.2.1. If the Request-URI is encoded using the "% HEX HEX" encoding 3.2.1. If the Request-URI is encoded using the "% HEX HEX" encoding
[42], the origin server MUST decode the Request-URI in order to [42], the origin server MUST decode the Request-URI in order to
properly interpret the request. Servers SHOULD respond to invalid 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 "/".
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rewrite the Request-URI. rewrite the Request-URI.
5.2 The Resource Identified by a Request 5.2 The Resource Identified by a Request
The exact resource identified by an Internet request is determined by The exact resource identified by an Internet request is determined by
examining both the Request-URI and the Host header field. examining both the Request-URI and the Host header field.
An origin server that does not allow resources to differ by the An origin server that does not allow resources to differ by the
requested host MAY ignore the Host header field value when requested host MAY ignore the Host header field value when
determining the resource identified by an HTTP/1.1 request. (But see determining the resource identified by an HTTP/1.1 request. (But see
section 19.6.1.1 for other requirements on Host support in HTTP/1.1.) appendix F.1.1 for other requirements on Host support in HTTP/1.1.)
An origin server that does differentiate resources based on the host An origin server that does differentiate resources based on the host
requested (sometimes referred to as virtual hosts or vanity host requested (sometimes referred to as virtual hosts or vanity host
names) MUST use the following rules for determining the requested names) MUST use the following rules for determining the requested
resource on an HTTP/1.1 request: resource on an HTTP/1.1 request:
1. If Request-URI is an absoluteURI, the host is part of the 1. If Request-URI is an absoluteURI, the host is part of the
Request-URI. Any Host header field value in the request MUST be Request-URI. Any Host header field value in the request MUST be
ignored. ignored.
2. If the Request-URI is not an absoluteURI, and the request includes 2. If the Request-URI is not an absoluteURI, and the request
a Host header field, the host is determined by the Host header includes a Host header field, the host is determined by the Host
field value. header field value.
3. If the host as determined by rule 1 or 2 is not a valid host on 3. If the host as determined by rule 1 or 2 is not a valid host on
the server, the response MUST be a 400 (Bad Request) error message. the server, the response MUST be a 400 (Bad Request) error
message.
Recipients of an HTTP/1.0 request that lacks a Host header field MAY Recipients of an HTTP/1.0 request that lacks a Host header field MAY
attempt to use heuristics (e.g., examination of the URI path for attempt to use heuristics (e.g., examination of the URI path for
something unique to a particular host) in order to determine what something unique to a particular host) in order to determine what
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
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| 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 sequence. characters. No CR or LF is allowed except in the final CRLF
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.
The first digit of the Status-Code defines the class of response. The The first digit of the Status-Code defines the class of response.
last two digits do not have any categorization role. There are 5 The last two digits do not have any categorization role. There are 5
values for the first digit: values for the first digit:
- 1xx: Informational - Request received, continuing process o 1xx: Informational - Request received, continuing process
- 2xx: Success - The action was successfully received, o 2xx: Success - The action was successfully received, understood,
understood, and accepted and accepted
- 3xx: Redirection - Further action must be taken in order to o 3xx: Redirection - Further action must be taken in order to
complete the request complete the request
- 4xx: Client Error - The request contains bad syntax or cannot o 4xx: Client Error - The request contains bad syntax or cannot be
be fulfilled fulfilled
o 5xx: Server Error - The server failed to fulfill an apparently
- 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
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safely assume that there was something wrong with its request and safely assume that there was something wrong with its request and
treat the response as if it had received a 400 status code. In such treat the response as if it had received a 400 status code. In such
cases, user agents SHOULD present to the user the entity returned cases, user agents SHOULD present to the user the entity returned
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 about Line. These header fields give information about the server and
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
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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
recipient MAY attempt to guess the media type via inspection of its recipient MAY attempt to guess the media type via inspection of its
content and/or the name extension(s) of the URI used to identify the content and/or the name extension(s) of the URI used to identify the
resource. If the media type remains unknown, the recipient SHOULD resource. If the media type remains unknown, the recipient SHOULD
treat it as type "application/octet-stream". treat it as type "application/octet-stream".
7.2.2 Entity Length 7.2.2 Entity Length
The entity-length of a message is the length of the message-body The entity-length of a message is the length of the message-body
before any transfer-codings have been applied. Section 4.4 defines before any transfer-codings have been applied. section 4.4 defines
how the transfer-length of a message-body is determined. how the transfer-length of a message-body is determined.
8 Connections 8 Connections
8.1 Persistent Connections 8.1 Persistent Connections
8.1.1 Purpose 8.1.1 Purpose
Prior to persistent connections, a separate TCP connection was Prior to persistent connections, a separate TCP connection was
established to fetch each URL, increasing the load on HTTP servers established to fetch each URL, increasing the load on HTTP servers
and causing congestion on the Internet. The use of inline images and and causing congestion on the Internet. The use of inline images and
other associated data often require a client to make multiple other associated data often require a client to make multiple
requests of the same server in a short amount of time. Analysis of requests of the same server in a short amount of time. Analysis of
these performance problems and results from a prototype these performance problems and results from a prototype
implementation are available [26] [30]. Implementation experience and implementation are available [26] [30]. Implementation experience
measurements of actual HTTP/1.1 (RFC 2068) implementations show good and measurements of actual HTTP/1.1 (RFC 2068) implementations show
results [39]. Alternatives have also been explored, for example, good results [39]. Alternatives have also been explored, for
T/TCP [27]. example, T/TCP [27].
Persistent HTTP connections have a number of advantages: Persistent HTTP connections have a number of advantages:
- By opening and closing fewer TCP connections, CPU time is saved o By opening and closing fewer TCP connections, CPU time is saved in
in routers and hosts (clients, servers, proxies, gateways, routers and hosts (clients, servers, proxies, gateways, tunnels,
tunnels, or caches), and memory used for TCP protocol control or caches), and memory used for TCP protocol control blocks can be
blocks can be saved in hosts. saved in hosts.
- HTTP requests and responses can be pipelined on a connection. o HTTP requests and responses can be pipelined on a connection.
Pipelining allows a client to make multiple requests without Pipelining allows a client to make multiple requests without
waiting for each response, allowing a single TCP connection to waiting for each response, allowing a single TCP connection to be
be used much more efficiently, with much lower elapsed time. used much more efficiently, with much lower elapsed time.
- Network congestion is reduced by reducing the number of packets o Network congestion is reduced by reducing the number of packets
caused by TCP opens, and by allowing TCP sufficient time to caused by TCP opens, and by allowing TCP sufficient time to
determine the congestion state of the network. determine the congestion state of the network.
- Latency on subsequent requests is reduced since there is no time o Latency on subsequent requests is reduced since there is no time
spent in TCP's connection opening handshake. spent in TCP's connection opening handshake.
- HTTP can evolve more gracefully, since errors can be reported o HTTP can evolve more gracefully, since errors can be reported
without the penalty of closing the TCP connection. Clients using without the penalty of closing the TCP connection. Clients using
future versions of HTTP might optimistically try a new feature, future versions of HTTP might optimistically try a new feature,
but if communicating with an older server, retry with old but if communicating with an older server, retry with old
semantics after an error is reported. semantics after an error is reported.
HTTP implementations SHOULD implement persistent connections. HTTP implementations SHOULD implement persistent connections.
8.1.2 Overall Operation 8.1.2 Overall Operation
A significant difference between HTTP/1.1 and earlier versions of A significant difference between HTTP/1.1 and earlier versions of
HTTP is that persistent connections are the default behavior of any HTTP is that persistent connections are the default behavior of any
HTTP connection. That is, unless otherwise indicated, the client HTTP connection. That is, unless otherwise indicated, the client
SHOULD assume that the server will maintain a persistent connection, SHOULD assume that the server will maintain a persistent connection,
even after error responses from the server. even after error responses from the server.
Persistent connections provide a mechanism by which a client and a Persistent connections provide a mechanism by which a client and a
server can signal the close of a TCP connection. This signaling takes server can signal the close of a TCP connection. This signaling
place using the Connection header field (section 14.10). Once a close takes place using the Connection header field (section 14.10). Once
has been signaled, the client MUST NOT send any more requests on that a close has been signaled, the client MUST NOT send any more requests
connection. on that connection.
8.1.2.1 Negotiation 8.1.2.1 Negotiation
An HTTP/1.1 server MAY assume that a HTTP/1.1 client intends to An HTTP/1.1 server MAY assume that a HTTP/1.1 client intends to
maintain a persistent connection unless a Connection header including maintain a persistent connection unless a Connection header including
the connection-token "close" was sent in the request. If the server the connection-token "close" was sent in the request. If the server
chooses to close the connection immediately after sending the chooses to close the connection immediately after sending the
response, it SHOULD send a Connection header including the response, it SHOULD send a Connection header including the
connection-token close. connection-token close.
An HTTP/1.1 client MAY expect a connection to remain open, but would An HTTP/1.1 client MAY expect a connection to remain open, but would
decide to keep it open based on whether the response from a server decide to keep it open based on whether the response from a server
contains a Connection header with the connection-token close. In case contains a Connection header with the connection-token close. In
the client does not want to maintain a connection for more than that case the client does not want to maintain a connection for more than
request, it SHOULD send a Connection header including the that request, it SHOULD send a Connection header including the
connection-token close. connection-token close.
If either the client or the server sends the close token in the If either the client or the server sends the close token in the
Connection header, that request becomes the last one for the Connection header, that request becomes the last one for the
connection. connection.
Clients and servers SHOULD NOT assume that a persistent connection is Clients and servers SHOULD NOT assume that a persistent connection is
maintained for HTTP versions less than 1.1 unless it is explicitly maintained for HTTP versions less than 1.1 unless it is explicitly
signaled. See section 19.6.2 for more information on backward signaled. See appendix F.2 for more information on backward
compatibility with HTTP/1.0 clients. compatibility with HTTP/1.0 clients.
In order to remain persistent, all messages on the connection MUST In order to remain persistent, all messages on the connection MUST
have a self-defined message length (i.e., one not defined by closure have a self-defined message length (i.e., one not defined by closure
of the connection), as described in section 4.4. of the connection), as described in section 4.4.
8.1.2.2 Pipelining 8.1.2.2 Pipelining
A client that supports persistent connections MAY "pipeline" its A client that supports persistent connections MAY "pipeline" its
requests (i.e., send multiple requests without waiting for each requests (i.e., send multiple requests without waiting for each
response). A server MUST send its responses to those requests in the response). A server MUST send its responses to those requests in the
same order that the requests were received. same order that the requests were received.
Clients which assume persistent connections and pipeline immediately Clients which assume persistent connections and pipeline immediately
after connection establishment SHOULD be prepared to retry their after connection establishment SHOULD be prepared to retry their
connection if the first pipelined attempt fails. If a client does connection if the first pipelined attempt fails. If a client does
such a retry, it MUST NOT pipeline before it knows the connection is such a retry, it MUST NOT pipeline before it knows the connection is
persistent. Clients MUST also be prepared to resend their requests if persistent. Clients MUST also be prepared to resend their requests
the server closes the connection before sending all of the if the server closes the connection before sending all of the
corresponding responses. corresponding responses.
Clients SHOULD NOT pipeline requests using non-idempotent methods or Clients SHOULD NOT pipeline requests using non-idempotent methods or
non-idempotent sequences of methods (see section 9.1.2). Otherwise, a non-idempotent sequences of methods (see section 9.1.2). Otherwise,
premature termination of the transport connection could lead to a premature termination of the transport connection could lead to
indeterminate results. A client wishing to send a non-idempotent indeterminate results. A client wishing to send a non-idempotent
request SHOULD wait to send that request until it has received the request SHOULD wait to send that request until it has received the
response status for the previous request. response status for the previous request.
8.1.3 Proxy Servers 8.1.3 Proxy Servers
It is especially important that proxies correctly implement the It is especially important that proxies correctly implement the
properties of the Connection header field as specified in section properties of the Connection header field as specified in
14.10. section 14.10.
The proxy server MUST signal persistent connections separately with The proxy server MUST signal persistent connections separately with
its clients and the origin servers (or other proxy servers) that it its clients and the origin servers (or other proxy servers) that it
connects to. Each persistent connection applies to only one transport connects to. Each persistent connection applies to only one
link. transport link.
A proxy server MUST NOT establish a HTTP/1.1 persistent connection A proxy server MUST NOT establish a HTTP/1.1 persistent connection
with an HTTP/1.0 client (but see RFC 2068 [33] for information and with an HTTP/1.0 client (but see RFC 2068 [33] for information and
discussion of the problems with the Keep-Alive header implemented by discussion of the problems with the Keep-Alive header implemented by
many HTTP/1.0 clients). many HTTP/1.0 clients).
8.1.4 Practical Considerations 8.1.4 Practical Considerations
Servers will usually have some time-out value beyond which they will Servers will usually have some time-out value beyond which they will
no longer maintain an inactive connection. Proxy servers might make no longer maintain an inactive connection. Proxy servers might make
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connection. From the server's point of view, the connection is being connection. From the server's point of view, the connection is being
closed while it was idle, but from the client's point of view, a closed while it was idle, but from the client's point of view, a
request is in progress. request is in progress.
This means that clients, servers, and proxies MUST be able to recover This means that clients, servers, and proxies MUST be able to recover
from asynchronous close events. Client software SHOULD reopen the from asynchronous close events. Client software SHOULD reopen the
transport connection and retransmit the aborted sequence of requests transport connection and retransmit the aborted sequence of requests
without user interaction so long as the request sequence is without user interaction so long as the request sequence is
idempotent (see section 9.1.2). Non-idempotent methods or sequences idempotent (see section 9.1.2). Non-idempotent methods or sequences
MUST NOT be automatically retried, although user agents MAY offer a MUST NOT be automatically retried, although user agents MAY offer a
human operator the choice of retrying the request(s). Confirmation by human operator the choice of retrying the request(s). Confirmation
user-agent software with semantic understanding of the application by user-agent software with semantic understanding of the application
MAY substitute for user confirmation. The automatic retry SHOULD NOT MAY substitute for user confirmation. The automatic retry SHOULD NOT
be repeated if the second sequence of requests fails. be repeated if the second sequence of requests fails.
Servers SHOULD always respond to at least one request per connection, Servers SHOULD always respond to at least one request per connection,
if at all possible. Servers SHOULD NOT close a connection in the if at all possible. Servers SHOULD NOT close a connection in the
middle of transmitting a response, unless a network or client failure middle of transmitting a response, unless a network or client failure
is suspected. is suspected.
Clients that use persistent connections SHOULD limit the number of Clients that use persistent connections SHOULD limit the number of
simultaneous connections that they maintain to a given server. A simultaneous connections that they maintain to a given server. A
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The purpose of the 100 (Continue) status (see section 10.1.1) is to The purpose of the 100 (Continue) status (see section 10.1.1) is to
allow a client that is sending a request message with a request body allow a client that is sending a request message with a request body
to determine if the origin server is willing to accept the request to determine if the origin server is willing to accept the request
(based on the request headers) before the client sends the request (based on the request headers) before the client sends the request
body. In some cases, it might either be inappropriate or highly body. In some cases, it might either be inappropriate or highly
inefficient for the client to send the body if the server will reject inefficient for the client to send the body if the server will reject
the message without looking at the body. the message without looking at the body.
Requirements for HTTP/1.1 clients: Requirements for HTTP/1.1 clients:
- If a client will wait for a 100 (Continue) response before o If a client will wait for a 100 (Continue) response before sending
sending the request body, it MUST send an Expect request-header the request body, it MUST send an Expect request-header field
field (section 14.20) with the "100-continue" expectation. (section 14.20) with the "100-continue" expectation.
- A client MUST NOT send an Expect request-header field (section o A client MUST NOT send an Expect request-header field
14.20) with the "100-continue" expectation if it does not intend (section 14.20) with the "100-continue" expectation if it does not
to send a request body. intend to send a request body.
Because of the presence of older implementations, the protocol allows Because of the presence of older implementations, the protocol allows
ambiguous situations in which a client may send "Expect: 100- ambiguous situations in which a client may send "Expect: 100-
continue" without receiving either a 417 (Expectation Failed) status continue" without receiving either a 417 (Expectation Failed) status
or a 100 (Continue) status. Therefore, when a client sends this or a 100 (Continue) status. Therefore, when a client sends this
header field to an origin server (possibly via a proxy) from which it header field to an origin server (possibly via a proxy) from which it
has never seen a 100 (Continue) status, the client SHOULD NOT wait has never seen a 100 (Continue) status, the client SHOULD NOT wait
for an indefinite period before sending the request body. for an indefinite period before sending the request body.
Requirements for HTTP/1.1 origin servers: Requirements for HTTP/1.1 origin servers:
- Upon receiving a request which includes an Expect request-header o Upon receiving a request which includes an Expect request-header
field with the "100-continue" expectation, an origin server MUST field with the "100-continue" expectation, an origin server MUST
either respond with 100 (Continue) status and continue to read either respond with 100 (Continue) status and continue to read
from the input stream, or respond with a final status code. The from the input stream, or respond with a final status code. The
origin server MUST NOT wait for the request body before sending origin server MUST NOT wait for the request body before sending
the 100 (Continue) response. If it responds with a final status the 100 (Continue) response. If it responds with a final status
code, it MAY close the transport connection or it MAY continue code, it MAY close the transport connection or it MAY continue to
to read and discard the rest of the request. It MUST NOT read and discard the rest of the request. It MUST NOT perform the
perform the requested method if it returns a final status code. requested method if it returns a final status code.
- An origin server SHOULD NOT send a 100 (Continue) response if o An origin server SHOULD NOT send a 100 (Continue) response if the
the request message does not include an Expect request-header request message does not include an Expect request-header field
field with the "100-continue" expectation, and MUST NOT send a with the "100-continue" expectation, and MUST NOT send a 100
100 (Continue) response if such a request comes from an HTTP/1.0 (Continue) response if such a request comes from an HTTP/1.0 (or
(or earlier) client. There is an exception to this rule: for earlier) client. There is an exception to this rule: for
compatibility with RFC 2068, a server MAY send a 100 (Continue) compatibility with RFC 2068, a server MAY send a 100 (Continue)
status in response to an HTTP/1.1 PUT or POST request that does status in response to an HTTP/1.1 PUT or POST request that does
not include an Expect request-header field with the "100- not include an Expect request-header field with the "100-continue"
continue" expectation. This exception, the purpose of which is expectation. This exception, the purpose of which is to minimize
to minimize any client processing delays associated with an any client processing delays associated with an undeclared wait
undeclared wait for 100 (Continue) status, applies only to for 100 (Continue) status, applies only to HTTP/1.1 requests, and
HTTP/1.1 requests, and not to requests with any other HTTP- not to requests with any other HTTP-version value.
version value.
- An origin server MAY omit a 100 (Continue) response if it has o An origin server MAY omit a 100 (Continue) response if it has
already received some or all of the request body for the already received some or all of the request body for the
corresponding request. corresponding request.
- An origin server that sends a 100 (Continue) response MUST o An origin server that sends a 100 (Continue) response MUST
ultimately send a final status code, once the request body is ultimately send a final status code, once the request body is
received and processed, unless it terminates the transport received and processed, unless it terminates the transport
connection prematurely. connection prematurely.
- If an origin server receives a request that does not include an o If an origin server receives a request that does not include an
Expect request-header field with the "100-continue" expectation, Expect request-header field with the "100-continue" expectation,
the request includes a request body, and the server responds the request includes a request body, and the server responds with
with a final status code before reading the entire request body a final status code before reading the entire request body from
from the transport connection, then the server SHOULD NOT close the transport connection, then the server SHOULD NOT close the
the transport connection until it has read the entire request, transport connection until it has read the entire request, or
or until the client closes the connection. Otherwise, the client until the client closes the connection. Otherwise, the client
might not reliably receive the response message. However, this might not reliably receive the response message. However, this
requirement is not be construed as preventing a server from requirement is not be construed as preventing a server from
defending itself against denial-of-service attacks, or from defending itself against denial-of-service attacks, or from badly
badly broken client implementations. broken client implementations.
Requirements for HTTP/1.1 proxies: Requirements for HTTP/1.1 proxies:
- If a proxy receives a request that includes an Expect request- o If a proxy receives a request that includes an Expect request-
header field with the "100-continue" expectation, and the proxy header field with the "100-continue" expectation, and the proxy
either knows that the next-hop server complies with HTTP/1.1 or either knows that the next-hop server complies with HTTP/1.1 or
higher, or does not know the HTTP version of the next-hop higher, or does not know the HTTP version of the next-hop server,
server, it MUST forward the request, including the Expect header it MUST forward the request, including the Expect header field.
field.
- If the proxy knows that the version of the next-hop server is o If the proxy knows that the version of the next-hop server is
HTTP/1.0 or lower, it MUST NOT forward the request, and it MUST HTTP/1.0 or lower, it MUST NOT forward the request, and it MUST
respond with a 417 (Expectation Failed) status. respond with a 417 (Expectation Failed) status.
- Proxies SHOULD maintain a cache recording the HTTP version o Proxies SHOULD maintain a cache recording the HTTP version numbers
numbers received from recently-referenced next-hop servers. received from recently-referenced next-hop servers.
- A proxy MUST NOT forward a 100 (Continue) response if the o A proxy MUST NOT forward a 100 (Continue) response if the request
request message was received from an HTTP/1.0 (or earlier) message was received from an HTTP/1.0 (or earlier) client and did
client and did not include an Expect request-header field with not include an Expect request-header field with the "100-continue"
the "100-continue" expectation. This requirement overrides the expectation. This requirement overrides the general rule for
general rule for forwarding of 1xx responses (see section 10.1). forwarding of 1xx responses (see section 10.1).
8.2.4 Client Behavior if Server Prematurely Closes Connection 8.2.4 Client Behavior if Server Prematurely Closes Connection
If an HTTP/1.1 client sends a request which includes a request body, If an HTTP/1.1 client sends a request which includes a request body,
but which does not include an Expect request-header field with the but which does not include an Expect request-header field with the
"100-continue" expectation, and if the client is not directly "100-continue" expectation, and if the client is not directly
connected to an HTTP/1.1 origin server, and if the client sees the connected to an HTTP/1.1 origin server, and if the client sees the
connection close before receiving any status from the server, the connection close before receiving any status from the server, the
client SHOULD retry the request. If the client does retry this client SHOULD retry the request. If the client does retry this
request, it MAY use the following "binary exponential backoff" request, it MAY use the following "binary exponential backoff"
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1. Initiate a new connection to the server 1. Initiate a new connection to the server
2. Transmit the request-headers 2. Transmit the request-headers
3. Initialize a variable R to the estimated round-trip time to the 3. Initialize a variable R to the estimated round-trip time to the
server (e.g., based on the time it took to establish the server (e.g., based on the time it took to establish the
connection), or to a constant value of 5 seconds if the round- connection), or to a constant value of 5 seconds if the round-
trip time is not available. trip time is not available.
4. Compute T = R * (2**N), where N is the number of previous 4. Compute T = R * (2**N), where N is the number of previous retries
retries of this request. of this request.
5. Wait either for an error response from the server, or for T 5. Wait either for an error response from the server, or for T
seconds (whichever comes first) seconds (whichever comes first)
6. If no error response is received, after T seconds transmit the 6. If no error response is received, after T seconds transmit the
body of the request. body of the request.
7. If client sees that the connection is closed prematurely, 7. If client sees that the connection is closed prematurely, repeat
repeat from step 1 until the request is accepted, an error from step 1 until the request is accepted, an error response is
response is received, or the user becomes impatient and received, or the user becomes impatient and terminates the retry
terminates the retry process. process.
If at any point an error status is received, the client If at any point an error status is received, the client
- SHOULD NOT continue and o SHOULD NOT continue and
- SHOULD close the connection if it has not completed sending the o SHOULD close the connection if it has not completed sending the
request message. request message.
9 Method Definitions 9 Method Definitions
The set of common methods for HTTP/1.1 is defined below. Although The set of common methods for HTTP/1.1 is defined below. Although
this set can be expanded, additional methods cannot be assumed to this set can be expanded, additional methods cannot be assumed to
share the same semantics for separately extended clients and servers. share the same semantics for separately extended clients and servers.
The Host request-header field (section 14.23) MUST accompany all The Host request-header field (section 14.23) MUST accompany all
HTTP/1.1 requests. HTTP/1.1 requests.
9.1 Safe and Idempotent Methods 9.1 Safe and Idempotent Methods
9.1.1 Safe Methods 9.1.1 Safe Methods
Implementors should be aware that the software represents the user in Implementors should be aware that the software represents the user in
their interactions over the Internet, and should be careful to allow their interactions over the Internet, and should be careful to allow
the user to be aware of any actions they might take which may have an the user to be aware of any actions they might take which may have an
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specification does not define any use for such a body, future specification does not define any use for such a body, future
extensions to HTTP might use the OPTIONS body to make more detailed extensions to HTTP might use the OPTIONS body to make more detailed
queries on the server. A server that does not support such an queries on the server. A server that does not support such an
extension MAY discard the request body. extension MAY discard the request body.
If the Request-URI is an asterisk ("*"), the OPTIONS request is If the Request-URI is an asterisk ("*"), the OPTIONS request is
intended to apply to the server in general rather than to a specific intended to apply to the server in general rather than to a specific
resource. Since a server's communication options typically depend on resource. Since a server's communication options typically depend on
the resource, the "*" request is only useful as a "ping" or "no-op" the resource, the "*" request is only useful as a "ping" or "no-op"
type of method; it does nothing beyond allowing the client to test type of method; it does nothing beyond allowing the client to test
the capabilities of the server. For example, this can be used to test the capabilities of the server. For example, this can be used to
a proxy for HTTP/1.1 compliance (or lack thereof). test a proxy for HTTP/1.1 compliance (or lack thereof).
If the Request-URI is not an asterisk, the OPTIONS request applies If the Request-URI is not an asterisk, the OPTIONS request applies
only to the options that are available when communicating with that only to the options that are available when communicating with that
resource. resource.
A 200 response SHOULD include any header fields that indicate A 200 response SHOULD include any header fields that indicate
optional features implemented by the server and applicable to that optional features implemented by the server and applicable to that
resource (e.g., Allow), possibly including extensions not defined by resource (e.g., Allow), possibly including extensions not defined by
this specification. The response body, if any, SHOULD also include this specification. The response body, if any, SHOULD also include
information about the communication options. The format for such a information about the communication options. The format for such a
body is not defined by this specification, but might be defined by body is not defined by this specification, but might be defined by
future extensions to HTTP. Content negotiation MAY be used to select future extensions to HTTP. Content negotiation MAY be used to select
the appropriate response format. If no response body is included, the the appropriate response format. If no response body is included,
response MUST include a Content-Length field with a field-value of the response MUST include a Content-Length field with a field-value
"0". of "0".
The Max-Forwards request-header field MAY be used to target a The Max-Forwards request-header field MAY be used to target a
specific proxy in the request chain. When a proxy receives an OPTIONS specific proxy in the request chain. When a proxy receives an
request on an absoluteURI for which request forwarding is permitted, OPTIONS request on an absoluteURI for which request forwarding is
the proxy MUST check for a Max-Forwards field. If the Max-Forwards permitted, the proxy MUST check for a Max-Forwards field. If the
field-value is zero ("0"), the proxy MUST NOT forward the message; Max-Forwards field-value is zero ("0"), the proxy MUST NOT forward
instead, the proxy SHOULD respond with its own communication options. the message; instead, the proxy SHOULD respond with its own
If the Max-Forwards field-value is an integer greater than zero, the communication options. If the Max-Forwards field-value is an integer
proxy MUST decrement the field-value when it forwards the request. If greater than zero, the proxy MUST decrement the field-value when it
no Max-Forwards field is present in the request, then the forwarded forwards the request. If no Max-Forwards field is present in the
request MUST NOT include a Max-Forwards field. request, then the forwarded request MUST NOT include a Max-Forwards
field.
9.3 GET 9.3 GET
The GET method means retrieve whatever information (in the form of an The GET method means retrieve whatever information (in the form of an
entity) is identified by the Request-URI. If the Request-URI refers entity) is identified by the Request-URI. If the Request-URI refers
to a data-producing process, it is the produced data which shall be to a data-producing process, it is the produced data which shall be
returned as the entity in the response and not the source text of the returned as the entity in the response and not the source text of the
process, unless that text happens to be the output of the process. process, unless that text happens to be the output of the process.
The semantics of the GET method change to a "conditional GET" if the The semantics of the GET method change to a "conditional GET" if the
request message includes an If-Modified-Since, If-Unmodified-Since, request message includes an If-Modified-Since, If-Unmodified-Since,
If-Match, If-None-Match, or If-Range header field. A conditional GET If-Match, If-None-Match, or If-Range header field. A conditional GET
method requests that the entity be transferred only under the method requests that the entity be transferred only under the
circumstances described by the conditional header field(s). The circumstances described by the conditional header field(s). The
conditional GET method is intended to reduce unnecessary network conditional GET method is intended to reduce unnecessary network
usage by allowing cached entities to be refreshed without requiring usage by allowing cached entities to be refreshed without requiring
multiple requests or transferring data already held by the client. multiple requests or transferring data already held by the client.
The semantics of the GET method change to a "partial GET" if the The semantics of the GET method change to a "partial GET" if the
request message includes a Range header field. A partial GET requests request message includes a Range header field. A partial GET
that only part of the entity be transferred, as described in section requests that only part of the entity be transferred, as described in
14.35. The partial GET method is intended to reduce unnecessary section 14.35. The partial GET method is intended to reduce
network usage by allowing partially-retrieved entities to be unnecessary network usage by allowing partially-retrieved entities to
completed without transferring data already held by the client. be completed without transferring data already held by the client.
The response to a GET request is cacheable if and only if it meets The response to a GET request is cacheable if and only if it meets
the requirements for HTTP caching described in section 13. the requirements for HTTP caching described in section 13.
See section 15.1.3 for security considerations when used for forms. See section 15.1.3 for security considerations when used for forms.
9.4 HEAD 9.4 HEAD
The HEAD method is identical to GET except that the server MUST NOT The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metainformation contained return a message-body in the response. The metainformation contained
in the HTTP headers in response to a HEAD request SHOULD be identical in the HTTP headers in response to a HEAD request SHOULD be identical
to the information sent in response to a GET request. This method can to the information sent in response to a GET request. This method
be used for obtaining metainformation about the entity implied by the can be used for obtaining metainformation about the entity implied by
request without transferring the entity-body itself. This method is the request without transferring the entity-body itself. This method
often used for testing hypertext links for validity, accessibility, is often used for testing hypertext links for validity,
and recent modification. accessibility, and recent modification.
The response to a HEAD request MAY be cacheable in the sense that the The response to a HEAD request MAY be cacheable in the sense that the
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 a new subordinate of the resource
identified by the Request-URI in the Request-Line. POST is designed identified by the Request-URI in the Request-Line. POST is designed
to allow a uniform method to cover the following functions: to allow a uniform method to cover the following functions:
- Annotation of existing resources; o Annotation of existing resources;
- Posting a message to a bulletin board, newsgroup, mailing list, o Posting a message to a bulletin board, newsgroup, mailing list, or
or similar group of articles; similar group of articles;
- 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;
- 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 entity server and is usually dependent on the Request-URI. The posted
is subordinate to that URI in the same way that a file is subordinate entity is subordinate to that URI in the same way that a file is
to a directory containing it, a news article is subordinate to a subordinate to a directory containing it, a news article is
newsgroup to which it is posted, or a record is subordinate to a subordinate to a newsgroup to which it is posted, or a record is
database. 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
header (see section 14.30). header (see section 14.30).
Responses to this method are not cacheable, unless the response Responses to this method are not cacheable, unless the response
includes appropriate Cache-Control or Expires header fields. However, includes appropriate Cache-Control or Expires header fields.
the 303 (See Other) response can be used to direct the user agent to However, the 303 (See Other) response can be used to direct the user
retrieve a cacheable resource. agent to retrieve a cacheable resource.
POST requests MUST obey the message transmission requirements set out POST requests MUST obey the message transmission requirements set out
in section 8.2. in section 8.2.
See section 15.1.3 for security considerations. See section 15.1.3 for security considerations.
9.6 PUT 9.6 PUT
The PUT method requests that the enclosed entity be stored under the The PUT method requests that the enclosed entity be stored under the
supplied Request-URI. If the Request-URI refers to an already supplied Request-URI. If the Request-URI refers to an already
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Request-URI does not point to an existing resource, and that URI is Request-URI does not point to an existing resource, and that URI is
capable of being defined as a new resource by the requesting user capable of being defined as a new resource by the requesting user
agent, the origin server can create the resource with that URI. If a agent, the origin server can create the resource with that URI. If a
new resource is created, the origin server MUST inform the user agent new resource is created, the origin server MUST inform the user agent
via the 201 (Created) response. If an existing resource is modified, via the 201 (Created) response. If an existing resource is modified,
either the 200 (OK) or 204 (No Content) response codes SHOULD be sent either the 200 (OK) or 204 (No Content) response codes SHOULD be sent
to indicate successful completion of the request. If the resource to indicate successful completion of the request. If the resource
could not be created or modified with the Request-URI, an appropriate could not be created or modified with the Request-URI, an appropriate
error response SHOULD be given that reflects the nature of the error response SHOULD be given that reflects the nature of the
problem. The recipient of the entity MUST NOT ignore any Content-* problem. The recipient of the entity MUST NOT ignore any Content-*
(e.g. Content-Range) headers that it does not understand or implement (e.g. Content-Range) headers that it does not understand or
and MUST return a 501 (Not Implemented) response in such cases. implement and MUST return a 501 (Not Implemented) response in such
cases.
If the request passes through a cache and the Request-URI identifies If the request passes through a cache and the Request-URI identifies
one or more currently cached entities, those entries SHOULD be one or more currently cached entities, those entries SHOULD be
treated as stale. Responses to this method are not cacheable. treated as stale. Responses to this method are not cacheable.
The fundamental difference between the POST and PUT requests is The fundamental difference between the POST and PUT requests is
reflected in the different meaning of the Request-URI. The URI in a reflected in the different meaning of the Request-URI. The URI in a
POST request identifies the resource that will handle the enclosed POST request identifies the resource that will handle the enclosed
entity. That resource might be a data-accepting process, a gateway to entity. That resource might be a data-accepting process, a gateway
some other protocol, or a separate entity that accepts annotations. to some other protocol, or a separate entity that accepts
In contrast, the URI in a PUT request identifies the entity enclosed annotations. In contrast, the URI in a PUT request identifies the
with the request -- the user agent knows what URI is intended and the entity enclosed with the request -- the user agent knows what URI is
server MUST NOT attempt to apply the request to some other resource. intended and the server MUST NOT attempt to apply the request to some
If the server desires that the request be applied to a different URI, other resource. If the server desires that the request be applied to
it MUST send a 301 (Moved Permanently) response; the user agent MAY a different URI, it MUST send a 301 (Moved Permanently) response; the
then make its own decision regarding whether or not to redirect the user agent MAY then make its own decision regarding whether or not to
request. redirect the request.
A single resource MAY be identified by many different URIs. For A single resource MAY be identified by many different URIs. For
example, an article might have a URI for identifying "the current example, an article might have a URI for identifying "the current
version" which is separate from the URI identifying each particular version" which is separate from the URI identifying each particular
version. In this case, a PUT request on a general URI might result in version. In this case, a PUT request on a general URI might result
several other URIs being defined by the origin server. in several other URIs being defined by the origin server.
HTTP/1.1 does not define how a PUT method affects the state of an HTTP/1.1 does not define how a PUT method affects the state of an
origin server. origin server.
PUT requests MUST obey the message transmission requirements set out PUT requests MUST obey the message transmission requirements set out
in section 8.2. in section 8.2.
Unless otherwise specified for a particular entity-header, the Unless otherwise specified for a particular entity-header, the
entity-headers in the PUT request SHOULD be applied to the resource entity-headers in the PUT request SHOULD be applied to the resource
created or modified by the PUT. created or modified by the PUT.
9.7 DELETE 9.7 DELETE
The DELETE method requests that the origin server delete the resource The DELETE method requests that the origin server delete the resource
identified by the Request-URI. This method MAY be overridden by human identified by the Request-URI. This method MAY be overridden by
intervention (or other means) on the origin server. The client cannot human intervention (or other means) on the origin server. The client
be guaranteed that the operation has been carried out, even if the cannot be guaranteed that the operation has been carried out, even if
status code returned from the origin server indicates that the action the status code returned from the origin server indicates that the
has been completed successfully. However, the server SHOULD NOT action has been completed successfully. However, the server SHOULD
indicate success unless, at the time the response is given, it NOT indicate success unless, at the time the response is given, it
intends to delete the resource or move it to an inaccessible intends to delete the resource or move it to