source: draft-ietf-httpbis/latest/p2-semantics.xml @ 371

Last change on this file since 371 was 371, checked in by julian.reschke@…, 14 years ago

Cleanup. (related to #36)

  • Property svn:eol-style set to native
File size: 144.2 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.04"/>.
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"/>
296  <x:anchor-alias value="OWS"/>
297  <x:anchor-alias value="RWS"/>
299  This specification uses the ABNF syntax defined in &notation-abnf; and
300  the core rules defined in &basic-rules;:
301  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
302  <eref target=""/>.</cref>
304<figure><artwork type="abnf2616">
305  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
307<figure><artwork type="abnf2616">
308  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
309  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
310  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
311  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
312  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
314<t anchor="abnf.dependencies">
315  <x:anchor-alias value="absoluteURI"/>
316  <x:anchor-alias value="Accept"/>
317  <x:anchor-alias value="Accept-Charset"/>
318  <x:anchor-alias value="Accept-Encoding"/>
319  <x:anchor-alias value="Accept-Language"/>
320  <x:anchor-alias value="Accept-Ranges"/>
321  <x:anchor-alias value="Age"/>
322  <x:anchor-alias value="Authorization"/>
323  <x:anchor-alias value="ETag"/>
324  <x:anchor-alias value="fragment"/>
325  <x:anchor-alias value="Host"/>
326  <x:anchor-alias value="HTTP-date"/>
327  <x:anchor-alias value="If-Match"/>
328  <x:anchor-alias value="If-Modified-Since"/>
329  <x:anchor-alias value="If-None-Match"/>
330  <x:anchor-alias value="If-Range"/>
331  <x:anchor-alias value="If-Unmodified-Since"/>
332  <x:anchor-alias value="product"/>
333  <x:anchor-alias value="Proxy-Authenticate"/>
334  <x:anchor-alias value="Proxy-Authorization"/>
335  <x:anchor-alias value="Range"/>
336  <x:anchor-alias value="relativeURI"/>
337  <x:anchor-alias value="TE"/>
338  <x:anchor-alias value="Vary"/>
339  <x:anchor-alias value="WWW-Authenticate"/>
340  The ABNF rules below are defined in other parts:
342<figure><!--Part1--><artwork type="abnf2616">
343  <x:ref>absoluteURI</x:ref>   = &lt;absoluteURI, defined in &general-syntax;&gt;
344  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &general-syntax;&gt;
345  <x:ref>Host</x:ref>          = &lt;Host, defined in &header-host;&gt;
346  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
347  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
348  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &general-syntax;&gt;
349  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
351<figure><!--Part3--><artwork type="abnf2616">
352  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
353  <x:ref>Accept-Charset</x:ref> =
354             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
355  <x:ref>Accept-Encoding</x:ref> =
356             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
357  <x:ref>Accept-Language</x:ref> =
358             &lt;Accept-Language, defined in &header-accept-language;&gt;
360<figure><!--Part4--><artwork type="abnf2616">
361  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
362  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
363  <x:ref>If-Modified-Since</x:ref> =
364             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
365  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
366  <x:ref>If-Unmodified-Since</x:ref> =
367             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
369<figure><!--Part5--><artwork type="abnf2616">
370  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
371  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
372  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
374<figure><!--Part6--><artwork type="abnf2616">
375  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
376  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
378<figure><artwork type="abnf2616">
379  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
380  <x:ref>Proxy-Authenticate</x:ref> =
381             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
382  <x:ref>Proxy-Authorization</x:ref> =
383             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
384  <x:ref>WWW-Authenticate</x:ref> =
385             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
389<section title="Method" anchor="method">
390  <x:anchor-alias value="Method"/>
391  <x:anchor-alias value="extension-method"/>
393   The Method  token indicates the method to be performed on the
394   resource identified by the Request-URI. The method is case-sensitive.
396<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
397  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
398                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
399                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
400                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
401                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
402                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
403                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
404                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
405                 / <x:ref>extension-method</x:ref>
406  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
409   The list of methods allowed by a resource can be specified in an
410   Allow header field (<xref target="header.allow"/>). The return code of the response
411   always notifies the client whether a method is currently allowed on a
412   resource, since the set of allowed methods can change dynamically. An
413   origin server &SHOULD; return the status code 405 (Method Not Allowed)
414   if the method is known by the origin server but not allowed for the
415   requested resource, and 501 (Not Implemented) if the method is
416   unrecognized or not implemented by the origin server. The methods GET
417   and HEAD &MUST; be supported by all general-purpose servers. All other
418   methods are &OPTIONAL;; however, if the above methods are implemented,
419   they &MUST; be implemented with the same semantics as those specified
420   in <xref target="method.definitions"/>.
423<section title="Method Registry" anchor="method.registry">
425  The HTTP Method Registry defines the name space for the Method token in the
426  Request line of an HTTP request.
429  Registrations &MUST; include the following fields:
430  <list style="symbols">
431    <t>Method Name (see <xref target="method"/>)</t>
432    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
433    <t>Pointer to specification text</t>
434  </list>
437  Values to be added to this name space are subject to IETF review
438  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
439  new method names should be traceable through statuses of either 'Obsoletes'
440  or 'Updates' to this document.
443  The registry itself is maintained at <eref target=""/>.
448<section title="Request Header Fields" anchor="request.header.fields">
449  <x:anchor-alias value="extension-code"/>
450  <x:anchor-alias value="request-header"/>
452   The request-header fields allow the client to pass additional
453   information about the request, and about the client itself, to the
454   server. These fields act as request modifiers, with semantics
455   equivalent to the parameters on a programming language method
456   invocation.
458<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
459  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
460                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
461                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
462                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
463                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
464                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
465                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
466                 / <x:ref>Host</x:ref>                     ; &header-host;
467                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
468                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
469                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
470                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
471                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
472                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
473                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
474                 / <x:ref>Range</x:ref>                    ; &header-range;
475                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
476                 / <x:ref>TE</x:ref>                       ; &header-te;
477                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
480   Request-header field names can be extended reliably only in
481   combination with a change in the protocol version. However, new or
482   experimental header fields &MAY; be given the semantics of request-header
483   fields if all parties in the communication recognize them to
484   be request-header fields. Unrecognized header fields are treated as
485   entity-header fields.
489<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
490  <x:anchor-alias value="Reason-Phrase"/>
491  <x:anchor-alias value="Status-Code"/>
493   The Status-Code element is a 3-digit integer result code of the
494   attempt to understand and satisfy the request. The status codes listed
495   below are defined in <xref target=""/>.
496   The Reason-Phrase is intended to give a short
497   textual description of the Status-Code. The Status-Code is intended
498   for use by automata and the Reason-Phrase is intended for the human
499   user. The client is not required to examine or display the Reason-Phrase.
502   The individual values of the numeric status codes defined for
503   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
504   presented below. The reason phrases listed here are only
505   recommendations -- they &MAY; be replaced by local equivalents without
506   affecting the protocol.
508<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"/>
509  <x:ref>Status-Code</x:ref>    =
510         "100"  ; <xref target="status.100"/>: Continue
511       / "101"  ; <xref target="status.101"/>: Switching Protocols
512       / "200"  ; <xref target="status.200"/>: OK
513       / "201"  ; <xref target="status.201"/>: Created
514       / "202"  ; <xref target="status.202"/>: Accepted
515       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
516       / "204"  ; <xref target="status.204"/>: No Content
517       / "205"  ; <xref target="status.205"/>: Reset Content
518       / "206"  ; <xref target="status.206"/>: Partial Content
519       / "300"  ; <xref target="status.300"/>: Multiple Choices
520       / "301"  ; <xref target="status.301"/>: Moved Permanently
521       / "302"  ; <xref target="status.302"/>: Found
522       / "303"  ; <xref target="status.303"/>: See Other
523       / "304"  ; <xref target="status.304"/>: Not Modified
524       / "305"  ; <xref target="status.305"/>: Use Proxy
525       / "307"  ; <xref target="status.307"/>: Temporary Redirect
526       / "400"  ; <xref target="status.400"/>: Bad Request
527       / "401"  ; <xref target="status.401"/>: Unauthorized
528       / "402"  ; <xref target="status.402"/>: Payment Required
529       / "403"  ; <xref target="status.403"/>: Forbidden
530       / "404"  ; <xref target="status.404"/>: Not Found
531       / "405"  ; <xref target="status.405"/>: Method Not Allowed
532       / "406"  ; <xref target="status.406"/>: Not Acceptable
533       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
534       / "408"  ; <xref target="status.408"/>: Request Time-out
535       / "409"  ; <xref target="status.409"/>: Conflict
536       / "410"  ; <xref target="status.410"/>: Gone
537       / "411"  ; <xref target="status.411"/>: Length Required
538       / "412"  ; <xref target="status.412"/>: Precondition Failed
539       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
540       / "414"  ; <xref target="status.414"/>: Request-URI Too Large
541       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
542       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
543       / "417"  ; <xref target="status.417"/>: Expectation Failed
544       / "500"  ; <xref target="status.500"/>: Internal Server Error
545       / "501"  ; <xref target="status.501"/>: Not Implemented
546       / "502"  ; <xref target="status.502"/>: Bad Gateway
547       / "503"  ; <xref target="status.503"/>: Service Unavailable
548       / "504"  ; <xref target="status.504"/>: Gateway Time-out
549       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
550       / <x:ref>extension-code</x:ref>
552  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
553  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
556   HTTP status codes are extensible. HTTP applications are not required
557   to understand the meaning of all registered status codes, though such
558   understanding is obviously desirable. However, applications &MUST;
559   understand the class of any status code, as indicated by the first
560   digit, and treat any unrecognized response as being equivalent to the
561   x00 status code of that class, with the exception that an
562   unrecognized response &MUST-NOT; be cached. For example, if an
563   unrecognized status code of 431 is received by the client, it can
564   safely assume that there was something wrong with its request and
565   treat the response as if it had received a 400 status code. In such
566   cases, user agents &SHOULD; present to the user the entity returned
567   with the response, since that entity is likely to include human-readable
568   information which will explain the unusual status.
571<section title="Status Code Registry" anchor="status.code.registry">
573  The HTTP Status Code Registry defines the name space for the Status-Code
574  token in the Status line of an HTTP response.
577  Values to be added to this name space are subject to IETF review
578  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
579  new status codes should be traceable through statuses of either 'Obsoletes'
580  or 'Updates' to this document.
583  The registry itself is maintained at <eref target=""/>.
589<section title="Response Header Fields" anchor="response.header.fields">
590  <x:anchor-alias value="response-header"/>
592   The response-header fields allow the server to pass additional
593   information about the response which cannot be placed in the Status-Line.
594   These header fields give information about the server and about
595   further access to the resource identified by the Request-URI.
597<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
598  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
599                  / <x:ref>Age</x:ref>                     ; &header-age;
600                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
601                  / <x:ref>ETag</x:ref>                    ; &header-etag;
602                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
603                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
604                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
605                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
606                  / <x:ref>Vary</x:ref>                    ; &header-vary;
607                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
610   Response-header field names can be extended reliably only in
611   combination with a change in the protocol version. However, new or
612   experimental header fields &MAY; be given the semantics of response-header
613   fields if all parties in the communication recognize them to
614   be response-header fields. Unrecognized header fields are treated as
615   entity-header fields.
619<section title="Entity" anchor="entity">
621   Request and Response messages &MAY; transfer an entity if not otherwise
622   restricted by the request method or response status code. An entity
623   consists of entity-header fields and an entity-body, although some
624   responses will only include the entity-headers. HTTP entity-body and
625   entity-header fields are defined in &payload;.
628   An entity-body is only present in a message when a message-body is
629   present, as described in &message-body;. The entity-body is obtained
630   from the message-body by decoding any Transfer-Encoding that might
631   have been applied to ensure safe and proper transfer of the message.
636<section title="Method Definitions" anchor="method.definitions">
638   The set of common methods for HTTP/1.1 is defined below. Although
639   this set can be expanded, additional methods cannot be assumed to
640   share the same semantics for separately extended clients and servers.
643<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
645<section title="Safe Methods" anchor="safe.methods">
646<iref item="Safe Methods" primary="true"/>
648   Implementors should be aware that the software represents the user in
649   their interactions over the Internet, and should be careful to allow
650   the user to be aware of any actions they might take which may have an
651   unexpected significance to themselves or others.
654   In particular, the convention has been established that the GET and
655   HEAD methods &SHOULD-NOT;  have the significance of taking an action
656   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
657   This allows user agents to represent other methods, such as POST, PUT
658   and DELETE, in a special way, so that the user is made aware of the
659   fact that a possibly unsafe action is being requested.
662   Naturally, it is not possible to ensure that the server does not
663   generate side-effects as a result of performing a GET request; in
664   fact, some dynamic resources consider that a feature. The important
665   distinction here is that the user did not request the side-effects,
666   so therefore cannot be held accountable for them.
670<section title="Idempotent Methods" anchor="idempotent.methods">
671<iref item="Idempotent Methods" primary="true"/>
673   Methods can also have the property of "idempotence" in that (aside
674   from error or expiration issues) the side-effects of N &gt; 0 identical
675   requests is the same as for a single request. The methods GET, HEAD,
676   PUT and DELETE share this property. Also, the methods OPTIONS and
677   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
680   However, it is possible that a sequence of several requests is non-idempotent,
681   even if all of the methods executed in that sequence are
682   idempotent. (A sequence is idempotent if a single execution of the
683   entire sequence always yields a result that is not changed by a
684   reexecution of all, or part, of that sequence.) For example, a
685   sequence is non-idempotent if its result depends on a value that is
686   later modified in the same sequence.
689   A sequence that never has side effects is idempotent, by definition
690   (provided that no concurrent operations are being executed on the
691   same set of resources).
696<section title="OPTIONS" anchor="OPTIONS">
697  <rdf:Description>
698    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
699  </rdf:Description>
700  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
701  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
703   The OPTIONS method represents a request for information about the
704   communication options available on the request/response chain
705   identified by the Request-URI. This method allows the client to
706   determine the options and/or requirements associated with a resource,
707   or the capabilities of a server, without implying a resource action
708   or initiating a resource retrieval.
711   Responses to this method are not cacheable.
714   If the OPTIONS request includes an entity-body (as indicated by the
715   presence of Content-Length or Transfer-Encoding), then the media type
716   &MUST; be indicated by a Content-Type field. Although this
717   specification does not define any use for such a body, future
718   extensions to HTTP might use the OPTIONS body to make more detailed
719   queries on the server.
722   If the Request-URI is an asterisk ("*"), the OPTIONS request is
723   intended to apply to the server in general rather than to a specific
724   resource. Since a server's communication options typically depend on
725   the resource, the "*" request is only useful as a "ping" or "no-op"
726   type of method; it does nothing beyond allowing the client to test
727   the capabilities of the server. For example, this can be used to test
728   a proxy for HTTP/1.1 compliance (or lack thereof).
731   If the Request-URI is not an asterisk, the OPTIONS request applies
732   only to the options that are available when communicating with that
733   resource.
736   A 200 response &SHOULD; include any header fields that indicate
737   optional features implemented by the server and applicable to that
738   resource (e.g., Allow), possibly including extensions not defined by
739   this specification. The response body, if any, &SHOULD; also include
740   information about the communication options. The format for such a
741   body is not defined by this specification, but might be defined by
742   future extensions to HTTP. Content negotiation &MAY; be used to select
743   the appropriate response format. If no response body is included, the
744   response &MUST; include a Content-Length field with a field-value of
745   "0".
748   The Max-Forwards request-header field &MAY; be used to target a
749   specific proxy in the request chain. When a proxy receives an OPTIONS
750   request on an absoluteURI for which request forwarding is permitted,
751   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
752   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
753   instead, the proxy &SHOULD; respond with its own communication options.
754   If the Max-Forwards field-value is an integer greater than zero, the
755   proxy &MUST; decrement the field-value when it forwards the request. If
756   no Max-Forwards field is present in the request, then the forwarded
757   request &MUST-NOT; include a Max-Forwards field.
761<section title="GET" anchor="GET">
762  <rdf:Description>
763    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
764  </rdf:Description>
765  <iref primary="true" item="GET method" x:for-anchor=""/>
766  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
768   The GET method means retrieve whatever information (in the form of an
769   entity) is identified by the Request-URI. If the Request-URI refers
770   to a data-producing process, it is the produced data which shall be
771   returned as the entity in the response and not the source text of the
772   process, unless that text happens to be the output of the process.
775   The semantics of the GET method change to a "conditional GET" if the
776   request message includes an If-Modified-Since, If-Unmodified-Since,
777   If-Match, If-None-Match, or If-Range header field. A conditional GET
778   method requests that the entity be transferred only under the
779   circumstances described by the conditional header field(s). The
780   conditional GET method is intended to reduce unnecessary network
781   usage by allowing cached entities to be refreshed without requiring
782   multiple requests or transferring data already held by the client.
785   The semantics of the GET method change to a "partial GET" if the
786   request message includes a Range header field. A partial GET requests
787   that only part of the entity be transferred, as described in &header-range;.
788   The partial GET method is intended to reduce unnecessary
789   network usage by allowing partially-retrieved entities to be
790   completed without transferring data already held by the client.
793   The response to a GET request is cacheable if and only if it meets
794   the requirements for HTTP caching described in &caching;.
797   See <xref target=""/> for security considerations when used for forms.
801<section title="HEAD" anchor="HEAD">
802  <rdf:Description>
803    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
804  </rdf:Description>
805  <iref primary="true" item="HEAD method" x:for-anchor=""/>
806  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
808   The HEAD method is identical to GET except that the server &MUST-NOT;
809   return a message-body in the response. The metainformation contained
810   in the HTTP headers in response to a HEAD request &SHOULD; be identical
811   to the information sent in response to a GET request. This method can
812   be used for obtaining metainformation about the entity implied by the
813   request without transferring the entity-body itself. This method is
814   often used for testing hypertext links for validity, accessibility,
815   and recent modification.
818   The response to a HEAD request &MAY; be cacheable in the sense that the
819   information contained in the response &MAY; be used to update a
820   previously cached entity from that resource. If the new field values
821   indicate that the cached entity differs from the current entity (as
822   would be indicated by a change in Content-Length, Content-MD5, ETag
823   or Last-Modified), then the cache &MUST; treat the cache entry as
824   stale.
828<section title="POST" anchor="POST">
829  <iref primary="true" item="POST method" x:for-anchor=""/>
830  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
832   The POST method is used to request that the origin server accept the
833   entity enclosed in the request as data to be processed by the resource
834   identified by the Request-URI in the Request-Line. POST is designed
835   to allow a uniform method to cover the following functions:
836  <list style="symbols">
837    <t>
838      Annotation of existing resources;
839    </t>
840    <t>
841        Posting a message to a bulletin board, newsgroup, mailing list,
842        or similar group of articles;
843    </t>
844    <t>
845        Providing a block of data, such as the result of submitting a
846        form, to a data-handling process;
847    </t>
848    <t>
849        Extending a database through an append operation.
850    </t>
851  </list>
854   The actual function performed by the POST method is determined by the
855   server and is usually dependent on the Request-URI.
858   The action performed by the POST method might not result in a
859   resource that can be identified by a URI. In this case, either 200
860   (OK) or 204 (No Content) is the appropriate response status,
861   depending on whether or not the response includes an entity that
862   describes the result.
865   If a resource has been created on the origin server, the response
866   &SHOULD; be 201 (Created) and contain an entity which describes the
867   status of the request and refers to the new resource, and a Location
868   header (see <xref target="header.location"/>).
871   Responses to this method are not cacheable, unless the response
872   includes appropriate Cache-Control or Expires header fields. However,
873   the 303 (See Other) response can be used to direct the user agent to
874   retrieve a cacheable resource.
878<section title="PUT" anchor="PUT">
879  <iref primary="true" item="PUT method" x:for-anchor=""/>
880  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
882   The PUT method requests that the enclosed entity be stored at the
883   supplied Request-URI. If the Request-URI refers to an already
884   existing resource, the enclosed entity &SHOULD; be considered as a
885   modified version of the one residing on the origin server. If the
886   Request-URI does not point to an existing resource, and that URI is
887   capable of being defined as a new resource by the requesting user
888   agent, the origin server can create the resource with that URI. If a
889   new resource is created at the Request-URI, the origin server &MUST;
890         inform the user agent
891   via the 201 (Created) response. If an existing resource is modified,
892   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
893   to indicate successful completion of the request. If the resource
894   could not be created or modified with the Request-URI, an appropriate
895   error response &SHOULD; be given that reflects the nature of the
896   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
897   headers (headers starting with the prefix 'Content-') that it does
898   not understand or implement
899   and &MUST; return a 501 (Not Implemented) response in such cases.
902   If the request passes through a cache and the Request-URI identifies
903   one or more currently cached entities, those entries &SHOULD; be
904   treated as stale. Responses to this method are not cacheable.
907   The fundamental difference between the POST and PUT requests is
908   reflected in the different meaning of the Request-URI. The URI in a
909   POST request identifies the resource that will handle the enclosed
910   entity. That resource might be a data-accepting process, a gateway to
911   some other protocol, or a separate entity that accepts annotations.
912   In contrast, the URI in a PUT request identifies the entity enclosed
913   with the request -- the user agent knows what URI is intended and the
914   server &MUST-NOT; attempt to apply the request to some other resource.
915   If the server desires that the request be applied to a different URI,
916   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
917   then make its own decision regarding whether or not to redirect the
918   request.
921   A single resource &MAY; be identified by many different URIs. For
922   example, an article might have a URI for identifying "the current
923   version" which is separate from the URI identifying each particular
924   version. In this case, a PUT request on a general URI might result in
925   several other URIs being defined by the origin server.
928   HTTP/1.1 does not define how a PUT method affects the state of an
929   origin server.
932   Unless otherwise specified for a particular entity-header, the
933   entity-headers in the PUT request &SHOULD; be applied to the resource
934   created or modified by the PUT.
938<section title="DELETE" anchor="DELETE">
939  <iref primary="true" item="DELETE method" x:for-anchor=""/>
940  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
942   The DELETE method requests that the origin server delete the resource
943   identified by the Request-URI. This method &MAY; be overridden by human
944   intervention (or other means) on the origin server. The client cannot
945   be guaranteed that the operation has been carried out, even if the
946   status code returned from the origin server indicates that the action
947   has been completed successfully. However, the server &SHOULD-NOT;
948   indicate success unless, at the time the response is given, it
949   intends to delete the resource or move it to an inaccessible
950   location.
953   A successful response &SHOULD; be 200 (OK) if the response includes an
954   entity describing the status, 202 (Accepted) if the action has not
955   yet been enacted, or 204 (No Content) if the action has been enacted
956   but the response does not include an entity.
959   If the request passes through a cache and the Request-URI identifies
960   one or more currently cached entities, those entries &SHOULD; be
961   treated as stale. Responses to this method are not cacheable.
965<section title="TRACE" anchor="TRACE">
966  <rdf:Description>
967    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
968  </rdf:Description>
969  <iref primary="true" item="TRACE method" x:for-anchor=""/>
970  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
972   The TRACE method is used to invoke a remote, application-layer loop-back
973   of the request message. The final recipient of the request
974   &SHOULD; reflect the message received back to the client as the
975   entity-body of a 200 (OK) response. The final recipient is either the
976   origin server or the first proxy or gateway to receive a Max-Forwards
977   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
978   &MUST-NOT; include an entity.
981   TRACE allows the client to see what is being received at the other
982   end of the request chain and use that data for testing or diagnostic
983   information. The value of the Via header field (&header-via;) is of
984   particular interest, since it acts as a trace of the request chain.
985   Use of the Max-Forwards header field allows the client to limit the
986   length of the request chain, which is useful for testing a chain of
987   proxies forwarding messages in an infinite loop.
990   If the request is valid, the response &SHOULD; contain the entire
991   request message in the entity-body, with a Content-Type of
992   "message/http" (see &media-type-message-http;). Responses to this method
993   &MUST-NOT; be cached.
997<section title="CONNECT" anchor="CONNECT">
998  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
999  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1001   This specification reserves the method name CONNECT for use with a
1002   proxy that can dynamically switch to being a tunnel (e.g. SSL
1003   tunneling <xref target="RFC2817"/>).
1009<section title="Status Code Definitions" anchor="">
1011   Each Status-Code is described below, including a description of which
1012   method(s) it can follow and any metainformation required in the
1013   response.
1016<section title="Informational 1xx" anchor="status.1xx">
1018   This class of status code indicates a provisional response,
1019   consisting only of the Status-Line and optional headers, and is
1020   terminated by an empty line. There are no required headers for this
1021   class of status code. Since HTTP/1.0 did not define any 1xx status
1022   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1023   except under experimental conditions.
1026   A client &MUST; be prepared to accept one or more 1xx status responses
1027   prior to a regular response, even if the client does not expect a 100
1028   (Continue) status message. Unexpected 1xx status responses &MAY; be
1029   ignored by a user agent.
1032   Proxies &MUST; forward 1xx responses, unless the connection between the
1033   proxy and its client has been closed, or unless the proxy itself
1034   requested the generation of the 1xx response. (For example, if a
1035   proxy adds a "Expect: 100-continue" field when it forwards a request,
1036   then it need not forward the corresponding 100 (Continue)
1037   response(s).)
1040<section title="100 Continue" anchor="status.100">
1041  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1042  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1044   The client &SHOULD; continue with its request. This interim response is
1045   used to inform the client that the initial part of the request has
1046   been received and has not yet been rejected by the server. The client
1047   &SHOULD; continue by sending the remainder of the request or, if the
1048   request has already been completed, ignore this response. The server
1049   &MUST; send a final response after the request has been completed. See
1050   &use100; for detailed discussion of the use and handling of this
1051   status code.
1055<section title="101 Switching Protocols" anchor="status.101">
1056  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1057  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1059   The server understands and is willing to comply with the client's
1060   request, via the Upgrade message header field (&header-upgrade;), for a
1061   change in the application protocol being used on this connection. The
1062   server will switch protocols to those defined by the response's
1063   Upgrade header field immediately after the empty line which
1064   terminates the 101 response.
1067   The protocol &SHOULD; be switched only when it is advantageous to do
1068   so. For example, switching to a newer version of HTTP is advantageous
1069   over older versions, and switching to a real-time, synchronous
1070   protocol might be advantageous when delivering resources that use
1071   such features.
1076<section title="Successful 2xx" anchor="status.2xx">
1078   This class of status code indicates that the client's request was
1079   successfully received, understood, and accepted.
1082<section title="200 OK" anchor="status.200">
1083  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1084  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1086   The request has succeeded. The information returned with the response
1087   is dependent on the method used in the request, for example:
1088  <list style="hanging">
1089    <t hangText="GET">
1090          an entity corresponding to the requested resource is sent in
1091          the response;
1092    </t>
1093    <t hangText="HEAD">
1094          the entity-header fields corresponding to the requested
1095          resource are sent in the response without any message-body;
1096    </t>
1097    <t hangText="POST">
1098      an entity describing or containing the result of the action;
1099    </t>
1100    <t hangText="TRACE">
1101      an entity containing the request message as received by the
1102      end server.
1103    </t>
1104  </list>
1108<section title="201 Created" anchor="status.201">
1109  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1110  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1112   The request has been fulfilled and resulted in a new resource being
1113   created. The newly created resource can be referenced by the URI(s)
1114   returned in the entity of the response, with the most specific URI
1115   for the resource given by a Location header field. The response
1116   &SHOULD; include an entity containing a list of resource
1117   characteristics and location(s) from which the user or user agent can
1118   choose the one most appropriate. The entity format is specified by
1119   the media type given in the Content-Type header field. The origin
1120   server &MUST; create the resource before returning the 201 status code.
1121   If the action cannot be carried out immediately, the server &SHOULD;
1122   respond with 202 (Accepted) response instead.
1125   A 201 response &MAY; contain an ETag response header field indicating
1126   the current value of the entity tag for the requested variant just
1127   created, see &header-etag;.
1131<section title="202 Accepted" anchor="status.202">
1132  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1133  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1135   The request has been accepted for processing, but the processing has
1136   not been completed.  The request might or might not eventually be
1137   acted upon, as it might be disallowed when processing actually takes
1138   place. There is no facility for re-sending a status code from an
1139   asynchronous operation such as this.
1142   The 202 response is intentionally non-committal. Its purpose is to
1143   allow a server to accept a request for some other process (perhaps a
1144   batch-oriented process that is only run once per day) without
1145   requiring that the user agent's connection to the server persist
1146   until the process is completed. The entity returned with this
1147   response &SHOULD; include an indication of the request's current status
1148   and either a pointer to a status monitor or some estimate of when the
1149   user can expect the request to be fulfilled.
1153<section title="203 Non-Authoritative Information" anchor="status.203">
1154  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1155  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1157   The returned metainformation in the entity-header is not the
1158   definitive set as available from the origin server, but is gathered
1159   from a local or a third-party copy. The set presented &MAY; be a subset
1160   or superset of the original version. For example, including local
1161   annotation information about the resource might result in a superset
1162   of the metainformation known by the origin server. Use of this
1163   response code is not required and is only appropriate when the
1164   response would otherwise be 200 (OK).
1168<section title="204 No Content" anchor="status.204">
1169  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1170  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1172   The server has fulfilled the request but does not need to return an
1173   entity-body, and might want to return updated metainformation. The
1174   response &MAY; include new or updated metainformation in the form of
1175   entity-headers, which if present &SHOULD; be associated with the
1176   requested variant.
1179   If the client is a user agent, it &SHOULD-NOT;  change its document view
1180   from that which caused the request to be sent. This response is
1181   primarily intended to allow input for actions to take place without
1182   causing a change to the user agent's active document view, although
1183   any new or updated metainformation &SHOULD; be applied to the document
1184   currently in the user agent's active view.
1187   The 204 response &MUST-NOT; include a message-body, and thus is always
1188   terminated by the first empty line after the header fields.
1192<section title="205 Reset Content" anchor="status.205">
1193  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1194  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1196   The server has fulfilled the request and the user agent &SHOULD; reset
1197   the document view which caused the request to be sent. This response
1198   is primarily intended to allow input for actions to take place via
1199   user input, followed by a clearing of the form in which the input is
1200   given so that the user can easily initiate another input action. The
1201   response &MUST-NOT; include an entity.
1205<section title="206 Partial Content" anchor="status.206">
1206  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1207  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1209   The server has fulfilled the partial GET request for the resource
1210   and the enclosed entity is a partial representation as defined in &range;.
1215<section title="Redirection 3xx" anchor="status.3xx">
1217   This class of status code indicates that further action needs to be
1218   taken by the user agent in order to fulfill the request.  The action
1219   required &MAY; be carried out by the user agent without interaction
1220   with the user if and only if the method used in the second request is
1221   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1222   such loops generate network traffic for each redirection.
1223  <list><t>
1224      <x:h>Note:</x:h> previous versions of this specification recommended a
1225      maximum of five redirections. Content developers should be aware
1226      that there might be clients that implement such a fixed
1227      limitation.
1228  </t></list>
1231<section title="300 Multiple Choices" anchor="status.300">
1232  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1233  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1235   The requested resource corresponds to any one of a set of
1236   representations, each with its own specific location, and agent-driven
1237   negotiation information (&content-negotiation;) is being provided so that
1238   the user (or user agent) can select a preferred representation and
1239   redirect its request to that location.
1242   Unless it was a HEAD request, the response &SHOULD; include an entity
1243   containing a list of resource characteristics and location(s) from
1244   which the user or user agent can choose the one most appropriate. The
1245   entity format is specified by the media type given in the Content-Type
1246   header field. Depending upon the format and the capabilities of
1247   the user agent, selection of the most appropriate choice &MAY; be
1248   performed automatically. However, this specification does not define
1249   any standard for such automatic selection.
1252   If the server has a preferred choice of representation, it &SHOULD;
1253   include the specific URI for that representation in the Location
1254   field; user agents &MAY; use the Location field value for automatic
1255   redirection. This response is cacheable unless indicated otherwise.
1259<section title="301 Moved Permanently" anchor="status.301">
1260  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1261  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1263   The requested resource has been assigned a new permanent URI and any
1264   future references to this resource &SHOULD; use one of the returned
1265   URIs.  Clients with link editing capabilities ought to automatically
1266   re-link references to the Request-URI to one or more of the new
1267   references returned by the server, where possible. This response is
1268   cacheable unless indicated otherwise.
1271   The new permanent URI &SHOULD; be given by the Location field in the
1272   response. Unless the request method was HEAD, the entity of the
1273   response &SHOULD; contain a short hypertext note with a hyperlink to
1274   the new URI(s).
1277   If the 301 status code is received in response to a request method
1278   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1279   then the request &MAY; be automatically redirected by the user agent without
1280   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1281   request unless it can be confirmed by the user, since this might
1282   change the conditions under which the request was issued.
1283  <list><t>
1284      <x:h>Note:</x:h> When automatically redirecting a POST request after
1285      receiving a 301 status code, some existing HTTP/1.0 user agents
1286      will erroneously change it into a GET request.
1287  </t></list>
1291<section title="302 Found" anchor="status.302">
1292  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1293  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1295   The requested resource resides temporarily under a different URI.
1296   Since the redirection might be altered on occasion, the client &SHOULD;
1297   continue to use the Request-URI for future requests.  This response
1298   is only cacheable if indicated by a Cache-Control or Expires header
1299   field.
1302   The temporary URI &SHOULD; be given by the Location field in the
1303   response. Unless the request method was HEAD, the entity of the
1304   response &SHOULD; contain a short hypertext note with a hyperlink to
1305   the new URI(s).
1308   If the 302 status code is received in response to a request method
1309   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1310   then the request &MAY; be automatically redirected by the user agent without
1311   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1312   request unless it can be confirmed by the user, since this might
1313   change the conditions under which the request was issued.
1314  <list><t>
1315      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1316      to change the method on the redirected request.  However, most
1317      existing user agent implementations treat 302 as if it were a 303
1318      response, performing a GET on the Location field-value regardless
1319      of the original request method. The status codes 303 and 307 have
1320      been added for servers that wish to make unambiguously clear which
1321      kind of reaction is expected of the client.
1322  </t></list>
1326<section title="303 See Other" anchor="status.303">
1327  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1328  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1330   The server directs the user agent to a different resource, indicated
1331   by a URI in the Location header field, that provides an indirect
1332   response to the original request.  The user agent &MAY; perform a GET
1333   request on the URI in the Location field in order to obtain a
1334   representation corresponding to the response, be redirected again,
1335   or end with an error status.  The Location URI is not a substitute
1336   reference for the originally requested resource.
1339   The 303 status is generally applicable to any HTTP method.  It is
1340   primarily used to allow the output of a POST action to redirect
1341   the user agent to a selected resource, since doing so provides the
1342   information corresponding to the POST response in a form that
1343   can be separately identified, bookmarked, and cached independent
1344   of the original request.
1347   A 303 response to a GET request indicates that the requested
1348   resource does not have a representation of its own that can be
1349   transferred by the server over HTTP.  The Location URI indicates a
1350   resource that is descriptive of the requested resource such that
1351   the follow-on representation may be useful without implying that
1352   it adequately represents the previously requested resource.
1353   Note that answers to the questions of what can be represented, what
1354   representations are adequate, and what might be a useful description
1355   are outside the scope of HTTP and thus entirely determined by the
1356   resource owner(s).
1359   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1360   cacheable by Cache-Control or Expires header fields.  Except for
1361   responses to a HEAD request, the entity of a 303 response &SHOULD;
1362   contain a short hypertext note with a hyperlink to the Location URI.
1366<section title="304 Not Modified" anchor="status.304">
1367  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1368  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1370   The response to the request has not been modified since the conditions
1371   indicated by the client's conditional GET request, as defined in &conditional;.
1375<section title="305 Use Proxy" anchor="status.305">
1376  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1377  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1379   The 305 status was defined in a previous version of this specification
1380   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1384<section title="306 (Unused)" anchor="status.306">
1385  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1386  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1388   The 306 status code was used in a previous version of the
1389   specification, is no longer used, and the code is reserved.
1393<section title="307 Temporary Redirect" anchor="status.307">
1394  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1395  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1397   The requested resource resides temporarily under a different URI.
1398   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1399   continue to use the Request-URI for future requests.  This response
1400   is only cacheable if indicated by a Cache-Control or Expires header
1401   field.
1404   The temporary URI &SHOULD; be given by the Location field in the
1405   response. Unless the request method was HEAD, the entity of the
1406   response &SHOULD; contain a short hypertext note with a hyperlink to
1407   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1408   understand the 307 status. Therefore, the note &SHOULD; contain the
1409   information necessary for a user to repeat the original request on
1410   the new URI.
1413   If the 307 status code is received in response to a request method
1414   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1415   then the request &MAY; be automatically redirected by the user agent without
1416   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1417   request unless it can be confirmed by the user, since this might
1418   change the conditions under which the request was issued.
1423<section title="Client Error 4xx" anchor="status.4xx">
1425   The 4xx class of status code is intended for cases in which the
1426   client seems to have erred. Except when responding to a HEAD request,
1427   the server &SHOULD; include an entity containing an explanation of the
1428   error situation, and whether it is a temporary or permanent
1429   condition. These status codes are applicable to any request method.
1430   User agents &SHOULD; display any included entity to the user.
1433   If the client is sending data, a server implementation using TCP
1434   &SHOULD; be careful to ensure that the client acknowledges receipt of
1435   the packet(s) containing the response, before the server closes the
1436   input connection. If the client continues sending data to the server
1437   after the close, the server's TCP stack will send a reset packet to
1438   the client, which may erase the client's unacknowledged input buffers
1439   before they can be read and interpreted by the HTTP application.
1442<section title="400 Bad Request" anchor="status.400">
1443  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1444  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1446   The request could not be understood by the server due to malformed
1447   syntax. The client &SHOULD-NOT;  repeat the request without
1448   modifications.
1452<section title="401 Unauthorized" anchor="status.401">
1453  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1454  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1456   The request requires user authentication (see &auth;).
1460<section title="402 Payment Required" anchor="status.402">
1461  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1462  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1464   This code is reserved for future use.
1468<section title="403 Forbidden" anchor="status.403">
1469  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1470  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1472   The server understood the request, but is refusing to fulfill it.
1473   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1474   If the request method was not HEAD and the server wishes to make
1475   public why the request has not been fulfilled, it &SHOULD; describe the
1476   reason for the refusal in the entity.  If the server does not wish to
1477   make this information available to the client, the status code 404
1478   (Not Found) can be used instead.
1482<section title="404 Not Found" anchor="status.404">
1483  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1484  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1486   The server has not found anything matching the Request-URI. No
1487   indication is given of whether the condition is temporary or
1488   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1489   knows, through some internally configurable mechanism, that an old
1490   resource is permanently unavailable and has no forwarding address.
1491   This status code is commonly used when the server does not wish to
1492   reveal exactly why the request has been refused, or when no other
1493   response is applicable.
1497<section title="405 Method Not Allowed" anchor="status.405">
1498  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1499  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1501   The method specified in the Request-Line is not allowed for the
1502   resource identified by the Request-URI. The response &MUST; include an
1503   Allow header containing a list of valid methods for the requested
1504   resource.
1508<section title="406 Not Acceptable" anchor="status.406">
1509  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1510  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1512   The resource identified by the request is only capable of generating
1513   response entities which have content characteristics not acceptable
1514   according to the accept headers sent in the request.
1517   Unless it was a HEAD request, the response &SHOULD; include an entity
1518   containing a list of available entity characteristics and location(s)
1519   from which the user or user agent can choose the one most
1520   appropriate. The entity format is specified by the media type given
1521   in the Content-Type header field. Depending upon the format and the
1522   capabilities of the user agent, selection of the most appropriate
1523   choice &MAY; be performed automatically. However, this specification
1524   does not define any standard for such automatic selection.
1525  <list><t>
1526      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1527      not acceptable according to the accept headers sent in the
1528      request. In some cases, this may even be preferable to sending a
1529      406 response. User agents are encouraged to inspect the headers of
1530      an incoming response to determine if it is acceptable.
1531  </t></list>
1534   If the response could be unacceptable, a user agent &SHOULD;
1535   temporarily stop receipt of more data and query the user for a
1536   decision on further actions.
1540<section title="407 Proxy Authentication Required" anchor="status.407">
1541  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1542  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1544   This code is similar to 401 (Unauthorized), but indicates that the
1545   client must first authenticate itself with the proxy (see &auth;).
1549<section title="408 Request Timeout" anchor="status.408">
1550  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1551  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1553   The client did not produce a request within the time that the server
1554   was prepared to wait. The client &MAY; repeat the request without
1555   modifications at any later time.
1559<section title="409 Conflict" anchor="status.409">
1560  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1561  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1563   The request could not be completed due to a conflict with the current
1564   state of the resource. This code is only allowed in situations where
1565   it is expected that the user might be able to resolve the conflict
1566   and resubmit the request. The response body &SHOULD; include enough
1567   information for the user to recognize the source of the conflict.
1568   Ideally, the response entity would include enough information for the
1569   user or user agent to fix the problem; however, that might not be
1570   possible and is not required.
1573   Conflicts are most likely to occur in response to a PUT request. For
1574   example, if versioning were being used and the entity being PUT
1575   included changes to a resource which conflict with those made by an
1576   earlier (third-party) request, the server might use the 409 response
1577   to indicate that it can't complete the request. In this case, the
1578   response entity would likely contain a list of the differences
1579   between the two versions in a format defined by the response
1580   Content-Type.
1584<section title="410 Gone" anchor="status.410">
1585  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1586  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1588   The requested resource is no longer available at the server and no
1589   forwarding address is known. This condition is expected to be
1590   considered permanent. Clients with link editing capabilities &SHOULD;
1591   delete references to the Request-URI after user approval. If the
1592   server does not know, or has no facility to determine, whether or not
1593   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1594   used instead. This response is cacheable unless indicated otherwise.
1597   The 410 response is primarily intended to assist the task of web
1598   maintenance by notifying the recipient that the resource is
1599   intentionally unavailable and that the server owners desire that
1600   remote links to that resource be removed. Such an event is common for
1601   limited-time, promotional services and for resources belonging to
1602   individuals no longer working at the server's site. It is not
1603   necessary to mark all permanently unavailable resources as "gone" or
1604   to keep the mark for any length of time -- that is left to the
1605   discretion of the server owner.
1609<section title="411 Length Required" anchor="status.411">
1610  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1611  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1613   The server refuses to accept the request without a defined Content-Length.
1614   The client &MAY; repeat the request if it adds a valid
1615   Content-Length header field containing the length of the message-body
1616   in the request message.
1620<section title="412 Precondition Failed" anchor="status.412">
1621  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1622  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1624   The precondition given in one or more of the request-header fields
1625   evaluated to false when it was tested on the server, as defined in
1626   &conditional;.
1630<section title="413 Request Entity Too Large" anchor="status.413">
1631  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1632  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1634   The server is refusing to process a request because the request
1635   entity is larger than the server is willing or able to process. The
1636   server &MAY; close the connection to prevent the client from continuing
1637   the request.
1640   If the condition is temporary, the server &SHOULD; include a Retry-After
1641   header field to indicate that it is temporary and after what
1642   time the client &MAY; try again.
1646<section title="414 Request-URI Too Long" anchor="status.414">
1647  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1648  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1650   The server is refusing to service the request because the Request-URI
1651   is longer than the server is willing to interpret. This rare
1652   condition is only likely to occur when a client has improperly
1653   converted a POST request to a GET request with long query
1654   information, when the client has descended into a URI "black hole" of
1655   redirection (e.g., a redirected URI prefix that points to a suffix of
1656   itself), or when the server is under attack by a client attempting to
1657   exploit security holes present in some servers using fixed-length
1658   buffers for reading or manipulating the Request-URI.
1662<section title="415 Unsupported Media Type" anchor="status.415">
1663  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1664  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1666   The server is refusing to service the request because the entity of
1667   the request is in a format not supported by the requested resource
1668   for the requested method.
1672<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1673  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1674  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1676   The request included a Range request-header field (&header-range;) and none of
1677   the range-specifier values in this field overlap the current extent
1678   of the selected resource.
1682<section title="417 Expectation Failed" anchor="status.417">
1683  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1684  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1686   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1687   could not be met by this server, or, if the server is a proxy,
1688   the server has unambiguous evidence that the request could not be met
1689   by the next-hop server.
1694<section title="Server Error 5xx" anchor="status.5xx">
1696   Response status codes beginning with the digit "5" indicate cases in
1697   which the server is aware that it has erred or is incapable of
1698   performing the request. Except when responding to a HEAD request, the
1699   server &SHOULD; include an entity containing an explanation of the
1700   error situation, and whether it is a temporary or permanent
1701   condition. User agents &SHOULD; display any included entity to the
1702   user. These response codes are applicable to any request method.
1705<section title="500 Internal Server Error" anchor="status.500">
1706  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1707  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1709   The server encountered an unexpected condition which prevented it
1710   from fulfilling the request.
1714<section title="501 Not Implemented" anchor="status.501">
1715  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1716  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1718   The server does not support the functionality required to fulfill the
1719   request. This is the appropriate response when the server does not
1720   recognize the request method and is not capable of supporting it for
1721   any resource.
1725<section title="502 Bad Gateway" anchor="status.502">
1726  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1727  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1729   The server, while acting as a gateway or proxy, received an invalid
1730   response from the upstream server it accessed in attempting to
1731   fulfill the request.
1735<section title="503 Service Unavailable" anchor="status.503">
1736  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1737  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1739   The server is currently unable to handle the request due to a
1740   temporary overloading or maintenance of the server. The implication
1741   is that this is a temporary condition which will be alleviated after
1742   some delay. If known, the length of the delay &MAY; be indicated in a
1743   Retry-After header. If no Retry-After is given, the client &SHOULD;
1744   handle the response as it would for a 500 response.
1745  <list><t>
1746      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1747      server must use it when becoming overloaded. Some servers may wish
1748      to simply refuse the connection.
1749  </t></list>
1753<section title="504 Gateway Timeout" anchor="status.504">
1754  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1755  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1757   The server, while acting as a gateway or proxy, did not receive a
1758   timely response from the upstream server specified by the URI (e.g.
1759   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1760   to access in attempting to complete the request.
1761  <list><t>
1762      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1763      return 400 or 500 when DNS lookups time out.
1764  </t></list>
1768<section title="505 HTTP Version Not Supported" anchor="status.505">
1769  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1770  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1772   The server does not support, or refuses to support, the protocol
1773   version that was used in the request message. The server is
1774   indicating that it is unable or unwilling to complete the request
1775   using the same major version as the client, as described in &http-version;,
1776   other than with this error message. The response &SHOULD; contain
1777   an entity describing why that version is not supported and what other
1778   protocols are supported by that server.
1786<section title="Header Field Definitions" anchor="header.fields">
1788   This section defines the syntax and semantics of HTTP/1.1 header fields
1789   related to request and response semantics.
1792   For entity-header fields, both sender and recipient refer to either the
1793   client or the server, depending on who sends and who receives the entity.
1796<section title="Allow" anchor="header.allow">
1797  <iref primary="true" item="Allow header" x:for-anchor=""/>
1798  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1799  <x:anchor-alias value="Allow"/>
1800  <x:anchor-alias value="Allow-v"/>
1802      The response-header field "Allow" lists the set of methods advertised as
1803      supported by the resource identified by the Request-URI. The purpose of
1804      this field is strictly to inform the recipient of valid methods
1805      associated with the resource. An Allow header field &MUST; be
1806      present in a 405 (Method Not Allowed) response.
1808<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1809  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1810  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1813      Example of use:
1815<figure><artwork type="example">
1816  Allow: GET, HEAD, PUT
1819      The actual set of allowed methods is defined
1820      by the origin server at the time of each request.
1823      A proxy &MUST-NOT; modify the Allow header field even if it does not
1824      understand all the methods specified, since the user agent might
1825      have other means of communicating with the origin server.
1829<section title="Expect" anchor="header.expect">
1830  <iref primary="true" item="Expect header" x:for-anchor=""/>
1831  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1832  <x:anchor-alias value="Expect"/>
1833  <x:anchor-alias value="Expect-v"/>
1834  <x:anchor-alias value="expectation"/>
1835  <x:anchor-alias value="expectation-extension"/>
1836  <x:anchor-alias value="expect-params"/>
1838   The request-header field "Expect" is used to indicate that particular
1839   server behaviors are required by the client.
1841<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1842  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1843  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1845  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1846  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1847                           *<x:ref>expect-params</x:ref> ]
1848  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1851   A server that does not understand or is unable to comply with any of
1852   the expectation values in the Expect field of a request &MUST; respond
1853   with appropriate error status. The server &MUST; respond with a 417
1854   (Expectation Failed) status if any of the expectations cannot be met
1855   or, if there are other problems with the request, some other 4xx
1856   status.
1859   This header field is defined with extensible syntax to allow for
1860   future extensions. If a server receives a request containing an
1861   Expect field that includes an expectation-extension that it does not
1862   support, it &MUST; respond with a 417 (Expectation Failed) status.
1865   Comparison of expectation values is case-insensitive for unquoted
1866   tokens (including the 100-continue token), and is case-sensitive for
1867   quoted-string expectation-extensions.
1870   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1871   return a 417 (Expectation Failed) status if it receives a request
1872   with an expectation that it cannot meet. However, the Expect
1873   request-header itself is end-to-end; it &MUST; be forwarded if the
1874   request is forwarded.
1877   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1878   Expect header.
1881   See &use100; for the use of the 100 (Continue) status.
1885<section title="From" anchor="header.from">
1886  <iref primary="true" item="From header" x:for-anchor=""/>
1887  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1888  <x:anchor-alias value="From"/>
1889  <x:anchor-alias value="From-v"/>
1890  <x:anchor-alias value="mailbox"/>
1892   The request-header field "From", if given, &SHOULD; contain an Internet
1893   e-mail address for the human user who controls the requesting user
1894   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1895   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1897<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1898  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1899  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1901  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1904   An example is:
1906<figure><artwork type="example">
1907  From:
1910   This header field &MAY; be used for logging purposes and as a means for
1911   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1912   be used as an insecure form of access protection. The interpretation
1913   of this field is that the request is being performed on behalf of the
1914   person given, who accepts responsibility for the method performed. In
1915   particular, robot agents &SHOULD; include this header so that the
1916   person responsible for running the robot can be contacted if problems
1917   occur on the receiving end.
1920   The Internet e-mail address in this field &MAY; be separate from the
1921   Internet host which issued the request. For example, when a request
1922   is passed through a proxy the original issuer's address &SHOULD; be
1923   used.
1926   The client &SHOULD-NOT;  send the From header field without the user's
1927   approval, as it might conflict with the user's privacy interests or
1928   their site's security policy. It is strongly recommended that the
1929   user be able to disable, enable, and modify the value of this field
1930   at any time prior to a request.
1934<section title="Location" anchor="header.location">
1935  <iref primary="true" item="Location header" x:for-anchor=""/>
1936  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1937  <x:anchor-alias value="Location"/>
1938  <x:anchor-alias value="Location-v"/>
1940   The response-header field "Location" is used for the identification of a
1941   new resource or to redirect the recipient to a location other than the
1942   Request-URI for completion of the request.  For 201 (Created)
1943   responses, the Location is that of the new resource which was created
1944   by the request. For 3xx responses, the location &SHOULD; indicate the
1945   server's preferred URI for automatic redirection to the resource. The
1946   field value consists of a single absolute URI.
1948<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1949  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1950  <x:ref>Location-v</x:ref>     = <x:ref>absoluteURI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1953   An example is:
1955<figure><artwork type="example">
1956  Location:
1959  <list><t>
1960      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1961      from Location in that the Content-Location identifies the original
1962      location of the entity enclosed in the response. It is therefore
1963      possible for a response to contain header fields for both Location
1964      and Content-Location.
1965  </t></list>
1968   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1969   <list style="symbols">
1970      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1971      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1972      <t>With 305 Use Proxy.</t>
1973   </list>
1977<section title="Max-Forwards" anchor="header.max-forwards">
1978  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1979  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1980  <x:anchor-alias value="Max-Forwards"/>
1981  <x:anchor-alias value="Max-Forwards-v"/>
1983   The request-header "Max-Forwards" field provides a mechanism with the
1984   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1985   number of proxies or gateways that can forward the request to the
1986   next inbound server. This can be useful when the client is attempting
1987   to trace a request chain which appears to be failing or looping in
1988   mid-chain.
1990<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
1991  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
1992  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
1995   The Max-Forwards value is a decimal integer indicating the remaining
1996   number of times this request message may be forwarded.
1999   Each proxy or gateway recipient of a TRACE or OPTIONS request
2000   containing a Max-Forwards header field &MUST; check and update its
2001   value prior to forwarding the request. If the received value is zero
2002   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2003   respond as the final recipient. If the received Max-Forwards value is
2004   greater than zero, then the forwarded message &MUST; contain an updated
2005   Max-Forwards field with a value decremented by one (1).
2008   The Max-Forwards header field &MAY; be ignored for all other methods
2009   defined by this specification and for any extension methods for which
2010   it is not explicitly referred to as part of that method definition.
2014<section title="Referer" anchor="header.referer">
2015  <iref primary="true" item="Referer header" x:for-anchor=""/>
2016  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2017  <x:anchor-alias value="Referer"/>
2018  <x:anchor-alias value="Referer-v"/>
2020   The request-header field "Referer" [sic] allows the client to specify,
2021   for the server's benefit, the address (URI) of the resource from
2022   which the Request-URI was obtained (the "referrer", although the
2023   header field is misspelled.) The Referer request-header allows a
2024   server to generate lists of back-links to resources for interest,
2025   logging, optimized caching, etc. It also allows obsolete or mistyped
2026   links to be traced for maintenance. The Referer field &MUST-NOT; be
2027   sent if the Request-URI was obtained from a source that does not have
2028   its own URI, such as input from the user keyboard.
2030<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2031  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2032  <x:ref>Referer-v</x:ref>      = <x:ref>absoluteURI</x:ref> / <x:ref>relativeURI</x:ref>
2035   Example:
2037<figure><artwork type="example">
2038  Referer:
2041   If the field value is a relative URI, it &SHOULD; be interpreted
2042   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2043   <xref target=""/> for security considerations.
2047<section title="Retry-After" anchor="header.retry-after">
2048  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2049  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2050  <x:anchor-alias value="Retry-After"/>
2051  <x:anchor-alias value="Retry-After-v"/>
2053   The response-header "Retry-After" field can be used with a 503 (Service
2054   Unavailable) response to indicate how long the service is expected to
2055   be unavailable to the requesting client. This field &MAY; also be used
2056   with any 3xx (Redirection) response to indicate the minimum time the
2057   user-agent is asked wait before issuing the redirected request. The
2058   value of this field can be either an HTTP-date or an integer number
2059   of seconds (in decimal) after the time of the response.
2061<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2062  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2063  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2065<t anchor="">
2066  <x:anchor-alias value="delta-seconds"/>
2067   Time spans are non-negative decimal integers, representing time in
2068   seconds.
2070<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2071  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2074   Two examples of its use are
2076<figure><artwork type="example">
2077  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2078  Retry-After: 120
2081   In the latter example, the delay is 2 minutes.
2085<section title="Server" anchor="header.server">
2086  <iref primary="true" item="Server header" x:for-anchor=""/>
2087  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2088  <x:anchor-alias value="Server"/>
2089  <x:anchor-alias value="Server-v"/>
2091   The response-header field "Server" contains information about the
2092   software used by the origin server to handle the request. The field
2093   can contain multiple product tokens (&product-tokens;) and comments
2094   identifying the server and any significant subproducts. The product
2095   tokens are listed in order of their significance for identifying the
2096   application.
2098<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2099  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2100  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2101                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2104   Example:
2106<figure><artwork type="example">
2107  Server: CERN/3.0 libwww/2.17
2110   If the response is being forwarded through a proxy, the proxy
2111   application &MUST-NOT; modify the Server response-header. Instead, it
2112   &MUST; include a Via field (as described in &header-via;).
2113  <list><t>
2114      <x:h>Note:</x:h> Revealing the specific software version of the server might
2115      allow the server machine to become more vulnerable to attacks
2116      against software that is known to contain security holes. Server
2117      implementors are encouraged to make this field a configurable
2118      option.
2119  </t></list>
2123<section title="User-Agent" anchor="header.user-agent">
2124  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2125  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2126  <x:anchor-alias value="User-Agent"/>
2127  <x:anchor-alias value="User-Agent-v"/>
2129   The request-header field "User-Agent" contains information about the
2130   user agent originating the request. This is for statistical purposes,
2131   the tracing of protocol violations, and automated recognition of user
2132   agents for the sake of tailoring responses to avoid particular user
2133   agent limitations. User agents &SHOULD; include this field with
2134   requests. The field can contain multiple product tokens (&product-tokens;)
2135   and comments identifying the agent and any subproducts which form a
2136   significant part of the user agent. By convention, the product tokens
2137   are listed in order of their significance for identifying the
2138   application.
2140<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2141  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2142  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2143                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2146   Example:
2148<figure><artwork type="example">
2149  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2155<section title="IANA Considerations" anchor="IANA.considerations">
2157<section title="Method Registry" anchor="method.registration">
2159  The registration procedure for HTTP Methods is defined by
2160  <xref target="method.registry"/> of this document.
2163   The HTTP Method Registry located at <eref target=""/>
2164   should be populated with the registrations below:
2166<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2167<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2168   <ttcol>Method</ttcol>
2169   <ttcol>Safe</ttcol>
2170   <ttcol>Reference</ttcol>
2171   <c>CONNECT</c>
2172   <c>no</c>
2173   <c>
2174      <xref target="CONNECT"/>
2175   </c>
2176   <c>DELETE</c>
2177   <c>no</c>
2178   <c>
2179      <xref target="DELETE"/>
2180   </c>
2181   <c>GET</c>
2182   <c>yes</c>
2183   <c>
2184      <xref target="GET"/>
2185   </c>
2186   <c>HEAD</c>
2187   <c>yes</c>
2188   <c>
2189      <xref target="HEAD"/>
2190   </c>
2191   <c>OPTIONS</c>
2192   <c>yes</c>
2193   <c>
2194      <xref target="OPTIONS"/>
2195   </c>
2196   <c>POST</c>
2197   <c>no</c>
2198   <c>
2199      <xref target="POST"/>
2200   </c>
2201   <c>PUT</c>
2202   <c>no</c>
2203   <c>
2204      <xref target="PUT"/>
2205   </c>
2206   <c>TRACE</c>
2207   <c>yes</c>
2208   <c>
2209      <xref target="TRACE"/>
2210   </c>
2215<section title="Status Code Registry" anchor="status.code.registration">
2217   The registration procedure for HTTP Status Codes -- previously defined
2218   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2219   by <xref target="status.code.registry"/> of this document.
2222   The HTTP Status Code Registry located at <eref target=""/>
2223   should be updated with the registrations below:
2225<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2226<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2227   <ttcol>Value</ttcol>
2228   <ttcol>Description</ttcol>
2229   <ttcol>Reference</ttcol>
2230   <c>100</c>
2231   <c>Continue</c>
2232   <c>
2233      <xref target="status.100"/>
2234   </c>
2235   <c>101</c>
2236   <c>Switching Protocols</c>
2237   <c>
2238      <xref target="status.101"/>
2239   </c>
2240   <c>200</c>
2241   <c>OK</c>
2242   <c>
2243      <xref target="status.200"/>
2244   </c>
2245   <c>201</c>
2246   <c>Created</c>
2247   <c>
2248      <xref target="status.201"/>
2249   </c>
2250   <c>202</c>
2251   <c>Accepted</c>
2252   <c>
2253      <xref target="status.202"/>
2254   </c>
2255   <c>203</c>
2256   <c>Non-Authoritative Information</c>
2257   <c>
2258      <xref target="status.203"/>
2259   </c>
2260   <c>204</c>
2261   <c>No Content</c>
2262   <c>
2263      <xref target="status.204"/>
2264   </c>
2265   <c>205</c>
2266   <c>Reset Content</c>
2267   <c>
2268      <xref target="status.205"/>
2269   </c>
2270   <c>206</c>
2271   <c>Partial Content</c>
2272   <c>
2273      <xref target="status.206"/>
2274   </c>
2275   <c>300</c>
2276   <c>Multiple Choices</c>
2277   <c>
2278      <xref target="status.300"/>
2279   </c>
2280   <c>301</c>
2281   <c>Moved Permanently</c>
2282   <c>
2283      <xref target="status.301"/>
2284   </c>
2285   <c>302</c>
2286   <c>Found</c>
2287   <c>
2288      <xref target="status.302"/>
2289   </c>
2290   <c>303</c>
2291   <c>See Other</c>
2292   <c>
2293      <xref target="status.303"/>
2294   </c>
2295   <c>304</c>
2296   <c>Not Modified</c>
2297   <c>
2298      <xref target="status.304"/>
2299   </c>
2300   <c>305</c>
2301   <c>Use Proxy</c>
2302   <c>
2303      <xref target="status.305"/>
2304   </c>
2305   <c>306</c>
2306   <c>(Unused)</c>
2307   <c>
2308      <xref target="status.306"/>
2309   </c>
2310   <c>307</c>
2311   <c>Temporary Redirect</c>
2312   <c>
2313      <xref target="status.307"/>
2314   </c>
2315   <c>400</c>
2316   <c>Bad Request</c>
2317   <c>
2318      <xref target="status.400"/>
2319   </c>
2320   <c>401</c>
2321   <c>Unauthorized</c>
2322   <c>
2323      <xref target="status.401"/>
2324   </c>
2325   <c>402</c>
2326   <c>Payment Required</c>
2327   <c>
2328      <xref target="status.402"/>
2329   </c>
2330   <c>403</c>
2331   <c>Forbidden</c>
2332   <c>
2333      <xref target="status.403"/>
2334   </c>
2335   <c>404</c>
2336   <c>Not Found</c>
2337   <c>
2338      <xref target="status.404"/>
2339   </c>
2340   <c>405</c>
2341   <c>Method Not Allowed</c>
2342   <c>
2343      <xref target="status.405"/>
2344   </c>
2345   <c>406</c>
2346   <c>Not Acceptable</c>
2347   <c>
2348      <xref target="status.406"/>
2349   </c>
2350   <c>407</c>
2351   <c>Proxy Authentication Required</c>
2352   <c>
2353      <xref target="status.407"/>
2354   </c>
2355   <c>408</c>
2356   <c>Request Timeout</c>
2357   <c>
2358      <xref target="status.408"/>
2359   </c>
2360   <c>409</c>
2361   <c>Conflict</c>
2362   <c>
2363      <xref target="status.409"/>
2364   </c>
2365   <c>410</c>
2366   <c>Gone</c>
2367   <c>
2368      <xref target="status.410"/>
2369   </c>
2370   <c>411</c>
2371   <c>Length Required</c>
2372   <c>
2373      <xref target="status.411"/>
2374   </c>
2375   <c>412</c>
2376   <c>Precondition Failed</c>
2377   <c>
2378      <xref target="status.412"/>
2379   </c>
2380   <c>413</c>
2381   <c>Request Entity Too Large</c>
2382   <c>
2383      <xref target="status.413"/>
2384   </c>
2385   <c>414</c>
2386   <c>Request-URI Too Long</c>
2387   <c>
2388      <xref target="status.414"/>
2389   </c>
2390   <c>415</c>
2391   <c>Unsupported Media Type</c>
2392   <c>
2393      <xref target="status.415"/>
2394   </c>
2395   <c>416</c>
2396   <c>Requested Range Not Satisfiable</c>
2397   <c>
2398      <xref target="status.416"/>
2399   </c>
2400   <c>417</c>
2401   <c>Expectation Failed</c>
2402   <c>
2403      <xref target="status.417"/>
2404   </c>
2405   <c>500</c>
2406   <c>Internal Server Error</c>
2407   <c>
2408      <xref target="status.500"/>
2409   </c>
2410   <c>501</c>
2411   <c>Not Implemented</c>
2412   <c>
2413      <xref target="status.501"/>
2414   </c>
2415   <c>502</c>
2416   <c>Bad Gateway</c>
2417   <c>
2418      <xref target="status.502"/>
2419   </c>
2420   <c>503</c>
2421   <c>Service Unavailable</c>
2422   <c>
2423      <xref target="status.503"/>
2424   </c>
2425   <c>504</c>
2426   <c>Gateway Timeout</c>
2427   <c>
2428      <xref target="status.504"/>
2429   </c>
2430   <c>505</c>
2431   <c>HTTP Version Not Supported</c>
2432   <c>
2433      <xref target="status.505"/>
2434   </c>
2438<section title="Message Header Registration" anchor="message.header.registration">
2440   The Message Header Registry located at <eref target=""/> should be updated
2441   with the permanent registrations below (see <xref target="RFC3864"/>):
2443<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2444<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2445   <ttcol>Header Field Name</ttcol>
2446   <ttcol>Protocol</ttcol>
2447   <ttcol>Status</ttcol>
2448   <ttcol>Reference</ttcol>
2449   <c>Allow</c>
2450   <c>http</c>
2451   <c>standard</c>
2452   <c>
2453      <xref target="header.allow"/>
2454   </c>
2455   <c>Expect</c>
2456   <c>http</c>
2457   <c>standard</c>
2458   <c>
2459      <xref target="header.expect"/>
2460   </c>
2461   <c>From</c>
2462   <c>http</c>
2463   <c>standard</c>
2464   <c>
2465      <xref target="header.from"/>
2466   </c>
2467   <c>Location</c>
2468   <c>http</c>
2469   <c>standard</c>
2470   <c>
2471      <xref target="header.location"/>
2472   </c>
2473   <c>Max-Forwards</c>
2474   <c>http</c>
2475   <c>standard</c>
2476   <c>
2477      <xref target="header.max-forwards"/>
2478   </c>
2479   <c>Referer</c>
2480   <c>http</c>
2481   <c>standard</c>
2482   <c>
2483      <xref target="header.referer"/>
2484   </c>
2485   <c>Retry-After</c>
2486   <c>http</c>
2487   <c>standard</c>
2488   <c>
2489      <xref target="header.retry-after"/>
2490   </c>
2491   <c>Server</c>
2492   <c>http</c>
2493   <c>standard</c>
2494   <c>
2495      <xref target="header.server"/>
2496   </c>
2497   <c>User-Agent</c>
2498   <c>http</c>
2499   <c>standard</c>
2500   <c>
2501      <xref target="header.user-agent"/>
2502   </c>
2506   The change controller is: "IETF ( - Internet Engineering Task Force".
2511<section title="Security Considerations" anchor="security.considerations">
2513   This section is meant to inform application developers, information
2514   providers, and users of the security limitations in HTTP/1.1 as
2515   described by this document. The discussion does not include
2516   definitive solutions to the problems revealed, though it does make
2517   some suggestions for reducing security risks.
2520<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2522   Like any generic data transfer protocol, HTTP cannot regulate the
2523   content of the data that is transferred, nor is there any a priori
2524   method of determining the sensitivity of any particular piece of
2525   information within the context of any given request. Therefore,
2526   applications &SHOULD; supply as much control over this information as
2527   possible to the provider of that information. Four header fields are
2528   worth special mention in this context: Server, Via, Referer and From.
2531   Revealing the specific software version of the server might allow the
2532   server machine to become more vulnerable to attacks against software
2533   that is known to contain security holes. Implementors &SHOULD; make the
2534   Server header field a configurable option.
2537   Proxies which serve as a portal through a network firewall &SHOULD;
2538   take special precautions regarding the transfer of header information
2539   that identifies the hosts behind the firewall. In particular, they
2540   &SHOULD; remove, or replace with sanitized versions, any Via fields
2541   generated behind the firewall.
2544   The Referer header allows reading patterns to be studied and reverse
2545   links drawn. Although it can be very useful, its power can be abused
2546   if user details are not separated from the information contained in
2547   the Referer. Even when the personal information has been removed, the
2548   Referer header might indicate a private document's URI whose
2549   publication would be inappropriate.
2552   The information sent in the From field might conflict with the user's
2553   privacy interests or their site's security policy, and hence it
2554   &SHOULD-NOT;  be transmitted without the user being able to disable,
2555   enable, and modify the contents of the field. The user &MUST; be able
2556   to set the contents of this field within a user preference or
2557   application defaults configuration.
2560   We suggest, though do not require, that a convenient toggle interface
2561   be provided for the user to enable or disable the sending of From and
2562   Referer information.
2565   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2566   fields can sometimes be used to determine that a specific client or
2567   server have a particular security hole which might be exploited.
2568   Unfortunately, this same information is often used for other valuable
2569   purposes for which HTTP currently has no better mechanism.
2573<section title="Encoding Sensitive Information in URIs" anchor="">
2575   Because the source of a link might be private information or might
2576   reveal an otherwise private information source, it is strongly
2577   recommended that the user be able to select whether or not the
2578   Referer field is sent. For example, a browser client could have a
2579   toggle switch for browsing openly/anonymously, which would
2580   respectively enable/disable the sending of Referer and From
2581   information.
2584   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2585   HTTP request if the referring page was transferred with a secure
2586   protocol.
2589   Authors of services should not use
2590   GET-based forms for the submission of sensitive data because that
2591   data will be encoded in the Request-URI. Many existing
2592   servers, proxies, and user agents log or display the Request-URI in
2593   places where it might be visible to third parties. Such services can
2594   use POST-based form submission instead.
2598<section title="Location Headers and Spoofing" anchor="location.spoofing">
2600   If a single server supports multiple organizations that do not trust
2601   one another, then it &MUST; check the values of Location and Content-Location
2602   headers in responses that are generated under control of
2603   said organizations to make sure that they do not attempt to
2604   invalidate resources over which they have no authority.
2610<section title="Acknowledgments" anchor="ack">
2615<references title="Normative References">
2617<reference anchor="Part1">
2618  <front>
2619    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2620    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2621      <organization abbrev="Day Software">Day Software</organization>
2622      <address><email></email></address>
2623    </author>
2624    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2625      <organization>One Laptop per Child</organization>
2626      <address><email></email></address>
2627    </author>
2628    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2629      <organization abbrev="HP">Hewlett-Packard Company</organization>
2630      <address><email></email></address>
2631    </author>
2632    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2633      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2634      <address><email></email></address>
2635    </author>
2636    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2637      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2638      <address><email></email></address>
2639    </author>
2640    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2641      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2642      <address><email></email></address>
2643    </author>
2644    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2645      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2646      <address><email></email></address>
2647    </author>
2648    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2649      <organization abbrev="W3C">World Wide Web Consortium</organization>
2650      <address><email></email></address>
2651    </author>
2652    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2653      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2654      <address><email></email></address>
2655    </author>
2656    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2657  </front>
2658  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2659  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2662<reference anchor="Part3">
2663  <front>
2664    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2665    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2666      <organization abbrev="Day Software">Day Software</organization>
2667      <address><email></email></address>
2668    </author>
2669    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2670      <organization>One Laptop per Child</organization>
2671      <address><email></email></address>
2672    </author>
2673    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2674      <organization abbrev="HP">Hewlett-Packard Company</organization>
2675      <address><email></email></address>
2676    </author>
2677    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2678      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2679      <address><email></email></address>
2680    </author>
2681    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2682      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2683      <address><email></email></address>
2684    </author>
2685    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2686      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2687      <address><email></email></address>
2688    </author>
2689    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2690      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2691      <address><email></email></address>
2692    </author>
2693    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2694      <organization abbrev="W3C">World Wide Web Consortium</organization>
2695      <address><email></email></address>
2696    </author>
2697    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2698      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2699      <address><email></email></address>
2700    </author>
2701    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2702  </front>
2703  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2704  <x:source href="p3-payload.xml" basename="p3-payload"/>
2707<reference anchor="Part4">
2708  <front>
2709    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2710    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2711      <organization abbrev="Day Software">Day Software</organization>
2712      <address><email></email></address>
2713    </author>
2714    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2715      <organization>One Laptop per Child</organization>
2716      <address><email></email></address>
2717    </author>
2718    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2719      <organization abbrev="HP">Hewlett-Packard Company</organization>
2720      <address><email></email></address>
2721    </author>
2722    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2723      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2724      <address><email></email></address>
2725    </author>
2726    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2727      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2728      <address><email></email></address>
2729    </author>
2730    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2731      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2732      <address><email></email></address>
2733    </author>
2734    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2735      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2736      <address><email></email></address>
2737    </author>
2738    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2739      <organization abbrev="W3C">World Wide Web Consortium</organization>
2740      <address><email></email></address>
2741    </author>
2742    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2743      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2744      <address><email></email></address>
2745    </author>
2746    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2747  </front>
2748  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2749  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2752<reference anchor="Part5">
2753  <front>
2754    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2755    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2756      <organization abbrev="Day Software">Day Software</organization>
2757      <address><email></email></address>
2758    </author>
2759    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2760      <organization>One Laptop per Child</organization>
2761      <address><email></email></address>
2762    </author>
2763    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2764      <organization abbrev="HP">Hewlett-Packard Company</organization>
2765      <address><email></email></address>
2766    </author>
2767    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2768      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2769      <address><email></email></address>
2770    </author>
2771    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2772      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2773      <address><email></email></address>
2774    </author>
2775    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2776      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2777      <address><email></email></address>
2778    </author>
2779    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2780      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2781      <address><email></email></address>
2782    </author>
2783    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2784      <organization abbrev="W3C">World Wide Web Consortium</organization>
2785      <address><email></email></address>
2786    </author>
2787    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2788      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2789      <address><email></email></address>
2790    </author>
2791    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2792  </front>
2793  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2794  <x:source href="p5-range.xml" basename="p5-range"/>
2797<reference anchor="Part6">
2798  <front>
2799    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2800    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2801      <organization abbrev="Day Software">Day Software</organization>
2802      <address><email></email></address>
2803    </author>
2804    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2805      <organization>One Laptop per Child</organization>
2806      <address><email></email></address>
2807    </author>
2808    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2809      <organization abbrev="HP">Hewlett-Packard Company</organization>
2810      <address><email></email></address>
2811    </author>
2812    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2813      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2814      <address><email></email></address>
2815    </author>
2816    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2817      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2818      <address><email></email></address>
2819    </author>
2820    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2821      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2822      <address><email></email></address>
2823    </author>
2824    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2825      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2826      <address><email></email></address>
2827    </author>
2828    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2829      <organization abbrev="W3C">World Wide Web Consortium</organization>
2830      <address><email></email></address>
2831    </author>
2832    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2833      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2834      <address><email></email></address>
2835    </author>
2836    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2837  </front>
2838  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2839  <x:source href="p6-cache.xml" basename="p6-cache"/>
2842<reference anchor="Part7">
2843  <front>
2844    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2845    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2846      <organization abbrev="Day Software">Day Software</organization>
2847      <address><email></email></address>
2848    </author>
2849    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2850      <organization>One Laptop per Child</organization>
2851      <address><email></email></address>
2852    </author>
2853    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2854      <organization abbrev="HP">Hewlett-Packard Company</organization>
2855      <address><email></email></address>
2856    </author>
2857    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2858      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2859      <address><email></email></address>
2860    </author>
2861    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2862      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2863      <address><email></email></address>
2864    </author>
2865    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2866      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2867      <address><email></email></address>
2868    </author>
2869    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2870      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2871      <address><email></email></address>
2872    </author>
2873    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2874      <organization abbrev="W3C">World Wide Web Consortium</organization>
2875      <address><email></email></address>
2876    </author>
2877    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2878      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2879      <address><email></email></address>
2880    </author>
2881    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2882  </front>
2883  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2884  <x:source href="p7-auth.xml" basename="p7-auth"/>
2887<reference anchor="RFC2119">
2888  <front>
2889    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2890    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2891      <organization>Harvard University</organization>
2892      <address><email></email></address>
2893    </author>
2894    <date month="March" year="1997"/>
2895  </front>
2896  <seriesInfo name="BCP" value="14"/>
2897  <seriesInfo name="RFC" value="2119"/>
2902<references title="Informative References">
2904<reference anchor="RFC1945">
2905  <front>
2906    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2907    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2908      <organization>MIT, Laboratory for Computer Science</organization>
2909      <address><email></email></address>
2910    </author>
2911    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2912      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2913      <address><email></email></address>
2914    </author>
2915    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2916      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2917      <address><email></email></address>
2918    </author>
2919    <date month="May" year="1996"/>
2920  </front>
2921  <seriesInfo name="RFC" value="1945"/>
2924<reference anchor="RFC2068">
2925  <front>
2926    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2927    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2928      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2929      <address><email></email></address>
2930    </author>
2931    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2932      <organization>MIT Laboratory for Computer Science</organization>
2933      <address><email></email></address>
2934    </author>
2935    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2936      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2937      <address><email></email></address>
2938    </author>
2939    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2940      <organization>MIT Laboratory for Computer Science</organization>
2941      <address><email></email></address>
2942    </author>
2943    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2944      <organization>MIT Laboratory for Computer Science</organization>
2945      <address><email></email></address>
2946    </author>
2947    <date month="January" year="1997"/>
2948  </front>
2949  <seriesInfo name="RFC" value="2068"/>
2952<reference anchor="RFC2616">
2953  <front>
2954    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2955    <author initials="R." surname="Fielding" fullname="R. Fielding">
2956      <organization>University of California, Irvine</organization>
2957      <address><email></email></address>
2958    </author>
2959    <author initials="J." surname="Gettys" fullname="J. Gettys">
2960      <organization>W3C</organization>
2961      <address><email></email></address>
2962    </author>
2963    <author initials="J." surname="Mogul" fullname="J. Mogul">
2964      <organization>Compaq Computer Corporation</organization>
2965      <address><email></email></address>
2966    </author>
2967    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2968      <organization>MIT Laboratory for Computer Science</organization>
2969      <address><email></email></address>
2970    </author>
2971    <author initials="L." surname="Masinter" fullname="L. Masinter">
2972      <organization>Xerox Corporation</organization>
2973      <address><email></email></address>
2974    </author>
2975    <author initials="P." surname="Leach" fullname="P. Leach">
2976      <organization>Microsoft Corporation</organization>
2977      <address><email></email></address>
2978    </author>
2979    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2980      <organization>W3C</organization>
2981      <address><email></email></address>
2982    </author>
2983    <date month="June" year="1999"/>
2984  </front>
2985  <seriesInfo name="RFC" value="2616"/>
2988<reference anchor='RFC2817'>
2989  <front>
2990    <title>Upgrading to TLS Within HTTP/1.1</title>
2991    <author initials='R.' surname='Khare' fullname='R. Khare'>
2992      <organization>4K Associates / UC Irvine</organization>
2993      <address><email></email></address>
2994    </author>
2995    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2996      <organization>Agranat Systems, Inc.</organization>
2997      <address><email></email></address>
2998    </author>
2999    <date year='2000' month='May' />
3000  </front>
3001  <seriesInfo name='RFC' value='2817' />
3004<reference anchor='RFC3864'>
3005  <front>
3006    <title>Registration Procedures for Message Header Fields</title>
3007    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3008      <organization>Nine by Nine</organization>
3009      <address><email></email></address>
3010    </author>
3011    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3012      <organization>BEA Systems</organization>
3013      <address><email></email></address>
3014    </author>
3015    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3016      <organization>HP Labs</organization>
3017      <address><email></email></address>
3018    </author>
3019    <date year='2004' month='September' />
3020  </front>
3021  <seriesInfo name='BCP' value='90' />
3022  <seriesInfo name='RFC' value='3864' />
3025<reference anchor='RFC5226'>
3026  <front>
3027    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3028    <author initials='T.' surname='Narten' fullname='T. Narten'>
3029      <organization>IBM</organization>
3030      <address><email></email></address>
3031    </author>
3032    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3033      <organization>Google</organization>
3034      <address><email></email></address>
3035    </author>
3036    <date year='2008' month='May' />
3037  </front>
3038  <seriesInfo name='BCP' value='26' />
3039  <seriesInfo name='RFC' value='5226' />
3042<reference anchor="RFC5322">
3043  <front>
3044    <title>Internet Message Format</title>
3045    <author initials="P." surname="Resnick" fullname="P. Resnick">
3046      <organization>Qualcomm Incorporated</organization>
3047    </author>
3048    <date year="2008" month="October"/>
3049  </front>
3050  <seriesInfo name="RFC" value="5322"/>
3055<section title="Compatibility with Previous Versions" anchor="compatibility">
3056<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3058   Clarified which error code should be used for inbound server failures
3059   (e.g. DNS failures). (<xref target="status.504"/>).
3062   201 (Created) had a race that required an Etag be sent when a resource is
3063   first created. (<xref target="status.201"/>).
3066   Rewrite of message transmission requirements to make it much harder
3067   for implementors to get it wrong, as the consequences of errors here
3068   can have significant impact on the Internet, and to deal with the
3069   following problems:
3070  <list style="numbers">
3071      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3072         this was incorrectly placing a requirement on the behavior of
3073         an implementation of a future version of HTTP/1.x</t>
3075      <t>Made it clear that user-agents should retry requests, not
3076         "clients" in general.</t>
3078      <t>Converted requirements for clients to ignore unexpected 100
3079         (Continue) responses, and for proxies to forward 100 responses,
3080         into a general requirement for 1xx responses.</t>
3082      <t>Modified some TCP-specific language, to make it clearer that
3083         non-TCP transports are possible for HTTP.</t>
3085      <t>Require that the origin server &MUST-NOT; wait for the request
3086         body before it sends a required 100 (Continue) response.</t>
3088      <t>Allow, rather than require, a server to omit 100 (Continue) if
3089         it has already seen some of the request body.</t>
3091      <t>Allow servers to defend against denial-of-service attacks and
3092         broken clients.</t>
3093  </list>
3096   This change adds the Expect header and 417 status code.
3099   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3100   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3103   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
3104   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3108<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3110  This document takes over the Status Code Registry, previously defined
3111  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3112  (<xref target="status.code.registry"/>)
3115  Clarify definition of POST.
3116  (<xref target="POST"/>)
3119  Failed to consider that there are
3120  many other request methods that are safe to automatically redirect,
3121  and further that the user agent is able to make that determination
3122  based on the request method semantics.
3123  (Sections <xref format="counter" target="status.301"/>,
3124  <xref format="counter" target="status.302"/> and
3125  <xref format="counter" target="status.307"/>)
3128  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3129  It used to indicate that the requested resource must be accessed through the
3130  proxy given by the Location field. The Location field gave the URI of the
3131  proxy. The recipient was expected to repeat this single request via the proxy.
3132  (<xref target="status.305"/>)
3135  Reclassify Allow header as response header, removing the option to
3136  specify it in a PUT request.
3137  Relax the server requirement on the contents of the Allow header and
3138  remove requirement on clients to always trust the header value.
3139  (<xref target="header.allow"/>)
3142  Correct syntax of Location header to allow fragment,
3143  as referred symbol wasn't what was expected, and add some
3144  clarifications as to when it would not be appropriate.
3145  (<xref target="header.location"/>)
3148  In the description of the Server header, the Via field
3149  was described as a SHOULD. The requirement was and is stated
3150  correctly in the description of the Via header in &header-via;.
3151  (<xref target="header.server"/>)
3157<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3159<section title="Since RFC2616">
3161  Extracted relevant partitions from <xref target="RFC2616"/>.
3165<section title="Since draft-ietf-httpbis-p2-semantics-00">
3167  Closed issues:
3168  <list style="symbols">
3169    <t>
3170      <eref target=""/>:
3171      "Via is a MUST"
3172      (<eref target=""/>)
3173    </t>
3174    <t>
3175      <eref target=""/>:
3176      "Fragments allowed in Location"
3177      (<eref target=""/>)
3178    </t>
3179    <t>
3180      <eref target=""/>:
3181      "Safe Methods vs Redirection"
3182      (<eref target=""/>)
3183    </t>
3184    <t>
3185      <eref target=""/>:
3186      "Revise description of the POST method"
3187      (<eref target=""/>)
3188    </t>
3189    <t>
3190      <eref target=""/>:
3191      "Normative and Informative references"
3192    </t>
3193    <t>
3194      <eref target=""/>:
3195      "RFC2606 Compliance"
3196    </t>
3197    <t>
3198      <eref target=""/>:
3199      "Informative references"
3200    </t>
3201    <t>
3202      <eref target=""/>:
3203      "Redundant cross-references"
3204    </t>
3205  </list>
3208  Other changes:
3209  <list style="symbols">
3210    <t>
3211      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3212    </t>
3213  </list>
3217<section title="Since draft-ietf-httpbis-p2-semantics-01">
3219  Closed issues:
3220  <list style="symbols">
3221    <t>
3222      <eref target=""/>:
3223      "PUT side effects"
3224    </t>
3225    <t>
3226      <eref target=""/>:
3227      "Duplicate Host header requirements"
3228    </t>
3229  </list>
3232  Ongoing work on ABNF conversion (<eref target=""/>):
3233  <list style="symbols">
3234    <t>
3235      Move "Product Tokens" section (back) into Part 1, as "token" is used
3236      in the definition of the Upgrade header.
3237    </t>
3238    <t>
3239      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3240    </t>
3241    <t>
3242      Copy definition of delta-seconds from Part6 instead of referencing it.
3243    </t>
3244  </list>
3248<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3250  Closed issues:
3251  <list style="symbols">
3252    <t>
3253      <eref target=""/>:
3254      "Requiring Allow in 405 responses"
3255    </t>
3256    <t>
3257      <eref target=""/>:
3258      "Status Code Registry"
3259    </t>
3260    <t>
3261      <eref target=""/>:
3262      "Redirection vs. Location"
3263    </t>
3264    <t>
3265      <eref target=""/>:
3266      "Cacheability of 303 response"
3267    </t>
3268    <t>
3269      <eref target=""/>:
3270      "305 Use Proxy"
3271    </t>
3272    <t>
3273      <eref target=""/>:
3274      "Classification for Allow header"
3275    </t>
3276    <t>
3277      <eref target=""/>:
3278      "PUT - 'store under' vs 'store at'"
3279    </t>
3280  </list>
3283  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3284  <list style="symbols">
3285    <t>
3286      Reference RFC 3984, and update header registrations for headers defined
3287      in this document.
3288    </t>
3289  </list>
3292  Ongoing work on ABNF conversion (<eref target=""/>):
3293  <list style="symbols">
3294    <t>
3295      Replace string literals when the string really is case-sensitive (method).
3296    </t>
3297  </list>
3301<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3303  Closed issues:
3304  <list style="symbols">
3305    <t>
3306      <eref target=""/>:
3307      "OPTIONS request bodies"
3308    </t>
3309    <t>
3310      <eref target=""/>:
3311      "Description of CONNECT should refer to RFC2817"
3312    </t>
3313    <t>
3314      <eref target=""/>:
3315      "Location Content-Location reference request/response mixup"
3316    </t>
3317  </list>
3320  Ongoing work on Method Registry (<eref target=""/>):
3321  <list style="symbols">
3322    <t>
3323      Added initial proposal for registration process, plus initial
3324      content (non-HTTP/1.1 methods to be added by a separate specification).
3325    </t>
3326  </list>
3330<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3332  Closed issues:
3333  <list style="symbols">
3334    <t>
3335      <eref target=""/>:
3336      "Content-*"
3337    </t>
3338    <t>
3339      <eref target=""/>:
3340      "RFC 2822 is updated by RFC 5322"
3341    </t>
3342  </list>
3345  Ongoing work on ABNF conversion (<eref target=""/>):
3346  <list style="symbols">
3347    <t>
3348      Use "/" instead of "|" for alternatives.
3349    </t>
3350    <t>
3351      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3352      whitespace ("OWS") and required whitespace ("RWS").
3353    </t>
3354    <t>
3355      Rewrite ABNFs to spell out whitespace rules, factor out
3356      header value format definitions.
3357    </t>
3358  </list>
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