source: draft-ietf-httpbis/latest/p2-semantics.xml @ 333

Last change on this file since 333 was 333, checked in by julian.reschke@…, 14 years ago

Resolve #103: explain shorthand notation "Content-*" (closes #103).

  • Property svn:eol-style set to native
File size: 141.9 KB
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "November">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY messaging                  "<xref target='Part1' xmlns:x=''/>">
18  <!ENTITY payload                    "<xref target='Part3' xmlns:x=''/>">
19  <!ENTITY conditional                "<xref target='Part4' xmlns:x=''/>">
20  <!ENTITY range                      "<xref target='Part5' xmlns:x=''/>">
21  <!ENTITY caching                    "<xref target='Part6' xmlns:x=''/>">
22  <!ENTITY auth                       "<xref target='Part7' xmlns:x=''/>">
23  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x=''/>">
24  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
25  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
26  <!ENTITY general-syntax             "<xref target='Part1' x:rel='#general.syntax' xmlns:x=''/>">
27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
28  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
29  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
63  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
65<?rfc toc="yes" ?>
66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
76<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
77     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
78     xmlns:x=''
79     xmlns:rdf=''>
82  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
84  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
85    <organization abbrev="Day Software">Day Software</organization>
86    <address>
87      <postal>
88        <street>23 Corporate Plaza DR, Suite 280</street>
89        <city>Newport Beach</city>
90        <region>CA</region>
91        <code>92660</code>
92        <country>USA</country>
93      </postal>
94      <phone>+1-949-706-5300</phone>
95      <facsimile>+1-949-706-5305</facsimile>
96      <email></email>
97      <uri></uri>
98    </address>
99  </author>
101  <author initials="J." surname="Gettys" fullname="Jim Gettys">
102    <organization>One Laptop per Child</organization>
103    <address>
104      <postal>
105        <street>21 Oak Knoll Road</street>
106        <city>Carlisle</city>
107        <region>MA</region>
108        <code>01741</code>
109        <country>USA</country>
110      </postal>
111      <email></email>
112      <uri></uri>
113    </address>
114  </author>
116  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
117    <organization abbrev="HP">Hewlett-Packard Company</organization>
118    <address>
119      <postal>
120        <street>HP Labs, Large Scale Systems Group</street>
121        <street>1501 Page Mill Road, MS 1177</street>
122        <city>Palo Alto</city>
123        <region>CA</region>
124        <code>94304</code>
125        <country>USA</country>
126      </postal>
127      <email></email>
128    </address>
129  </author>
131  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
132    <organization abbrev="Microsoft">Microsoft Corporation</organization>
133    <address>
134      <postal>
135        <street>1 Microsoft Way</street>
136        <city>Redmond</city>
137        <region>WA</region>
138        <code>98052</code>
139        <country>USA</country>
140      </postal>
141      <email></email>
142    </address>
143  </author>
145  <author initials="L." surname="Masinter" fullname="Larry Masinter">
146    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
147    <address>
148      <postal>
149        <street>345 Park Ave</street>
150        <city>San Jose</city>
151        <region>CA</region>
152        <code>95110</code>
153        <country>USA</country>
154      </postal>
155      <email></email>
156      <uri></uri>
157    </address>
158  </author>
160  <author initials="P." surname="Leach" fullname="Paul J. Leach">
161    <organization abbrev="Microsoft">Microsoft Corporation</organization>
162    <address>
163      <postal>
164        <street>1 Microsoft Way</street>
165        <city>Redmond</city>
166        <region>WA</region>
167        <code>98052</code>
168      </postal>
169      <email></email>
170    </address>
171  </author>
173  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
174    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
175    <address>
176      <postal>
177        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
178        <street>The Stata Center, Building 32</street>
179        <street>32 Vassar Street</street>
180        <city>Cambridge</city>
181        <region>MA</region>
182        <code>02139</code>
183        <country>USA</country>
184      </postal>
185      <email></email>
186      <uri></uri>
187    </address>
188  </author>
190  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
191    <organization abbrev="W3C">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>W3C / ERCIM</street>
195        <street>2004, rte des Lucioles</street>
196        <city>Sophia-Antipolis</city>
197        <region>AM</region>
198        <code>06902</code>
199        <country>France</country>
200      </postal>
201      <email></email>
202      <uri></uri>
203    </address>
204  </author>
206  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
207    <organization abbrev="greenbytes">greenbytes GmbH</organization>
208    <address>
209      <postal>
210        <street>Hafenweg 16</street>
211        <city>Muenster</city><region>NW</region><code>48155</code>
212        <country>Germany</country>
213      </postal>
214      <phone>+49 251 2807760</phone>   
215      <facsimile>+49 251 2807761</facsimile>   
216      <email></email>       
217      <uri></uri>     
218    </address>
219  </author>
221  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
225   The Hypertext Transfer Protocol (HTTP) is an application-level
226   protocol for distributed, collaborative, hypermedia information
227   systems. HTTP has been in use by the World Wide Web global information
228   initiative since 1990. This document is Part 2 of the seven-part specification
229   that defines the protocol referred to as "HTTP/1.1" and, taken together,
230   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
231   as expressed by request methods, request-header fields, response status codes,
232   and response-header fields.
236<note title="Editorial Note (To be removed by RFC Editor)">
237  <t>
238    Discussion of this draft should take place on the HTTPBIS working group
239    mailing list ( The current issues list is
240    at <eref target=""/>
241    and related documents (including fancy diffs) can be found at
242    <eref target=""/>.
243  </t>
244  <t>
245    The changes in this draft are summarized in <xref target="changes.since.02"/>.
246  </t>
250<section title="Introduction" anchor="introduction">
252   This document defines HTTP/1.1 request and response semantics.  Each HTTP
253   message, as defined in &messaging;, is in the form of either a request or
254   a response.  An HTTP server listens on a connection for HTTP requests and
255   responds to each request, in the order received on that connection, with
256   one or more HTTP response messages.  This document defines the commonly
257   agreed upon semantics of the HTTP uniform interface, the intentions defined
258   by each request method, and the various response messages that might be
259   expected as a result of applying that method for the requested resource.
262   This document is currently disorganized in order to minimize the changes
263   between drafts and enable reviewers to see the smaller errata changes.
264   The next draft will reorganize the sections to better reflect the content.
265   In particular, the sections will be ordered according to the typical
266   processing of an HTTP request message (after message parsing): resource
267   mapping, general header fields, methods, request modifiers, response
268   status, and resource metadata.  The current mess reflects how widely
269   dispersed these topics and associated requirements had become in
270   <xref target="RFC2616"/>.
273<section title="Requirements" anchor="intro.requirements">
275   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
276   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
277   document are to be interpreted as described in <xref target="RFC2119"/>.
280   An implementation is not compliant if it fails to satisfy one or more
281   of the &MUST; or &REQUIRED; level requirements for the protocols it
282   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
283   level and all the &SHOULD; level requirements for its protocols is said
284   to be "unconditionally compliant"; one that satisfies all the &MUST;
285   level requirements but not all the &SHOULD; level requirements for its
286   protocols is said to be "conditionally compliant."
291<section title="Notational Conventions and Generic Grammar" anchor="notation">
292  <x:anchor-alias value="comment"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="quoted-string"/>
295  <x:anchor-alias value="token"/>
297  This specification uses the ABNF syntax defined in &notation-abnf; and
298  the core rules defined in &basic-rules;:
299  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
300  <eref target=""/>.</cref>
302<figure><artwork type="abnf2616">
303  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
305<figure><artwork type="abnf2616">
306  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
307  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
308  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
310<t anchor="abnf.dependencies">
311  <x:anchor-alias value="absoluteURI"/>
312  <x:anchor-alias value="Accept"/>
313  <x:anchor-alias value="Accept-Charset"/>
314  <x:anchor-alias value="Accept-Encoding"/>
315  <x:anchor-alias value="Accept-Language"/>
316  <x:anchor-alias value="Accept-Ranges"/>
317  <x:anchor-alias value="Age"/>
318  <x:anchor-alias value="Authorization"/>
319  <x:anchor-alias value="ETag"/>
320  <x:anchor-alias value="fragment"/>
321  <x:anchor-alias value="Host"/>
322  <x:anchor-alias value="HTTP-date"/>
323  <x:anchor-alias value="If-Match"/>
324  <x:anchor-alias value="If-Modified-Since"/>
325  <x:anchor-alias value="If-None-Match"/>
326  <x:anchor-alias value="If-Range"/>
327  <x:anchor-alias value="If-Unmodified-Since"/>
328  <x:anchor-alias value="product"/>
329  <x:anchor-alias value="Proxy-Authenticate"/>
330  <x:anchor-alias value="Proxy-Authorization"/>
331  <x:anchor-alias value="Range"/>
332  <x:anchor-alias value="relativeURI"/>
333  <x:anchor-alias value="TE"/>
334  <x:anchor-alias value="Vary"/>
335  <x:anchor-alias value="WWW-Authenticate"/>
336  The ABNF rules below are defined in other parts:
338<figure><!--Part1--><artwork type="abnf2616">
339  <x:ref>absoluteURI</x:ref>   = &lt;absoluteURI, defined in &general-syntax;&gt;
340  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &general-syntax;&gt;
341  <x:ref>Host</x:ref>          = &lt;Host, defined in &header-host;&gt;
342  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
343  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
344  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &general-syntax;&gt;
345  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
347<figure><!--Part3--><artwork type="abnf2616">
348  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
349  <x:ref>Accept-Charset</x:ref> =
350             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
351  <x:ref>Accept-Encoding</x:ref> =
352             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
353  <x:ref>Accept-Language</x:ref> =
354             &lt;Accept-Language, defined in &header-accept-language;&gt;
356<figure><!--Part4--><artwork type="abnf2616">
357  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
358  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
359  <x:ref>If-Modified-Since</x:ref> =
360             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
361  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
362  <x:ref>If-Unmodified-Since</x:ref> =
363             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
365<figure><!--Part5--><artwork type="abnf2616">
366  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
367  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
368  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
370<figure><!--Part6--><artwork type="abnf2616">
371  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
372  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
374<figure><artwork type="abnf2616">
375  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
376  <x:ref>Proxy-Authenticate</x:ref> =
377             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
378  <x:ref>Proxy-Authorization</x:ref> =
379             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
380  <x:ref>WWW-Authenticate</x:ref> =
381             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
385<section title="Method" anchor="method">
386  <x:anchor-alias value="Method"/>
387  <x:anchor-alias value="extension-method"/>
389   The Method  token indicates the method to be performed on the
390   resource identified by the Request-URI. The method is case-sensitive.
392<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
393  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
394                 | <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
395                 | <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
396                 | <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
397                 | <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
398                 | <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
399                 | <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
400                 | <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
401                 | <x:ref>extension-method</x:ref>
402  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
405   The list of methods allowed by a resource can be specified in an
406   Allow header field (<xref target="header.allow"/>). The return code of the response
407   always notifies the client whether a method is currently allowed on a
408   resource, since the set of allowed methods can change dynamically. An
409   origin server &SHOULD; return the status code 405 (Method Not Allowed)
410   if the method is known by the origin server but not allowed for the
411   requested resource, and 501 (Not Implemented) if the method is
412   unrecognized or not implemented by the origin server. The methods GET
413   and HEAD &MUST; be supported by all general-purpose servers. All other
414   methods are &OPTIONAL;; however, if the above methods are implemented,
415   they &MUST; be implemented with the same semantics as those specified
416   in <xref target="method.definitions"/>.
419<section title="Method Registry" anchor="method.registry">
421  The HTTP Method Registry defines the name space for the Method token in the
422  Request line of an HTTP request.
425  Registrations &MUST; include the following fields:
426  <list style="symbols">
427    <t>Method Name (see <xref target="method"/>)</t>
428    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
429    <t>Pointer to specification text</t>
430  </list>
433  Values to be added to this name space are subject to IETF review
434  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
435  new method names should be traceable through statuses of either 'Obsoletes'
436  or 'Updates' to this document.
439  The registry itself is maintained at <eref target=""/>.
444<section title="Request Header Fields" anchor="request.header.fields">
445  <x:anchor-alias value="extension-code"/>
446  <x:anchor-alias value="request-header"/>
448   The request-header fields allow the client to pass additional
449   information about the request, and about the client itself, to the
450   server. These fields act as request modifiers, with semantics
451   equivalent to the parameters on a programming language method
452   invocation.
454<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
455  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
456                 | <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
457                 | <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
458                 | <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
459                 | <x:ref>Authorization</x:ref>            ; &header-authorization;
460                 | <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
461                 | <x:ref>From</x:ref>                     ; <xref target="header.from"/>
462                 | <x:ref>Host</x:ref>                     ; &header-host;
463                 | <x:ref>If-Match</x:ref>                 ; &header-if-match;
464                 | <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
465                 | <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
466                 | <x:ref>If-Range</x:ref>                 ; &header-if-range;
467                 | <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
468                 | <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
469                 | <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
470                 | <x:ref>Range</x:ref>                    ; &header-range;
471                 | <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
472                 | <x:ref>TE</x:ref>                       ; &header-te;
473                 | <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
476   Request-header field names can be extended reliably only in
477   combination with a change in the protocol version. However, new or
478   experimental header fields &MAY; be given the semantics of request-header
479   fields if all parties in the communication recognize them to
480   be request-header fields. Unrecognized header fields are treated as
481   entity-header fields.
485<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
486  <x:anchor-alias value="Reason-Phrase"/>
487  <x:anchor-alias value="Status-Code"/>
489   The Status-Code element is a 3-digit integer result code of the
490   attempt to understand and satisfy the request. The status codes listed
491   below are defined in <xref target=""/>.
492   The Reason-Phrase is intended to give a short
493   textual description of the Status-Code. The Status-Code is intended
494   for use by automata and the Reason-Phrase is intended for the human
495   user. The client is not required to examine or display the Reason-Phrase.
498   The individual values of the numeric status codes defined for
499   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
500   presented below. The reason phrases listed here are only
501   recommendations -- they &MAY; be replaced by local equivalents without
502   affecting the protocol.
504<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
505  <x:ref>Status-Code</x:ref>    =
506         "100"  ; <xref target="status.100"/>: Continue
507       | "101"  ; <xref target="status.101"/>: Switching Protocols
508       | "200"  ; <xref target="status.200"/>: OK
509       | "201"  ; <xref target="status.201"/>: Created
510       | "202"  ; <xref target="status.202"/>: Accepted
511       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
512       | "204"  ; <xref target="status.204"/>: No Content
513       | "205"  ; <xref target="status.205"/>: Reset Content
514       | "206"  ; <xref target="status.206"/>: Partial Content
515       | "300"  ; <xref target="status.300"/>: Multiple Choices
516       | "301"  ; <xref target="status.301"/>: Moved Permanently
517       | "302"  ; <xref target="status.302"/>: Found
518       | "303"  ; <xref target="status.303"/>: See Other
519       | "304"  ; <xref target="status.304"/>: Not Modified
520       | "305"  ; <xref target="status.305"/>: Use Proxy
521       | "307"  ; <xref target="status.307"/>: Temporary Redirect
522       | "400"  ; <xref target="status.400"/>: Bad Request
523       | "401"  ; <xref target="status.401"/>: Unauthorized
524       | "402"  ; <xref target="status.402"/>: Payment Required
525       | "403"  ; <xref target="status.403"/>: Forbidden
526       | "404"  ; <xref target="status.404"/>: Not Found
527       | "405"  ; <xref target="status.405"/>: Method Not Allowed
528       | "406"  ; <xref target="status.406"/>: Not Acceptable
529       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
530       | "408"  ; <xref target="status.408"/>: Request Time-out
531       | "409"  ; <xref target="status.409"/>: Conflict
532       | "410"  ; <xref target="status.410"/>: Gone
533       | "411"  ; <xref target="status.411"/>: Length Required
534       | "412"  ; <xref target="status.412"/>: Precondition Failed
535       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
536       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
537       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
538       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
539       | "417"  ; <xref target="status.417"/>: Expectation Failed
540       | "500"  ; <xref target="status.500"/>: Internal Server Error
541       | "501"  ; <xref target="status.501"/>: Not Implemented
542       | "502"  ; <xref target="status.502"/>: Bad Gateway
543       | "503"  ; <xref target="status.503"/>: Service Unavailable
544       | "504"  ; <xref target="status.504"/>: Gateway Time-out
545       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
546       | <x:ref>extension-code</x:ref>
548  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
549  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
552   HTTP status codes are extensible. HTTP applications are not required
553   to understand the meaning of all registered status codes, though such
554   understanding is obviously desirable. However, applications &MUST;
555   understand the class of any status code, as indicated by the first
556   digit, and treat any unrecognized response as being equivalent to the
557   x00 status code of that class, with the exception that an
558   unrecognized response &MUST-NOT; be cached. For example, if an
559   unrecognized status code of 431 is received by the client, it can
560   safely assume that there was something wrong with its request and
561   treat the response as if it had received a 400 status code. In such
562   cases, user agents &SHOULD; present to the user the entity returned
563   with the response, since that entity is likely to include human-readable
564   information which will explain the unusual status.
567<section title="Status Code Registry" anchor="status.code.registry">
569  The HTTP Status Code Registry defines the name space for the Status-Code
570  token in the Status line of an HTTP response.
573  Values to be added to this name space are subject to IETF review
574  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
575  new status codes should be traceable through statuses of either 'Obsoletes'
576  or 'Updates' to this document.
579  The registry itself is maintained at <eref target=""/>.
585<section title="Response Header Fields" anchor="response.header.fields">
586  <x:anchor-alias value="response-header"/>
588   The response-header fields allow the server to pass additional
589   information about the response which cannot be placed in the Status-Line.
590   These header fields give information about the server and about
591   further access to the resource identified by the Request-URI.
593<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
594  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
595                  | <x:ref>Age</x:ref>                     ; &header-age;
596                  | <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
597                  | <x:ref>ETag</x:ref>                    ; &header-etag;
598                  | <x:ref>Location</x:ref>                ; <xref target="header.location"/>
599                  | <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
600                  | <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
601                  | <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
602                  | <x:ref>Vary</x:ref>                    ; &header-vary;
603                  | <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
606   Response-header field names can be extended reliably only in
607   combination with a change in the protocol version. However, new or
608   experimental header fields &MAY; be given the semantics of response-header
609   fields if all parties in the communication recognize them to
610   be response-header fields. Unrecognized header fields are treated as
611   entity-header fields.
615<section title="Entity" anchor="entity">
617   Request and Response messages &MAY; transfer an entity if not otherwise
618   restricted by the request method or response status code. An entity
619   consists of entity-header fields and an entity-body, although some
620   responses will only include the entity-headers. HTTP entity-body and
621   entity-header fields are defined in &payload;.
624   An entity-body is only present in a message when a message-body is
625   present, as described in &message-body;. The entity-body is obtained
626   from the message-body by decoding any Transfer-Encoding that might
627   have been applied to ensure safe and proper transfer of the message.
632<section title="Method Definitions" anchor="method.definitions">
634   The set of common methods for HTTP/1.1 is defined below. Although
635   this set can be expanded, additional methods cannot be assumed to
636   share the same semantics for separately extended clients and servers.
639<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
641<section title="Safe Methods" anchor="safe.methods">
642<iref item="Safe Methods" primary="true"/>
644   Implementors should be aware that the software represents the user in
645   their interactions over the Internet, and should be careful to allow
646   the user to be aware of any actions they might take which may have an
647   unexpected significance to themselves or others.
650   In particular, the convention has been established that the GET and
651   HEAD methods &SHOULD-NOT;  have the significance of taking an action
652   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
653   This allows user agents to represent other methods, such as POST, PUT
654   and DELETE, in a special way, so that the user is made aware of the
655   fact that a possibly unsafe action is being requested.
658   Naturally, it is not possible to ensure that the server does not
659   generate side-effects as a result of performing a GET request; in
660   fact, some dynamic resources consider that a feature. The important
661   distinction here is that the user did not request the side-effects,
662   so therefore cannot be held accountable for them.
666<section title="Idempotent Methods" anchor="idempotent.methods">
667<iref item="Idempotent Methods" primary="true"/>
669   Methods can also have the property of "idempotence" in that (aside
670   from error or expiration issues) the side-effects of N &gt; 0 identical
671   requests is the same as for a single request. The methods GET, HEAD,
672   PUT and DELETE share this property. Also, the methods OPTIONS and
673   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
676   However, it is possible that a sequence of several requests is non-idempotent,
677   even if all of the methods executed in that sequence are
678   idempotent. (A sequence is idempotent if a single execution of the
679   entire sequence always yields a result that is not changed by a
680   reexecution of all, or part, of that sequence.) For example, a
681   sequence is non-idempotent if its result depends on a value that is
682   later modified in the same sequence.
685   A sequence that never has side effects is idempotent, by definition
686   (provided that no concurrent operations are being executed on the
687   same set of resources).
692<section title="OPTIONS" anchor="OPTIONS">
693  <rdf:Description>
694    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
695  </rdf:Description>
696  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
697  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
699   The OPTIONS method represents a request for information about the
700   communication options available on the request/response chain
701   identified by the Request-URI. This method allows the client to
702   determine the options and/or requirements associated with a resource,
703   or the capabilities of a server, without implying a resource action
704   or initiating a resource retrieval.
707   Responses to this method are not cacheable.
710   If the OPTIONS request includes an entity-body (as indicated by the
711   presence of Content-Length or Transfer-Encoding), then the media type
712   &MUST; be indicated by a Content-Type field. Although this
713   specification does not define any use for such a body, future
714   extensions to HTTP might use the OPTIONS body to make more detailed
715   queries on the server.
718   If the Request-URI is an asterisk ("*"), the OPTIONS request is
719   intended to apply to the server in general rather than to a specific
720   resource. Since a server's communication options typically depend on
721   the resource, the "*" request is only useful as a "ping" or "no-op"
722   type of method; it does nothing beyond allowing the client to test
723   the capabilities of the server. For example, this can be used to test
724   a proxy for HTTP/1.1 compliance (or lack thereof).
727   If the Request-URI is not an asterisk, the OPTIONS request applies
728   only to the options that are available when communicating with that
729   resource.
732   A 200 response &SHOULD; include any header fields that indicate
733   optional features implemented by the server and applicable to that
734   resource (e.g., Allow), possibly including extensions not defined by
735   this specification. The response body, if any, &SHOULD; also include
736   information about the communication options. The format for such a
737   body is not defined by this specification, but might be defined by
738   future extensions to HTTP. Content negotiation &MAY; be used to select
739   the appropriate response format. If no response body is included, the
740   response &MUST; include a Content-Length field with a field-value of
741   "0".
744   The Max-Forwards request-header field &MAY; be used to target a
745   specific proxy in the request chain. When a proxy receives an OPTIONS
746   request on an absoluteURI for which request forwarding is permitted,
747   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
748   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
749   instead, the proxy &SHOULD; respond with its own communication options.
750   If the Max-Forwards field-value is an integer greater than zero, the
751   proxy &MUST; decrement the field-value when it forwards the request. If
752   no Max-Forwards field is present in the request, then the forwarded
753   request &MUST-NOT; include a Max-Forwards field.
757<section title="GET" anchor="GET">
758  <rdf:Description>
759    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
760  </rdf:Description>
761  <iref primary="true" item="GET method" x:for-anchor=""/>
762  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
764   The GET method means retrieve whatever information (in the form of an
765   entity) is identified by the Request-URI. If the Request-URI refers
766   to a data-producing process, it is the produced data which shall be
767   returned as the entity in the response and not the source text of the
768   process, unless that text happens to be the output of the process.
771   The semantics of the GET method change to a "conditional GET" if the
772   request message includes an If-Modified-Since, If-Unmodified-Since,
773   If-Match, If-None-Match, or If-Range header field. A conditional GET
774   method requests that the entity be transferred only under the
775   circumstances described by the conditional header field(s). The
776   conditional GET method is intended to reduce unnecessary network
777   usage by allowing cached entities to be refreshed without requiring
778   multiple requests or transferring data already held by the client.
781   The semantics of the GET method change to a "partial GET" if the
782   request message includes a Range header field. A partial GET requests
783   that only part of the entity be transferred, as described in &header-range;.
784   The partial GET method is intended to reduce unnecessary
785   network usage by allowing partially-retrieved entities to be
786   completed without transferring data already held by the client.
789   The response to a GET request is cacheable if and only if it meets
790   the requirements for HTTP caching described in &caching;.
793   See <xref target=""/> for security considerations when used for forms.
797<section title="HEAD" anchor="HEAD">
798  <rdf:Description>
799    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
800  </rdf:Description>
801  <iref primary="true" item="HEAD method" x:for-anchor=""/>
802  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
804   The HEAD method is identical to GET except that the server &MUST-NOT;
805   return a message-body in the response. The metainformation contained
806   in the HTTP headers in response to a HEAD request &SHOULD; be identical
807   to the information sent in response to a GET request. This method can
808   be used for obtaining metainformation about the entity implied by the
809   request without transferring the entity-body itself. This method is
810   often used for testing hypertext links for validity, accessibility,
811   and recent modification.
814   The response to a HEAD request &MAY; be cacheable in the sense that the
815   information contained in the response &MAY; be used to update a
816   previously cached entity from that resource. If the new field values
817   indicate that the cached entity differs from the current entity (as
818   would be indicated by a change in Content-Length, Content-MD5, ETag
819   or Last-Modified), then the cache &MUST; treat the cache entry as
820   stale.
824<section title="POST" anchor="POST">
825  <iref primary="true" item="POST method" x:for-anchor=""/>
826  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
828   The POST method is used to request that the origin server accept the
829   entity enclosed in the request as data to be processed by the resource
830   identified by the Request-URI in the Request-Line. POST is designed
831   to allow a uniform method to cover the following functions:
832  <list style="symbols">
833    <t>
834      Annotation of existing resources;
835    </t>
836    <t>
837        Posting a message to a bulletin board, newsgroup, mailing list,
838        or similar group of articles;
839    </t>
840    <t>
841        Providing a block of data, such as the result of submitting a
842        form, to a data-handling process;
843    </t>
844    <t>
845        Extending a database through an append operation.
846    </t>
847  </list>
850   The actual function performed by the POST method is determined by the
851   server and is usually dependent on the Request-URI.
854   The action performed by the POST method might not result in a
855   resource that can be identified by a URI. In this case, either 200
856   (OK) or 204 (No Content) is the appropriate response status,
857   depending on whether or not the response includes an entity that
858   describes the result.
861   If a resource has been created on the origin server, the response
862   &SHOULD; be 201 (Created) and contain an entity which describes the
863   status of the request and refers to the new resource, and a Location
864   header (see <xref target="header.location"/>).
867   Responses to this method are not cacheable, unless the response
868   includes appropriate Cache-Control or Expires header fields. However,
869   the 303 (See Other) response can be used to direct the user agent to
870   retrieve a cacheable resource.
874<section title="PUT" anchor="PUT">
875  <iref primary="true" item="PUT method" x:for-anchor=""/>
876  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
878   The PUT method requests that the enclosed entity be stored at the
879   supplied Request-URI. If the Request-URI refers to an already
880   existing resource, the enclosed entity &SHOULD; be considered as a
881   modified version of the one residing on the origin server. If the
882   Request-URI does not point to an existing resource, and that URI is
883   capable of being defined as a new resource by the requesting user
884   agent, the origin server can create the resource with that URI. If a
885   new resource is created at the Request-URI, the origin server &MUST;
886         inform the user agent
887   via the 201 (Created) response. If an existing resource is modified,
888   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
889   to indicate successful completion of the request. If the resource
890   could not be created or modified with the Request-URI, an appropriate
891   error response &SHOULD; be given that reflects the nature of the
892   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
893   headers (headers starting with the prefix 'Content-') that it does
894   not understand or implement
895   and &MUST; return a 501 (Not Implemented) response in such cases.
898   If the request passes through a cache and the Request-URI identifies
899   one or more currently cached entities, those entries &SHOULD; be
900   treated as stale. Responses to this method are not cacheable.
903   The fundamental difference between the POST and PUT requests is
904   reflected in the different meaning of the Request-URI. The URI in a
905   POST request identifies the resource that will handle the enclosed
906   entity. That resource might be a data-accepting process, a gateway to
907   some other protocol, or a separate entity that accepts annotations.
908   In contrast, the URI in a PUT request identifies the entity enclosed
909   with the request -- the user agent knows what URI is intended and the
910   server &MUST-NOT; attempt to apply the request to some other resource.
911   If the server desires that the request be applied to a different URI,
912   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
913   then make its own decision regarding whether or not to redirect the
914   request.
917   A single resource &MAY; be identified by many different URIs. For
918   example, an article might have a URI for identifying "the current
919   version" which is separate from the URI identifying each particular
920   version. In this case, a PUT request on a general URI might result in
921   several other URIs being defined by the origin server.
924   HTTP/1.1 does not define how a PUT method affects the state of an
925   origin server.
928   Unless otherwise specified for a particular entity-header, the
929   entity-headers in the PUT request &SHOULD; be applied to the resource
930   created or modified by the PUT.
934<section title="DELETE" anchor="DELETE">
935  <iref primary="true" item="DELETE method" x:for-anchor=""/>
936  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
938   The DELETE method requests that the origin server delete the resource
939   identified by the Request-URI. This method &MAY; be overridden by human
940   intervention (or other means) on the origin server. The client cannot
941   be guaranteed that the operation has been carried out, even if the
942   status code returned from the origin server indicates that the action
943   has been completed successfully. However, the server &SHOULD-NOT;
944   indicate success unless, at the time the response is given, it
945   intends to delete the resource or move it to an inaccessible
946   location.
949   A successful response &SHOULD; be 200 (OK) if the response includes an
950   entity describing the status, 202 (Accepted) if the action has not
951   yet been enacted, or 204 (No Content) if the action has been enacted
952   but the response does not include an entity.
955   If the request passes through a cache and the Request-URI identifies
956   one or more currently cached entities, those entries &SHOULD; be
957   treated as stale. Responses to this method are not cacheable.
961<section title="TRACE" anchor="TRACE">
962  <rdf:Description>
963    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
964  </rdf:Description>
965  <iref primary="true" item="TRACE method" x:for-anchor=""/>
966  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
968   The TRACE method is used to invoke a remote, application-layer loop-back
969   of the request message. The final recipient of the request
970   &SHOULD; reflect the message received back to the client as the
971   entity-body of a 200 (OK) response. The final recipient is either the
972   origin server or the first proxy or gateway to receive a Max-Forwards
973   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
974   &MUST-NOT; include an entity.
977   TRACE allows the client to see what is being received at the other
978   end of the request chain and use that data for testing or diagnostic
979   information. The value of the Via header field (&header-via;) is of
980   particular interest, since it acts as a trace of the request chain.
981   Use of the Max-Forwards header field allows the client to limit the
982   length of the request chain, which is useful for testing a chain of
983   proxies forwarding messages in an infinite loop.
986   If the request is valid, the response &SHOULD; contain the entire
987   request message in the entity-body, with a Content-Type of
988   "message/http" (see &media-type-message-http;). Responses to this method
989   &MUST-NOT; be cached.
993<section title="CONNECT" anchor="CONNECT">
994  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
995  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
997   This specification reserves the method name CONNECT for use with a
998   proxy that can dynamically switch to being a tunnel (e.g. SSL
999   tunneling <xref target="RFC2817"/>).
1005<section title="Status Code Definitions" anchor="">
1007   Each Status-Code is described below, including a description of which
1008   method(s) it can follow and any metainformation required in the
1009   response.
1012<section title="Informational 1xx" anchor="status.1xx">
1014   This class of status code indicates a provisional response,
1015   consisting only of the Status-Line and optional headers, and is
1016   terminated by an empty line. There are no required headers for this
1017   class of status code. Since HTTP/1.0 did not define any 1xx status
1018   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1019   except under experimental conditions.
1022   A client &MUST; be prepared to accept one or more 1xx status responses
1023   prior to a regular response, even if the client does not expect a 100
1024   (Continue) status message. Unexpected 1xx status responses &MAY; be
1025   ignored by a user agent.
1028   Proxies &MUST; forward 1xx responses, unless the connection between the
1029   proxy and its client has been closed, or unless the proxy itself
1030   requested the generation of the 1xx response. (For example, if a
1031   proxy adds a "Expect: 100-continue" field when it forwards a request,
1032   then it need not forward the corresponding 100 (Continue)
1033   response(s).)
1036<section title="100 Continue" anchor="status.100">
1037  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1038  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1040   The client &SHOULD; continue with its request. This interim response is
1041   used to inform the client that the initial part of the request has
1042   been received and has not yet been rejected by the server. The client
1043   &SHOULD; continue by sending the remainder of the request or, if the
1044   request has already been completed, ignore this response. The server
1045   &MUST; send a final response after the request has been completed. See
1046   &use100; for detailed discussion of the use and handling of this
1047   status code.
1051<section title="101 Switching Protocols" anchor="status.101">
1052  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1053  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1055   The server understands and is willing to comply with the client's
1056   request, via the Upgrade message header field (&header-upgrade;), for a
1057   change in the application protocol being used on this connection. The
1058   server will switch protocols to those defined by the response's
1059   Upgrade header field immediately after the empty line which
1060   terminates the 101 response.
1063   The protocol &SHOULD; be switched only when it is advantageous to do
1064   so. For example, switching to a newer version of HTTP is advantageous
1065   over older versions, and switching to a real-time, synchronous
1066   protocol might be advantageous when delivering resources that use
1067   such features.
1072<section title="Successful 2xx" anchor="status.2xx">
1074   This class of status code indicates that the client's request was
1075   successfully received, understood, and accepted.
1078<section title="200 OK" anchor="status.200">
1079  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1080  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1082   The request has succeeded. The information returned with the response
1083   is dependent on the method used in the request, for example:
1084  <list style="hanging">
1085    <t hangText="GET">
1086          an entity corresponding to the requested resource is sent in
1087          the response;
1088    </t>
1089    <t hangText="HEAD">
1090          the entity-header fields corresponding to the requested
1091          resource are sent in the response without any message-body;
1092    </t>
1093    <t hangText="POST">
1094      an entity describing or containing the result of the action;
1095    </t>
1096    <t hangText="TRACE">
1097      an entity containing the request message as received by the
1098      end server.
1099    </t>
1100  </list>
1104<section title="201 Created" anchor="status.201">
1105  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1106  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1108   The request has been fulfilled and resulted in a new resource being
1109   created. The newly created resource can be referenced by the URI(s)
1110   returned in the entity of the response, with the most specific URI
1111   for the resource given by a Location header field. The response
1112   &SHOULD; include an entity containing a list of resource
1113   characteristics and location(s) from which the user or user agent can
1114   choose the one most appropriate. The entity format is specified by
1115   the media type given in the Content-Type header field. The origin
1116   server &MUST; create the resource before returning the 201 status code.
1117   If the action cannot be carried out immediately, the server &SHOULD;
1118   respond with 202 (Accepted) response instead.
1121   A 201 response &MAY; contain an ETag response header field indicating
1122   the current value of the entity tag for the requested variant just
1123   created, see &header-etag;.
1127<section title="202 Accepted" anchor="status.202">
1128  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1129  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1131   The request has been accepted for processing, but the processing has
1132   not been completed.  The request might or might not eventually be
1133   acted upon, as it might be disallowed when processing actually takes
1134   place. There is no facility for re-sending a status code from an
1135   asynchronous operation such as this.
1138   The 202 response is intentionally non-committal. Its purpose is to
1139   allow a server to accept a request for some other process (perhaps a
1140   batch-oriented process that is only run once per day) without
1141   requiring that the user agent's connection to the server persist
1142   until the process is completed. The entity returned with this
1143   response &SHOULD; include an indication of the request's current status
1144   and either a pointer to a status monitor or some estimate of when the
1145   user can expect the request to be fulfilled.
1149<section title="203 Non-Authoritative Information" anchor="status.203">
1150  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1151  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1153   The returned metainformation in the entity-header is not the
1154   definitive set as available from the origin server, but is gathered
1155   from a local or a third-party copy. The set presented &MAY; be a subset
1156   or superset of the original version. For example, including local
1157   annotation information about the resource might result in a superset
1158   of the metainformation known by the origin server. Use of this
1159   response code is not required and is only appropriate when the
1160   response would otherwise be 200 (OK).
1164<section title="204 No Content" anchor="status.204">
1165  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1166  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1168   The server has fulfilled the request but does not need to return an
1169   entity-body, and might want to return updated metainformation. The
1170   response &MAY; include new or updated metainformation in the form of
1171   entity-headers, which if present &SHOULD; be associated with the
1172   requested variant.
1175   If the client is a user agent, it &SHOULD-NOT;  change its document view
1176   from that which caused the request to be sent. This response is
1177   primarily intended to allow input for actions to take place without
1178   causing a change to the user agent's active document view, although
1179   any new or updated metainformation &SHOULD; be applied to the document
1180   currently in the user agent's active view.
1183   The 204 response &MUST-NOT; include a message-body, and thus is always
1184   terminated by the first empty line after the header fields.
1188<section title="205 Reset Content" anchor="status.205">
1189  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1190  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1192   The server has fulfilled the request and the user agent &SHOULD; reset
1193   the document view which caused the request to be sent. This response
1194   is primarily intended to allow input for actions to take place via
1195   user input, followed by a clearing of the form in which the input is
1196   given so that the user can easily initiate another input action. The
1197   response &MUST-NOT; include an entity.
1201<section title="206 Partial Content" anchor="status.206">
1202  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1203  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1205   The server has fulfilled the partial GET request for the resource
1206   and the enclosed entity is a partial representation as defined in &range;.
1211<section title="Redirection 3xx" anchor="status.3xx">
1213   This class of status code indicates that further action needs to be
1214   taken by the user agent in order to fulfill the request.  The action
1215   required &MAY; be carried out by the user agent without interaction
1216   with the user if and only if the method used in the second request is
1217   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1218   such loops generate network traffic for each redirection.
1219  <list><t>
1220      <x:h>Note:</x:h> previous versions of this specification recommended a
1221      maximum of five redirections. Content developers should be aware
1222      that there might be clients that implement such a fixed
1223      limitation.
1224  </t></list>
1227<section title="300 Multiple Choices" anchor="status.300">
1228  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1229  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1231   The requested resource corresponds to any one of a set of
1232   representations, each with its own specific location, and agent-driven
1233   negotiation information (&content-negotiation;) is being provided so that
1234   the user (or user agent) can select a preferred representation and
1235   redirect its request to that location.
1238   Unless it was a HEAD request, the response &SHOULD; include an entity
1239   containing a list of resource characteristics and location(s) from
1240   which the user or user agent can choose the one most appropriate. The
1241   entity format is specified by the media type given in the Content-Type
1242   header field. Depending upon the format and the capabilities of
1243   the user agent, selection of the most appropriate choice &MAY; be
1244   performed automatically. However, this specification does not define
1245   any standard for such automatic selection.
1248   If the server has a preferred choice of representation, it &SHOULD;
1249   include the specific URI for that representation in the Location
1250   field; user agents &MAY; use the Location field value for automatic
1251   redirection. This response is cacheable unless indicated otherwise.
1255<section title="301 Moved Permanently" anchor="status.301">
1256  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1257  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1259   The requested resource has been assigned a new permanent URI and any
1260   future references to this resource &SHOULD; use one of the returned
1261   URIs.  Clients with link editing capabilities ought to automatically
1262   re-link references to the Request-URI to one or more of the new
1263   references returned by the server, where possible. This response is
1264   cacheable unless indicated otherwise.
1267   The new permanent URI &SHOULD; be given by the Location field in the
1268   response. Unless the request method was HEAD, the entity of the
1269   response &SHOULD; contain a short hypertext note with a hyperlink to
1270   the new URI(s).
1273   If the 301 status code is received in response to a request method
1274   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1275   then the request &MAY; be automatically redirected by the user agent without
1276   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1277   request unless it can be confirmed by the user, since this might
1278   change the conditions under which the request was issued.
1279  <list><t>
1280      <x:h>Note:</x:h> When automatically redirecting a POST request after
1281      receiving a 301 status code, some existing HTTP/1.0 user agents
1282      will erroneously change it into a GET request.
1283  </t></list>
1287<section title="302 Found" anchor="status.302">
1288  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1289  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1291   The requested resource resides temporarily under a different URI.
1292   Since the redirection might be altered on occasion, the client &SHOULD;
1293   continue to use the Request-URI for future requests.  This response
1294   is only cacheable if indicated by a Cache-Control or Expires header
1295   field.
1298   The temporary URI &SHOULD; be given by the Location field in the
1299   response. Unless the request method was HEAD, the entity of the
1300   response &SHOULD; contain a short hypertext note with a hyperlink to
1301   the new URI(s).
1304   If the 302 status code is received in response to a request method
1305   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1306   then the request &MAY; be automatically redirected by the user agent without
1307   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1308   request unless it can be confirmed by the user, since this might
1309   change the conditions under which the request was issued.
1310  <list><t>
1311      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1312      to change the method on the redirected request.  However, most
1313      existing user agent implementations treat 302 as if it were a 303
1314      response, performing a GET on the Location field-value regardless
1315      of the original request method. The status codes 303 and 307 have
1316      been added for servers that wish to make unambiguously clear which
1317      kind of reaction is expected of the client.
1318  </t></list>
1322<section title="303 See Other" anchor="status.303">
1323  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1324  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1326   The server directs the user agent to a different resource, indicated
1327   by a URI in the Location header field, that provides an indirect
1328   response to the original request.  The user agent &MAY; perform a GET
1329   request on the URI in the Location field in order to obtain a
1330   representation corresponding to the response, be redirected again,
1331   or end with an error status.  The Location URI is not a substitute
1332   reference for the originally requested resource.
1335   The 303 status is generally applicable to any HTTP method.  It is
1336   primarily used to allow the output of a POST action to redirect
1337   the user agent to a selected resource, since doing so provides the
1338   information corresponding to the POST response in a form that
1339   can be separately identified, bookmarked, and cached independent
1340   of the original request.
1343   A 303 response to a GET request indicates that the requested
1344   resource does not have a representation of its own that can be
1345   transferred by the server over HTTP.  The Location URI indicates a
1346   resource that is descriptive of the requested resource such that
1347   the follow-on representation may be useful without implying that
1348   it adequately represents the previously requested resource.
1349   Note that answers to the questions of what can be represented, what
1350   representations are adequate, and what might be a useful description
1351   are outside the scope of HTTP and thus entirely determined by the
1352   resource owner(s).
1355   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1356   cacheable by Cache-Control or Expires header fields.  Except for
1357   responses to a HEAD request, the entity of a 303 response &SHOULD;
1358   contain a short hypertext note with a hyperlink to the Location URI.
1362<section title="304 Not Modified" anchor="status.304">
1363  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1364  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1366   The response to the request has not been modified since the conditions
1367   indicated by the client's conditional GET request, as defined in &conditional;.
1371<section title="305 Use Proxy" anchor="status.305">
1372  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1373  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1375   The 305 status was defined in a previous version of this specification
1376   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1380<section title="306 (Unused)" anchor="status.306">
1381  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1382  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1384   The 306 status code was used in a previous version of the
1385   specification, is no longer used, and the code is reserved.
1389<section title="307 Temporary Redirect" anchor="status.307">
1390  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1391  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1393   The requested resource resides temporarily under a different URI.
1394   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1395   continue to use the Request-URI for future requests.  This response
1396   is only cacheable if indicated by a Cache-Control or Expires header
1397   field.
1400   The temporary URI &SHOULD; be given by the Location field in the
1401   response. Unless the request method was HEAD, the entity of the
1402   response &SHOULD; contain a short hypertext note with a hyperlink to
1403   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1404   understand the 307 status. Therefore, the note &SHOULD; contain the
1405   information necessary for a user to repeat the original request on
1406   the new URI.
1409   If the 307 status code is received in response to a request method
1410   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1411   then the request &MAY; be automatically redirected by the user agent without
1412   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1413   request unless it can be confirmed by the user, since this might
1414   change the conditions under which the request was issued.
1419<section title="Client Error 4xx" anchor="status.4xx">
1421   The 4xx class of status code is intended for cases in which the
1422   client seems to have erred. Except when responding to a HEAD request,
1423   the server &SHOULD; include an entity containing an explanation of the
1424   error situation, and whether it is a temporary or permanent
1425   condition. These status codes are applicable to any request method.
1426   User agents &SHOULD; display any included entity to the user.
1429   If the client is sending data, a server implementation using TCP
1430   &SHOULD; be careful to ensure that the client acknowledges receipt of
1431   the packet(s) containing the response, before the server closes the
1432   input connection. If the client continues sending data to the server
1433   after the close, the server's TCP stack will send a reset packet to
1434   the client, which may erase the client's unacknowledged input buffers
1435   before they can be read and interpreted by the HTTP application.
1438<section title="400 Bad Request" anchor="status.400">
1439  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1440  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1442   The request could not be understood by the server due to malformed
1443   syntax. The client &SHOULD-NOT;  repeat the request without
1444   modifications.
1448<section title="401 Unauthorized" anchor="status.401">
1449  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1450  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1452   The request requires user authentication (see &auth;).
1456<section title="402 Payment Required" anchor="status.402">
1457  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1458  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1460   This code is reserved for future use.
1464<section title="403 Forbidden" anchor="status.403">
1465  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1466  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1468   The server understood the request, but is refusing to fulfill it.
1469   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1470   If the request method was not HEAD and the server wishes to make
1471   public why the request has not been fulfilled, it &SHOULD; describe the
1472   reason for the refusal in the entity.  If the server does not wish to
1473   make this information available to the client, the status code 404
1474   (Not Found) can be used instead.
1478<section title="404 Not Found" anchor="status.404">
1479  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1480  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1482   The server has not found anything matching the Request-URI. No
1483   indication is given of whether the condition is temporary or
1484   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1485   knows, through some internally configurable mechanism, that an old
1486   resource is permanently unavailable and has no forwarding address.
1487   This status code is commonly used when the server does not wish to
1488   reveal exactly why the request has been refused, or when no other
1489   response is applicable.
1493<section title="405 Method Not Allowed" anchor="status.405">
1494  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1495  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1497   The method specified in the Request-Line is not allowed for the
1498   resource identified by the Request-URI. The response &MUST; include an
1499   Allow header containing a list of valid methods for the requested
1500   resource.
1504<section title="406 Not Acceptable" anchor="status.406">
1505  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1506  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1508   The resource identified by the request is only capable of generating
1509   response entities which have content characteristics not acceptable
1510   according to the accept headers sent in the request.
1513   Unless it was a HEAD request, the response &SHOULD; include an entity
1514   containing a list of available entity characteristics and location(s)
1515   from which the user or user agent can choose the one most
1516   appropriate. The entity format is specified by the media type given
1517   in the Content-Type header field. Depending upon the format and the
1518   capabilities of the user agent, selection of the most appropriate
1519   choice &MAY; be performed automatically. However, this specification
1520   does not define any standard for such automatic selection.
1521  <list><t>
1522      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1523      not acceptable according to the accept headers sent in the
1524      request. In some cases, this may even be preferable to sending a
1525      406 response. User agents are encouraged to inspect the headers of
1526      an incoming response to determine if it is acceptable.
1527  </t></list>
1530   If the response could be unacceptable, a user agent &SHOULD;
1531   temporarily stop receipt of more data and query the user for a
1532   decision on further actions.
1536<section title="407 Proxy Authentication Required" anchor="status.407">
1537  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1538  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1540   This code is similar to 401 (Unauthorized), but indicates that the
1541   client must first authenticate itself with the proxy (see &auth;).
1545<section title="408 Request Timeout" anchor="status.408">
1546  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1547  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1549   The client did not produce a request within the time that the server
1550   was prepared to wait. The client &MAY; repeat the request without
1551   modifications at any later time.
1555<section title="409 Conflict" anchor="status.409">
1556  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1559   The request could not be completed due to a conflict with the current
1560   state of the resource. This code is only allowed in situations where
1561   it is expected that the user might be able to resolve the conflict
1562   and resubmit the request. The response body &SHOULD; include enough
1563   information for the user to recognize the source of the conflict.
1564   Ideally, the response entity would include enough information for the
1565   user or user agent to fix the problem; however, that might not be
1566   possible and is not required.
1569   Conflicts are most likely to occur in response to a PUT request. For
1570   example, if versioning were being used and the entity being PUT
1571   included changes to a resource which conflict with those made by an
1572   earlier (third-party) request, the server might use the 409 response
1573   to indicate that it can't complete the request. In this case, the
1574   response entity would likely contain a list of the differences
1575   between the two versions in a format defined by the response
1576   Content-Type.
1580<section title="410 Gone" anchor="status.410">
1581  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1582  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1584   The requested resource is no longer available at the server and no
1585   forwarding address is known. This condition is expected to be
1586   considered permanent. Clients with link editing capabilities &SHOULD;
1587   delete references to the Request-URI after user approval. If the
1588   server does not know, or has no facility to determine, whether or not
1589   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1590   used instead. This response is cacheable unless indicated otherwise.
1593   The 410 response is primarily intended to assist the task of web
1594   maintenance by notifying the recipient that the resource is
1595   intentionally unavailable and that the server owners desire that
1596   remote links to that resource be removed. Such an event is common for
1597   limited-time, promotional services and for resources belonging to
1598   individuals no longer working at the server's site. It is not
1599   necessary to mark all permanently unavailable resources as "gone" or
1600   to keep the mark for any length of time -- that is left to the
1601   discretion of the server owner.
1605<section title="411 Length Required" anchor="status.411">
1606  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1607  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1609   The server refuses to accept the request without a defined Content-Length.
1610   The client &MAY; repeat the request if it adds a valid
1611   Content-Length header field containing the length of the message-body
1612   in the request message.
1616<section title="412 Precondition Failed" anchor="status.412">
1617  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1618  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1620   The precondition given in one or more of the request-header fields
1621   evaluated to false when it was tested on the server, as defined in
1622   &conditional;.
1626<section title="413 Request Entity Too Large" anchor="status.413">
1627  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1628  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1630   The server is refusing to process a request because the request
1631   entity is larger than the server is willing or able to process. The
1632   server &MAY; close the connection to prevent the client from continuing
1633   the request.
1636   If the condition is temporary, the server &SHOULD; include a Retry-After
1637   header field to indicate that it is temporary and after what
1638   time the client &MAY; try again.
1642<section title="414 Request-URI Too Long" anchor="status.414">
1643  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1644  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1646   The server is refusing to service the request because the Request-URI
1647   is longer than the server is willing to interpret. This rare
1648   condition is only likely to occur when a client has improperly
1649   converted a POST request to a GET request with long query
1650   information, when the client has descended into a URI "black hole" of
1651   redirection (e.g., a redirected URI prefix that points to a suffix of
1652   itself), or when the server is under attack by a client attempting to
1653   exploit security holes present in some servers using fixed-length
1654   buffers for reading or manipulating the Request-URI.
1658<section title="415 Unsupported Media Type" anchor="status.415">
1659  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1660  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1662   The server is refusing to service the request because the entity of
1663   the request is in a format not supported by the requested resource
1664   for the requested method.
1668<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1669  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1670  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1672   The request included a Range request-header field (&header-range;) and none of
1673   the range-specifier values in this field overlap the current extent
1674   of the selected resource.
1678<section title="417 Expectation Failed" anchor="status.417">
1679  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1680  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1682   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1683   could not be met by this server, or, if the server is a proxy,
1684   the server has unambiguous evidence that the request could not be met
1685   by the next-hop server.
1690<section title="Server Error 5xx" anchor="status.5xx">
1692   Response status codes beginning with the digit "5" indicate cases in
1693   which the server is aware that it has erred or is incapable of
1694   performing the request. Except when responding to a HEAD request, the
1695   server &SHOULD; include an entity containing an explanation of the
1696   error situation, and whether it is a temporary or permanent
1697   condition. User agents &SHOULD; display any included entity to the
1698   user. These response codes are applicable to any request method.
1701<section title="500 Internal Server Error" anchor="status.500">
1702  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1703  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1705   The server encountered an unexpected condition which prevented it
1706   from fulfilling the request.
1710<section title="501 Not Implemented" anchor="status.501">
1711  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1712  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1714   The server does not support the functionality required to fulfill the
1715   request. This is the appropriate response when the server does not
1716   recognize the request method and is not capable of supporting it for
1717   any resource.
1721<section title="502 Bad Gateway" anchor="status.502">
1722  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1723  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1725   The server, while acting as a gateway or proxy, received an invalid
1726   response from the upstream server it accessed in attempting to
1727   fulfill the request.
1731<section title="503 Service Unavailable" anchor="status.503">
1732  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1733  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1735   The server is currently unable to handle the request due to a
1736   temporary overloading or maintenance of the server. The implication
1737   is that this is a temporary condition which will be alleviated after
1738   some delay. If known, the length of the delay &MAY; be indicated in a
1739   Retry-After header. If no Retry-After is given, the client &SHOULD;
1740   handle the response as it would for a 500 response.
1741  <list><t>
1742      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1743      server must use it when becoming overloaded. Some servers may wish
1744      to simply refuse the connection.
1745  </t></list>
1749<section title="504 Gateway Timeout" anchor="status.504">
1750  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1751  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1753   The server, while acting as a gateway or proxy, did not receive a
1754   timely response from the upstream server specified by the URI (e.g.
1755   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1756   to access in attempting to complete the request.
1757  <list><t>
1758      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1759      return 400 or 500 when DNS lookups time out.
1760  </t></list>
1764<section title="505 HTTP Version Not Supported" anchor="status.505">
1765  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1766  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1768   The server does not support, or refuses to support, the protocol
1769   version that was used in the request message. The server is
1770   indicating that it is unable or unwilling to complete the request
1771   using the same major version as the client, as described in &http-version;,
1772   other than with this error message. The response &SHOULD; contain
1773   an entity describing why that version is not supported and what other
1774   protocols are supported by that server.
1782<section title="Header Field Definitions" anchor="header.fields">
1784   This section defines the syntax and semantics of HTTP/1.1 header fields
1785   related to request and response semantics.
1788   For entity-header fields, both sender and recipient refer to either the
1789   client or the server, depending on who sends and who receives the entity.
1792<section title="Allow" anchor="header.allow">
1793  <iref primary="true" item="Allow header" x:for-anchor=""/>
1794  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1795  <x:anchor-alias value="Allow"/>
1797      The Allow response-header field lists the set of methods advertised as
1798      supported by the resource identified by the Request-URI. The purpose of
1799      this field is strictly to inform the recipient of valid methods
1800      associated with the resource. An Allow header field &MUST; be
1801      present in a 405 (Method Not Allowed) response.
1803<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1804  <x:ref>Allow</x:ref>   = "Allow" ":" #<x:ref>Method</x:ref>
1807      Example of use:
1809<figure><artwork type="example">
1810       Allow: GET, HEAD, PUT
1813      The actual set of allowed methods is defined
1814      by the origin server at the time of each request.
1817      A proxy &MUST-NOT; modify the Allow header field even if it does not
1818      understand all the methods specified, since the user agent might
1819      have other means of communicating with the origin server.
1823<section title="Expect" anchor="header.expect">
1824  <iref primary="true" item="Expect header" x:for-anchor=""/>
1825  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1826  <x:anchor-alias value="Expect"/>
1827  <x:anchor-alias value="expectation"/>
1828  <x:anchor-alias value="expectation-extension"/>
1829  <x:anchor-alias value="expect-params"/>
1831   The Expect request-header field is used to indicate that particular
1832   server behaviors are required by the client.
1834<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1835  <x:ref>Expect</x:ref>       =  "Expect" ":" 1#<x:ref>expectation</x:ref>
1837  <x:ref>expectation</x:ref>  =  "100-continue" | <x:ref>expectation-extension</x:ref>
1838  <x:ref>expectation-extension</x:ref> =  <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> | <x:ref>quoted-string</x:ref> )
1839                           *<x:ref>expect-params</x:ref> ]
1840  <x:ref>expect-params</x:ref> =  ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> | <x:ref>quoted-string</x:ref> ) ]
1843   A server that does not understand or is unable to comply with any of
1844   the expectation values in the Expect field of a request &MUST; respond
1845   with appropriate error status. The server &MUST; respond with a 417
1846   (Expectation Failed) status if any of the expectations cannot be met
1847   or, if there are other problems with the request, some other 4xx
1848   status.
1851   This header field is defined with extensible syntax to allow for
1852   future extensions. If a server receives a request containing an
1853   Expect field that includes an expectation-extension that it does not
1854   support, it &MUST; respond with a 417 (Expectation Failed) status.
1857   Comparison of expectation values is case-insensitive for unquoted
1858   tokens (including the 100-continue token), and is case-sensitive for
1859   quoted-string expectation-extensions.
1862   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1863   return a 417 (Expectation Failed) status if it receives a request
1864   with an expectation that it cannot meet. However, the Expect
1865   request-header itself is end-to-end; it &MUST; be forwarded if the
1866   request is forwarded.
1869   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1870   Expect header.
1873   See &use100; for the use of the 100 (Continue) status.
1877<section title="From" anchor="header.from">
1878  <iref primary="true" item="From header" x:for-anchor=""/>
1879  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1880  <x:anchor-alias value="From"/>
1881  <x:anchor-alias value="mailbox"/>
1883   The From request-header field, if given, &SHOULD; contain an Internet
1884   e-mail address for the human user who controls the requesting user
1885   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1886   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1888<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1889  <x:ref>From</x:ref>    = "From" ":" <x:ref>mailbox</x:ref>
1891  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1894   An example is:
1896<figure><artwork type="example">
1897    From:
1900   This header field &MAY; be used for logging purposes and as a means for
1901   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1902   be used as an insecure form of access protection. The interpretation
1903   of this field is that the request is being performed on behalf of the
1904   person given, who accepts responsibility for the method performed. In
1905   particular, robot agents &SHOULD; include this header so that the
1906   person responsible for running the robot can be contacted if problems
1907   occur on the receiving end.
1910   The Internet e-mail address in this field &MAY; be separate from the
1911   Internet host which issued the request. For example, when a request
1912   is passed through a proxy the original issuer's address &SHOULD; be
1913   used.
1916   The client &SHOULD-NOT;  send the From header field without the user's
1917   approval, as it might conflict with the user's privacy interests or
1918   their site's security policy. It is strongly recommended that the
1919   user be able to disable, enable, and modify the value of this field
1920   at any time prior to a request.
1924<section title="Location" anchor="header.location">
1925  <iref primary="true" item="Location header" x:for-anchor=""/>
1926  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1927  <x:anchor-alias value="Location"/>
1929   The Location response-header field is used for the identification of a
1930   new resource or to redirect the recipient to a location other than the
1931   Request-URI for completion of the request.  For 201 (Created)
1932   responses, the Location is that of the new resource which was created
1933   by the request. For 3xx responses, the location &SHOULD; indicate the
1934   server's preferred URI for automatic redirection to the resource. The
1935   field value consists of a single absolute URI.
1937<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1938  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>absoluteURI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1941   An example is:
1943<figure><artwork type="example">
1944    Location:
1947  <list><t>
1948      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1949      from Location in that the Content-Location identifies the original
1950      location of the entity enclosed in the response. It is therefore
1951      possible for a response to contain header fields for both Location
1952      and Content-Location.
1953  </t></list>
1956   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1957   <list style="symbols">
1958      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1959      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1960      <t>With 305 Use Proxy.</t>
1961   </list>
1965<section title="Max-Forwards" anchor="header.max-forwards">
1966  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1967  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1968  <x:anchor-alias value="Max-Forwards"/>
1970   The Max-Forwards request-header field provides a mechanism with the
1971   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1972   number of proxies or gateways that can forward the request to the
1973   next inbound server. This can be useful when the client is attempting
1974   to trace a request chain which appears to be failing or looping in
1975   mid-chain.
1977<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1978  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" 1*<x:ref>DIGIT</x:ref>
1981   The Max-Forwards value is a decimal integer indicating the remaining
1982   number of times this request message may be forwarded.
1985   Each proxy or gateway recipient of a TRACE or OPTIONS request
1986   containing a Max-Forwards header field &MUST; check and update its
1987   value prior to forwarding the request. If the received value is zero
1988   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1989   respond as the final recipient. If the received Max-Forwards value is
1990   greater than zero, then the forwarded message &MUST; contain an updated
1991   Max-Forwards field with a value decremented by one (1).
1994   The Max-Forwards header field &MAY; be ignored for all other methods
1995   defined by this specification and for any extension methods for which
1996   it is not explicitly referred to as part of that method definition.
2000<section title="Referer" anchor="header.referer">
2001  <iref primary="true" item="Referer header" x:for-anchor=""/>
2002  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2003  <x:anchor-alias value="Referer"/>
2005   The Referer[sic] request-header field allows the client to specify,
2006   for the server's benefit, the address (URI) of the resource from
2007   which the Request-URI was obtained (the "referrer", although the
2008   header field is misspelled.) The Referer request-header allows a
2009   server to generate lists of back-links to resources for interest,
2010   logging, optimized caching, etc. It also allows obsolete or mistyped
2011   links to be traced for maintenance. The Referer field &MUST-NOT; be
2012   sent if the Request-URI was obtained from a source that does not have
2013   its own URI, such as input from the user keyboard.
2015<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2016  <x:ref>Referer</x:ref>        = "Referer" ":" ( <x:ref>absoluteURI</x:ref> | <x:ref>relativeURI</x:ref> )
2019   Example:
2021<figure><artwork type="example">
2022    Referer:
2025   If the field value is a relative URI, it &SHOULD; be interpreted
2026   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2027   <xref target=""/> for security considerations.
2031<section title="Retry-After" anchor="header.retry-after">
2032  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2033  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2034  <x:anchor-alias value="Retry-After"/>
2036   The Retry-After response-header field can be used with a 503 (Service
2037   Unavailable) response to indicate how long the service is expected to
2038   be unavailable to the requesting client. This field &MAY; also be used
2039   with any 3xx (Redirection) response to indicate the minimum time the
2040   user-agent is asked wait before issuing the redirected request. The
2041   value of this field can be either an HTTP-date or an integer number
2042   of seconds (in decimal) after the time of the response.
2044<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2045  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" ( <x:ref>HTTP-date</x:ref> | <x:ref>delta-seconds</x:ref> )
2047<t anchor="">
2048  <x:anchor-alias value="delta-seconds"/>
2049   Time spans are non-negative decimal integers, representing time in
2050   seconds.
2052<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2053  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2056   Two examples of its use are
2058<figure><artwork type="example">
2059    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2060    Retry-After: 120
2063   In the latter example, the delay is 2 minutes.
2067<section title="Server" anchor="header.server">
2068  <iref primary="true" item="Server header" x:for-anchor=""/>
2069  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2070  <x:anchor-alias value="Server"/>
2072   The Server response-header field contains information about the
2073   software used by the origin server to handle the request. The field
2074   can contain multiple product tokens (&product-tokens;) and comments
2075   identifying the server and any significant subproducts. The product
2076   tokens are listed in order of their significance for identifying the
2077   application.
2079<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2080  <x:ref>Server</x:ref>         = "Server" ":" 1*( <x:ref>product</x:ref> | <x:ref>comment</x:ref> )
2083   Example:
2085<figure><artwork type="example">
2086    Server: CERN/3.0 libwww/2.17
2089   If the response is being forwarded through a proxy, the proxy
2090   application &MUST-NOT; modify the Server response-header. Instead, it
2091   &MUST; include a Via field (as described in &header-via;).
2092  <list><t>
2093      <x:h>Note:</x:h> Revealing the specific software version of the server might
2094      allow the server machine to become more vulnerable to attacks
2095      against software that is known to contain security holes. Server
2096      implementors are encouraged to make this field a configurable
2097      option.
2098  </t></list>
2102<section title="User-Agent" anchor="header.user-agent">
2103  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2104  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2105  <x:anchor-alias value="User-Agent"/>
2107   The User-Agent request-header field contains information about the
2108   user agent originating the request. This is for statistical purposes,
2109   the tracing of protocol violations, and automated recognition of user
2110   agents for the sake of tailoring responses to avoid particular user
2111   agent limitations. User agents &SHOULD; include this field with
2112   requests. The field can contain multiple product tokens (&product-tokens;)
2113   and comments identifying the agent and any subproducts which form a
2114   significant part of the user agent. By convention, the product tokens
2115   are listed in order of their significance for identifying the
2116   application.
2118<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2119  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" 1*( <x:ref>product</x:ref> | <x:ref>comment</x:ref> )
2122   Example:
2124<figure><artwork type="example">
2125    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2131<section title="IANA Considerations" anchor="IANA.considerations">
2133<section title="Method Registry" anchor="method.registration">
2135  The registration procedure for HTTP Methods is defined by
2136  <xref target="method.registry"/> of this document.
2139   The HTTP Method Registry located at <eref target=""/>
2140   should be populated with the registrations below:
2142<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2143<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2144   <ttcol>Method</ttcol>
2145   <ttcol>Safe</ttcol>
2146   <ttcol>Reference</ttcol>
2147   <c>CONNECT</c>
2148   <c>no</c>
2149   <c>
2150      <xref target="CONNECT"/>
2151   </c>
2152   <c>DELETE</c>
2153   <c>no</c>
2154   <c>
2155      <xref target="DELETE"/>
2156   </c>
2157   <c>GET</c>
2158   <c>yes</c>
2159   <c>
2160      <xref target="GET"/>
2161   </c>
2162   <c>HEAD</c>
2163   <c>yes</c>
2164   <c>
2165      <xref target="HEAD"/>
2166   </c>
2167   <c>OPTIONS</c>
2168   <c>yes</c>
2169   <c>
2170      <xref target="OPTIONS"/>
2171   </c>
2172   <c>POST</c>
2173   <c>no</c>
2174   <c>
2175      <xref target="POST"/>
2176   </c>
2177   <c>PUT</c>
2178   <c>no</c>
2179   <c>
2180      <xref target="PUT"/>
2181   </c>
2182   <c>TRACE</c>
2183   <c>yes</c>
2184   <c>
2185      <xref target="TRACE"/>
2186   </c>
2191<section title="Status Code Registry" anchor="status.code.registration">
2193   The registration procedure for HTTP Status Codes -- previously defined
2194   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2195   by <xref target="status.code.registry"/> of this document.
2198   The HTTP Status Code Registry located at <eref target=""/>
2199   should be updated with the registrations below:
2201<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2202<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2203   <ttcol>Value</ttcol>
2204   <ttcol>Description</ttcol>
2205   <ttcol>Reference</ttcol>
2206   <c>100</c>
2207   <c>Continue</c>
2208   <c>
2209      <xref target="status.100"/>
2210   </c>
2211   <c>101</c>
2212   <c>Switching Protocols</c>
2213   <c>
2214      <xref target="status.101"/>
2215   </c>
2216   <c>200</c>
2217   <c>OK</c>
2218   <c>
2219      <xref target="status.200"/>
2220   </c>
2221   <c>201</c>
2222   <c>Created</c>
2223   <c>
2224      <xref target="status.201"/>
2225   </c>
2226   <c>202</c>
2227   <c>Accepted</c>
2228   <c>
2229      <xref target="status.202"/>
2230   </c>
2231   <c>203</c>
2232   <c>Non-Authoritative Information</c>
2233   <c>
2234      <xref target="status.203"/>
2235   </c>
2236   <c>204</c>
2237   <c>No Content</c>
2238   <c>
2239      <xref target="status.204"/>
2240   </c>
2241   <c>205</c>
2242   <c>Reset Content</c>
2243   <c>
2244      <xref target="status.205"/>
2245   </c>
2246   <c>206</c>
2247   <c>Partial Content</c>
2248   <c>
2249      <xref target="status.206"/>
2250   </c>
2251   <c>300</c>
2252   <c>Multiple Choices</c>
2253   <c>
2254      <xref target="status.300"/>
2255   </c>
2256   <c>301</c>
2257   <c>Moved Permanently</c>
2258   <c>
2259      <xref target="status.301"/>
2260   </c>
2261   <c>302</c>
2262   <c>Found</c>
2263   <c>
2264      <xref target="status.302"/>
2265   </c>
2266   <c>303</c>
2267   <c>See Other</c>
2268   <c>
2269      <xref target="status.303"/>
2270   </c>
2271   <c>304</c>
2272   <c>Not Modified</c>
2273   <c>
2274      <xref target="status.304"/>
2275   </c>
2276   <c>305</c>
2277   <c>Use Proxy</c>
2278   <c>
2279      <xref target="status.305"/>
2280   </c>
2281   <c>306</c>
2282   <c>(Unused)</c>
2283   <c>
2284      <xref target="status.306"/>
2285   </c>
2286   <c>307</c>
2287   <c>Temporary Redirect</c>
2288   <c>
2289      <xref target="status.307"/>
2290   </c>
2291   <c>400</c>
2292   <c>Bad Request</c>
2293   <c>
2294      <xref target="status.400"/>
2295   </c>
2296   <c>401</c>
2297   <c>Unauthorized</c>
2298   <c>
2299      <xref target="status.401"/>
2300   </c>
2301   <c>402</c>
2302   <c>Payment Required</c>
2303   <c>
2304      <xref target="status.402"/>
2305   </c>
2306   <c>403</c>
2307   <c>Forbidden</c>
2308   <c>
2309      <xref target="status.403"/>
2310   </c>
2311   <c>404</c>
2312   <c>Not Found</c>
2313   <c>
2314      <xref target="status.404"/>
2315   </c>
2316   <c>405</c>
2317   <c>Method Not Allowed</c>
2318   <c>
2319      <xref target="status.405"/>
2320   </c>
2321   <c>406</c>
2322   <c>Not Acceptable</c>
2323   <c>
2324      <xref target="status.406"/>
2325   </c>
2326   <c>407</c>
2327   <c>Proxy Authentication Required</c>
2328   <c>
2329      <xref target="status.407"/>
2330   </c>
2331   <c>408</c>
2332   <c>Request Timeout</c>
2333   <c>
2334      <xref target="status.408"/>
2335   </c>
2336   <c>409</c>
2337   <c>Conflict</c>
2338   <c>
2339      <xref target="status.409"/>
2340   </c>
2341   <c>410</c>
2342   <c>Gone</c>
2343   <c>
2344      <xref target="status.410"/>
2345   </c>
2346   <c>411</c>
2347   <c>Length Required</c>
2348   <c>
2349      <xref target="status.411"/>
2350   </c>
2351   <c>412</c>
2352   <c>Precondition Failed</c>
2353   <c>
2354      <xref target="status.412"/>
2355   </c>
2356   <c>413</c>
2357   <c>Request Entity Too Large</c>
2358   <c>
2359      <xref target="status.413"/>
2360   </c>
2361   <c>414</c>
2362   <c>Request-URI Too Long</c>
2363   <c>
2364      <xref target="status.414"/>
2365   </c>
2366   <c>415</c>
2367   <c>Unsupported Media Type</c>
2368   <c>
2369      <xref target="status.415"/>
2370   </c>
2371   <c>416</c>
2372   <c>Requested Range Not Satisfiable</c>
2373   <c>
2374      <xref target="status.416"/>
2375   </c>
2376   <c>417</c>
2377   <c>Expectation Failed</c>
2378   <c>
2379      <xref target="status.417"/>
2380   </c>
2381   <c>500</c>
2382   <c>Internal Server Error</c>
2383   <c>
2384      <xref target="status.500"/>
2385   </c>
2386   <c>501</c>
2387   <c>Not Implemented</c>
2388   <c>
2389      <xref target="status.501"/>
2390   </c>
2391   <c>502</c>
2392   <c>Bad Gateway</c>
2393   <c>
2394      <xref target="status.502"/>
2395   </c>
2396   <c>503</c>
2397   <c>Service Unavailable</c>
2398   <c>
2399      <xref target="status.503"/>
2400   </c>
2401   <c>504</c>
2402   <c>Gateway Timeout</c>
2403   <c>
2404      <xref target="status.504"/>
2405   </c>
2406   <c>505</c>
2407   <c>HTTP Version Not Supported</c>
2408   <c>
2409      <xref target="status.505"/>
2410   </c>
2414<section title="Message Header Registration" anchor="message.header.registration">
2416   The Message Header Registry located at <eref target=""/> should be updated
2417   with the permanent registrations below (see <xref target="RFC3864"/>):
2419<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2420<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2421   <ttcol>Header Field Name</ttcol>
2422   <ttcol>Protocol</ttcol>
2423   <ttcol>Status</ttcol>
2424   <ttcol>Reference</ttcol>
2425   <c>Allow</c>
2426   <c>http</c>
2427   <c>standard</c>
2428   <c>
2429      <xref target="header.allow"/>
2430   </c>
2431   <c>Expect</c>
2432   <c>http</c>
2433   <c>standard</c>
2434   <c>
2435      <xref target="header.expect"/>
2436   </c>
2437   <c>From</c>
2438   <c>http</c>
2439   <c>standard</c>
2440   <c>
2441      <xref target="header.from"/>
2442   </c>
2443   <c>Location</c>
2444   <c>http</c>
2445   <c>standard</c>
2446   <c>
2447      <xref target="header.location"/>
2448   </c>
2449   <c>Max-Forwards</c>
2450   <c>http</c>
2451   <c>standard</c>
2452   <c>
2453      <xref target="header.max-forwards"/>
2454   </c>
2455   <c>Referer</c>
2456   <c>http</c>
2457   <c>standard</c>
2458   <c>
2459      <xref target="header.referer"/>
2460   </c>
2461   <c>Retry-After</c>
2462   <c>http</c>
2463   <c>standard</c>
2464   <c>
2465      <xref target="header.retry-after"/>
2466   </c>
2467   <c>Server</c>
2468   <c>http</c>
2469   <c>standard</c>
2470   <c>
2471      <xref target="header.server"/>
2472   </c>
2473   <c>User-Agent</c>
2474   <c>http</c>
2475   <c>standard</c>
2476   <c>
2477      <xref target="header.user-agent"/>
2478   </c>
2482   The change controller is: "IETF ( - Internet Engineering Task Force".
2487<section title="Security Considerations" anchor="security.considerations">
2489   This section is meant to inform application developers, information
2490   providers, and users of the security limitations in HTTP/1.1 as
2491   described by this document. The discussion does not include
2492   definitive solutions to the problems revealed, though it does make
2493   some suggestions for reducing security risks.
2496<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2498   Like any generic data transfer protocol, HTTP cannot regulate the
2499   content of the data that is transferred, nor is there any a priori
2500   method of determining the sensitivity of any particular piece of
2501   information within the context of any given request. Therefore,
2502   applications &SHOULD; supply as much control over this information as
2503   possible to the provider of that information. Four header fields are
2504   worth special mention in this context: Server, Via, Referer and From.
2507   Revealing the specific software version of the server might allow the
2508   server machine to become more vulnerable to attacks against software
2509   that is known to contain security holes. Implementors &SHOULD; make the
2510   Server header field a configurable option.
2513   Proxies which serve as a portal through a network firewall &SHOULD;
2514   take special precautions regarding the transfer of header information
2515   that identifies the hosts behind the firewall. In particular, they
2516   &SHOULD; remove, or replace with sanitized versions, any Via fields
2517   generated behind the firewall.
2520   The Referer header allows reading patterns to be studied and reverse
2521   links drawn. Although it can be very useful, its power can be abused
2522   if user details are not separated from the information contained in
2523   the Referer. Even when the personal information has been removed, the
2524   Referer header might indicate a private document's URI whose
2525   publication would be inappropriate.
2528   The information sent in the From field might conflict with the user's
2529   privacy interests or their site's security policy, and hence it
2530   &SHOULD-NOT;  be transmitted without the user being able to disable,
2531   enable, and modify the contents of the field. The user &MUST; be able
2532   to set the contents of this field within a user preference or
2533   application defaults configuration.
2536   We suggest, though do not require, that a convenient toggle interface
2537   be provided for the user to enable or disable the sending of From and
2538   Referer information.
2541   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2542   fields can sometimes be used to determine that a specific client or
2543   server have a particular security hole which might be exploited.
2544   Unfortunately, this same information is often used for other valuable
2545   purposes for which HTTP currently has no better mechanism.
2549<section title="Encoding Sensitive Information in URIs" anchor="">
2551   Because the source of a link might be private information or might
2552   reveal an otherwise private information source, it is strongly
2553   recommended that the user be able to select whether or not the
2554   Referer field is sent. For example, a browser client could have a
2555   toggle switch for browsing openly/anonymously, which would
2556   respectively enable/disable the sending of Referer and From
2557   information.
2560   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2561   HTTP request if the referring page was transferred with a secure
2562   protocol.
2565   Authors of services should not use
2566   GET-based forms for the submission of sensitive data because that
2567   data will be encoded in the Request-URI. Many existing
2568   servers, proxies, and user agents log or display the Request-URI in
2569   places where it might be visible to third parties. Such services can
2570   use POST-based form submission instead.
2574<section title="Location Headers and Spoofing" anchor="location.spoofing">
2576   If a single server supports multiple organizations that do not trust
2577   one another, then it &MUST; check the values of Location and Content-Location
2578   headers in responses that are generated under control of
2579   said organizations to make sure that they do not attempt to
2580   invalidate resources over which they have no authority.
2586<section title="Acknowledgments" anchor="ack">
2591<references title="Normative References">
2593<reference anchor="Part1">
2594  <front>
2595    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2596    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2597      <organization abbrev="Day Software">Day Software</organization>
2598      <address><email></email></address>
2599    </author>
2600    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2601      <organization>One Laptop per Child</organization>
2602      <address><email></email></address>
2603    </author>
2604    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2605      <organization abbrev="HP">Hewlett-Packard Company</organization>
2606      <address><email></email></address>
2607    </author>
2608    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2609      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2610      <address><email></email></address>
2611    </author>
2612    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2613      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2614      <address><email></email></address>
2615    </author>
2616    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2617      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2618      <address><email></email></address>
2619    </author>
2620    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2621      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2622      <address><email></email></address>
2623    </author>
2624    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2625      <organization abbrev="W3C">World Wide Web Consortium</organization>
2626      <address><email></email></address>
2627    </author>
2628    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2629      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2630      <address><email></email></address>
2631    </author>
2632    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2633  </front>
2634  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2635  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2638<reference anchor="Part3">
2639  <front>
2640    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2641    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2642      <organization abbrev="Day Software">Day Software</organization>
2643      <address><email></email></address>
2644    </author>
2645    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2646      <organization>One Laptop per Child</organization>
2647      <address><email></email></address>
2648    </author>
2649    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2650      <organization abbrev="HP">Hewlett-Packard Company</organization>
2651      <address><email></email></address>
2652    </author>
2653    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2654      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2655      <address><email></email></address>
2656    </author>
2657    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2658      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2659      <address><email></email></address>
2660    </author>
2661    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2662      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2663      <address><email></email></address>
2664    </author>
2665    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2666      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2667      <address><email></email></address>
2668    </author>
2669    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2670      <organization abbrev="W3C">World Wide Web Consortium</organization>
2671      <address><email></email></address>
2672    </author>
2673    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2674      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2675      <address><email></email></address>
2676    </author>
2677    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2678  </front>
2679  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2680  <x:source href="p3-payload.xml" basename="p3-payload"/>
2683<reference anchor="Part4">
2684  <front>
2685    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2686    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2687      <organization abbrev="Day Software">Day Software</organization>
2688      <address><email></email></address>
2689    </author>
2690    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2691      <organization>One Laptop per Child</organization>
2692      <address><email></email></address>
2693    </author>
2694    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2695      <organization abbrev="HP">Hewlett-Packard Company</organization>
2696      <address><email></email></address>
2697    </author>
2698    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2699      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2700      <address><email></email></address>
2701    </author>
2702    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2703      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2704      <address><email></email></address>
2705    </author>
2706    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2707      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2708      <address><email></email></address>
2709    </author>
2710    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2711      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2712      <address><email></email></address>
2713    </author>
2714    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2715      <organization abbrev="W3C">World Wide Web Consortium</organization>
2716      <address><email></email></address>
2717    </author>
2718    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2719      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2720      <address><email></email></address>
2721    </author>
2722    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2723  </front>
2724  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2725  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2728<reference anchor="Part5">
2729  <front>
2730    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2731    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2732      <organization abbrev="Day Software">Day Software</organization>
2733      <address><email></email></address>
2734    </author>
2735    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2736      <organization>One Laptop per Child</organization>
2737      <address><email></email></address>
2738    </author>
2739    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2740      <organization abbrev="HP">Hewlett-Packard Company</organization>
2741      <address><email></email></address>
2742    </author>
2743    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2744      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2745      <address><email></email></address>
2746    </author>
2747    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2748      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2749      <address><email></email></address>
2750    </author>
2751    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2752      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2753      <address><email></email></address>
2754    </author>
2755    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2756      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2757      <address><email></email></address>
2758    </author>
2759    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2760      <organization abbrev="W3C">World Wide Web Consortium</organization>
2761      <address><email></email></address>
2762    </author>
2763    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2764      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2765      <address><email></email></address>
2766    </author>
2767    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2768  </front>
2769  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2770  <x:source href="p5-range.xml" basename="p5-range"/>
2773<reference anchor="Part6">
2774  <front>
2775    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2776    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2777      <organization abbrev="Day Software">Day Software</organization>
2778      <address><email></email></address>
2779    </author>
2780    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2781      <organization>One Laptop per Child</organization>
2782      <address><email></email></address>
2783    </author>
2784    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2785      <organization abbrev="HP">Hewlett-Packard Company</organization>
2786      <address><email></email></address>
2787    </author>
2788    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2789      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2790      <address><email></email></address>
2791    </author>
2792    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2793      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2794      <address><email></email></address>
2795    </author>
2796    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2797      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2798      <address><email></email></address>
2799    </author>
2800    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2801      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2802      <address><email></email></address>
2803    </author>
2804    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2805      <organization abbrev="W3C">World Wide Web Consortium</organization>
2806      <address><email></email></address>
2807    </author>
2808    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2809      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2810      <address><email></email></address>
2811    </author>
2812    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2813  </front>
2814  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2815  <x:source href="p6-cache.xml" basename="p6-cache"/>
2818<reference anchor="Part7">
2819  <front>
2820    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2821    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2822      <organization abbrev="Day Software">Day Software</organization>
2823      <address><email></email></address>
2824    </author>
2825    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2826      <organization>One Laptop per Child</organization>
2827      <address><email></email></address>
2828    </author>
2829    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2830      <organization abbrev="HP">Hewlett-Packard Company</organization>
2831      <address><email></email></address>
2832    </author>
2833    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2834      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2835      <address><email></email></address>
2836    </author>
2837    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2838      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2839      <address><email></email></address>
2840    </author>
2841    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2842      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2843      <address><email></email></address>
2844    </author>
2845    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2846      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2847      <address><email></email></address>
2848    </author>
2849    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2850      <organization abbrev="W3C">World Wide Web Consortium</organization>
2851      <address><email></email></address>
2852    </author>
2853    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2854      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2855      <address><email></email></address>
2856    </author>
2857    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2858  </front>
2859  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2860  <x:source href="p7-auth.xml" basename="p7-auth"/>
2863<reference anchor="RFC2119">
2864  <front>
2865    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2866    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2867      <organization>Harvard University</organization>
2868      <address><email></email></address>
2869    </author>
2870    <date month="March" year="1997"/>
2871  </front>
2872  <seriesInfo name="BCP" value="14"/>
2873  <seriesInfo name="RFC" value="2119"/>
2878<references title="Informative References">
2880<reference anchor="RFC1945">
2881  <front>
2882    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2883    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2884      <organization>MIT, Laboratory for Computer Science</organization>
2885      <address><email></email></address>
2886    </author>
2887    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2888      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2889      <address><email></email></address>
2890    </author>
2891    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2892      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2893      <address><email></email></address>
2894    </author>
2895    <date month="May" year="1996"/>
2896  </front>
2897  <seriesInfo name="RFC" value="1945"/>
2900<reference anchor="RFC2068">
2901  <front>
2902    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2903    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2904      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2905      <address><email></email></address>
2906    </author>
2907    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2908      <organization>MIT Laboratory for Computer Science</organization>
2909      <address><email></email></address>
2910    </author>
2911    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2912      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2913      <address><email></email></address>
2914    </author>
2915    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2916      <organization>MIT Laboratory for Computer Science</organization>
2917      <address><email></email></address>
2918    </author>
2919    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2920      <organization>MIT Laboratory for Computer Science</organization>
2921      <address><email></email></address>
2922    </author>
2923    <date month="January" year="1997"/>
2924  </front>
2925  <seriesInfo name="RFC" value="2068"/>
2928<reference anchor="RFC2616">
2929  <front>
2930    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2931    <author initials="R." surname="Fielding" fullname="R. Fielding">
2932      <organization>University of California, Irvine</organization>
2933      <address><email></email></address>
2934    </author>
2935    <author initials="J." surname="Gettys" fullname="J. Gettys">
2936      <organization>W3C</organization>
2937      <address><email></email></address>
2938    </author>
2939    <author initials="J." surname="Mogul" fullname="J. Mogul">
2940      <organization>Compaq Computer Corporation</organization>
2941      <address><email></email></address>
2942    </author>
2943    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2944      <organization>MIT Laboratory for Computer Science</organization>
2945      <address><email></email></address>
2946    </author>
2947    <author initials="L." surname="Masinter" fullname="L. Masinter">
2948      <organization>Xerox Corporation</organization>
2949      <address><email></email></address>
2950    </author>
2951    <author initials="P." surname="Leach" fullname="P. Leach">
2952      <organization>Microsoft Corporation</organization>
2953      <address><email></email></address>
2954    </author>
2955    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2956      <organization>W3C</organization>
2957      <address><email></email></address>
2958    </author>
2959    <date month="June" year="1999"/>
2960  </front>
2961  <seriesInfo name="RFC" value="2616"/>
2964<reference anchor='RFC2817'>
2965  <front>
2966    <title>Upgrading to TLS Within HTTP/1.1</title>
2967    <author initials='R.' surname='Khare' fullname='R. Khare'>
2968      <organization>4K Associates / UC Irvine</organization>
2969      <address><email></email></address>
2970    </author>
2971    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2972      <organization>Agranat Systems, Inc.</organization>
2973      <address><email></email></address>
2974    </author>
2975    <date year='2000' month='May' />
2976  </front>
2977  <seriesInfo name='RFC' value='2817' />
2980<reference anchor='RFC3864'>
2981  <front>
2982    <title>Registration Procedures for Message Header Fields</title>
2983    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2984      <organization>Nine by Nine</organization>
2985      <address><email></email></address>
2986    </author>
2987    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2988      <organization>BEA Systems</organization>
2989      <address><email></email></address>
2990    </author>
2991    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2992      <organization>HP Labs</organization>
2993      <address><email></email></address>
2994    </author>
2995    <date year='2004' month='September' />
2996  </front>
2997  <seriesInfo name='BCP' value='90' />
2998  <seriesInfo name='RFC' value='3864' />
3001<reference anchor='RFC5226'>
3002  <front>
3003    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3004    <author initials='T.' surname='Narten' fullname='T. Narten'>
3005      <organization>IBM</organization>
3006      <address><email></email></address>
3007    </author>
3008    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3009      <organization>Google</organization>
3010      <address><email></email></address>
3011    </author>
3012    <date year='2008' month='May' />
3013  </front>
3014  <seriesInfo name='BCP' value='26' />
3015  <seriesInfo name='RFC' value='5226' />
3018<reference anchor="RFC5322">
3019  <front>
3020    <title>Internet Message Format</title>
3021    <author initials="P." surname="Resnick" fullname="P. Resnick">
3022      <organization>Qualcomm Incorporated</organization>
3023    </author>
3024    <date year="2008" month="October"/>
3025  </front>
3026  <seriesInfo name="RFC" value="5322"/>
3031<section title="Compatibility with Previous Versions" anchor="compatibility">
3032<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3034   Clarified which error code should be used for inbound server failures
3035   (e.g. DNS failures). (<xref target="status.504"/>).
3038   201 (Created) had a race that required an Etag be sent when a resource is
3039   first created. (<xref target="status.201"/>).
3042   Rewrite of message transmission requirements to make it much harder
3043   for implementors to get it wrong, as the consequences of errors here
3044   can have significant impact on the Internet, and to deal with the
3045   following problems:
3046  <list style="numbers">
3047      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3048         this was incorrectly placing a requirement on the behavior of
3049         an implementation of a future version of HTTP/1.x</t>
3051      <t>Made it clear that user-agents should retry requests, not
3052         "clients" in general.</t>
3054      <t>Converted requirements for clients to ignore unexpected 100
3055         (Continue) responses, and for proxies to forward 100 responses,
3056         into a general requirement for 1xx responses.</t>
3058      <t>Modified some TCP-specific language, to make it clearer that
3059         non-TCP transports are possible for HTTP.</t>
3061      <t>Require that the origin server &MUST-NOT; wait for the request
3062         body before it sends a required 100 (Continue) response.</t>
3064      <t>Allow, rather than require, a server to omit 100 (Continue) if
3065         it has already seen some of the request body.</t>
3067      <t>Allow servers to defend against denial-of-service attacks and
3068         broken clients.</t>
3069  </list>
3072   This change adds the Expect header and 417 status code.
3075   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3076   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3079   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
3080   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3084<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3086  This document takes over the Status Code Registry, previously defined
3087  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3088  (<xref target="status.code.registry"/>)
3091  Clarify definition of POST.
3092  (<xref target="POST"/>)
3095  Failed to consider that there are
3096  many other request methods that are safe to automatically redirect,
3097  and further that the user agent is able to make that determination
3098  based on the request method semantics.
3099  (Sections <xref format="counter" target="status.301"/>,
3100  <xref format="counter" target="status.302"/> and
3101  <xref format="counter" target="status.307"/>)
3104  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3105  It used to indicate that the requested resource must be accessed through the
3106  proxy given by the Location field. The Location field gave the URI of the
3107  proxy. The recipient was expected to repeat this single request via the proxy.
3108  (<xref target="status.305"/>)
3111  Reclassify Allow header as response header, removing the option to
3112  specify it in a PUT request.
3113  Relax the server requirement on the contents of the Allow header and
3114  remove requirement on clients to always trust the header value.
3115  (<xref target="header.allow"/>)
3118  Correct syntax of Location header to allow fragment,
3119  as referred symbol wasn't what was expected, and add some
3120  clarifications as to when it would not be appropriate.
3121  (<xref target="header.location"/>)
3124  In the description of the Server header, the Via field
3125  was described as a SHOULD. The requirement was and is stated
3126  correctly in the description of the Via header in &header-via;.
3127  (<xref target="header.server"/>)
3133<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3135<section title="Since RFC2616">
3137  Extracted relevant partitions from <xref target="RFC2616"/>.
3141<section title="Since draft-ietf-httpbis-p2-semantics-00">
3143  Closed issues:
3144  <list style="symbols">
3145    <t>
3146      <eref target=""/>:
3147      "Via is a MUST"
3148      (<eref target=""/>)
3149    </t>
3150    <t>
3151      <eref target=""/>:
3152      "Fragments allowed in Location"
3153      (<eref target=""/>)
3154    </t>
3155    <t>
3156      <eref target=""/>:
3157      "Safe Methods vs Redirection"
3158      (<eref target=""/>)
3159    </t>
3160    <t>
3161      <eref target=""/>:
3162      "Revise description of the POST method"
3163      (<eref target=""/>)
3164    </t>
3165    <t>
3166      <eref target=""/>:
3167      "Normative and Informative references"
3168    </t>
3169    <t>
3170      <eref target=""/>:
3171      "RFC2606 Compliance"
3172    </t>
3173    <t>
3174      <eref target=""/>:
3175      "Informative references"
3176    </t>
3177    <t>
3178      <eref target=""/>:
3179      "Redundant cross-references"
3180    </t>
3181  </list>
3184  Other changes:
3185  <list style="symbols">
3186    <t>
3187      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3188    </t>
3189  </list>
3193<section title="Since draft-ietf-httpbis-p2-semantics-01">
3195  Closed issues:
3196  <list style="symbols">
3197    <t>
3198      <eref target=""/>:
3199      "PUT side effects"
3200    </t>
3201    <t>
3202      <eref target=""/>:
3203      "Duplicate Host header requirements"
3204    </t>
3205  </list>
3208  Ongoing work on ABNF conversion (<eref target=""/>):
3209  <list style="symbols">
3210    <t>
3211      Move "Product Tokens" section (back) into Part 1, as "token" is used
3212      in the definition of the Upgrade header.
3213    </t>
3214    <t>
3215      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3216    </t>
3217    <t>
3218      Copy definition of delta-seconds from Part6 instead of referencing it.
3219    </t>
3220  </list>
3224<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3226  Closed issues:
3227  <list style="symbols">
3228    <t>
3229      <eref target=""/>:
3230      "Requiring Allow in 405 responses"
3231    </t>
3232    <t>
3233      <eref target=""/>:
3234      "Status Code Registry"
3235    </t>
3236    <t>
3237      <eref target=""/>:
3238      "Redirection vs. Location"
3239    </t>
3240    <t>
3241      <eref target=""/>:
3242      "Cacheability of 303 response"
3243    </t>
3244    <t>
3245      <eref target=""/>:
3246      "305 Use Proxy"
3247    </t>
3248    <t>
3249      <eref target=""/>:
3250      "Classification for Allow header"
3251    </t>
3252    <t>
3253      <eref target=""/>:
3254      "PUT - 'store under' vs 'store at'"
3255    </t>
3256  </list>
3259  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3260  <list style="symbols">
3261    <t>
3262      Reference RFC 3984, and update header registrations for headers defined
3263      in this document.
3264    </t>
3265  </list>
3268  Ongoing work on ABNF conversion (<eref target=""/>):
3269  <list style="symbols">
3270    <t>
3271      Replace string literals when the string really is case-sensitive (method).
3272    </t>
3273  </list>
3277<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3279  Closed issues:
3280  <list style="symbols">
3281    <t>
3282      <eref target=""/>:
3283      "OPTIONS request bodies"
3284    </t>
3285    <t>
3286      <eref target=""/>:
3287      "Description of CONNECT should refer to RFC2817"
3288    </t>
3289    <t>
3290      <eref target=""/>:
3291      "Location Content-Location reference request/response mixup"
3292    </t>
3293  </list>
3296  Ongoing work on Method Registry (<eref target=""/>):
3297  <list style="symbols">
3298    <t>
3299      Added initial proposal for registration process, plus initial
3300      content (non-HTTP/1.1 methods to be added by a separate specification).
3301    </t>
3302  </list>
3306<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3308  Closed issues:
3309  <list style="symbols">
3310    <t>
3311      <eref target=""/>:
3312      "Content-*"
3313    </t>
3314    <t>
3315      <eref target=""/>:
3316      "RFC 2822 is updated by RFC 5322"
3317    </t>
3318  </list>
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