source: draft-ietf-httpbis/latest/p2-semantics.xml @ 391

Last change on this file since 391 was 391, checked in by julian.reschke@…, 14 years ago

Merge in Roy's changes wrt Introduction and HTTP Architecture, replace Request-URI by request-target and relative-URI by partial-URI throughout.

  • Property svn:eol-style set to native
File size: 144.4 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 uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
27  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
28  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
29  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
30  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
31  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
32  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
33  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
34  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
35  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
36  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
37  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
38  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
39  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
40  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
41  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
42  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
43  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
44  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
45  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
46  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
47  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
48  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
49  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
50  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
51  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
52  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
53  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
54  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
55  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
56  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
57  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
58  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
59  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
60  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
61  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
62  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
64<?rfc toc="yes" ?>
65<?rfc symrefs="yes" ?>
66<?rfc sortrefs="yes" ?>
67<?rfc compact="yes"?>
68<?rfc subcompact="no" ?>
69<?rfc linkmailto="no" ?>
70<?rfc editing="no" ?>
71<?rfc comments="yes"?>
72<?rfc inline="yes"?>
73<?rfc-ext allow-markup-in-artwork="yes" ?>
74<?rfc-ext include-references-in-index="yes" ?>
75<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
76     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
77     xmlns:x=''
78     xmlns:rdf=''>
81  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
83  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
84    <organization abbrev="Day Software">Day Software</organization>
85    <address>
86      <postal>
87        <street>23 Corporate Plaza DR, Suite 280</street>
88        <city>Newport Beach</city>
89        <region>CA</region>
90        <code>92660</code>
91        <country>USA</country>
92      </postal>
93      <phone>+1-949-706-5300</phone>
94      <facsimile>+1-949-706-5305</facsimile>
95      <email></email>
96      <uri></uri>
97    </address>
98  </author>
100  <author initials="J." surname="Gettys" fullname="Jim Gettys">
101    <organization>One Laptop per Child</organization>
102    <address>
103      <postal>
104        <street>21 Oak Knoll Road</street>
105        <city>Carlisle</city>
106        <region>MA</region>
107        <code>01741</code>
108        <country>USA</country>
109      </postal>
110      <email></email>
111      <uri></uri>
112    </address>
113  </author>
115  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
116    <organization abbrev="HP">Hewlett-Packard Company</organization>
117    <address>
118      <postal>
119        <street>HP Labs, Large Scale Systems Group</street>
120        <street>1501 Page Mill Road, MS 1177</street>
121        <city>Palo Alto</city>
122        <region>CA</region>
123        <code>94304</code>
124        <country>USA</country>
125      </postal>
126      <email></email>
127    </address>
128  </author>
130  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
131    <organization abbrev="Microsoft">Microsoft Corporation</organization>
132    <address>
133      <postal>
134        <street>1 Microsoft Way</street>
135        <city>Redmond</city>
136        <region>WA</region>
137        <code>98052</code>
138        <country>USA</country>
139      </postal>
140      <email></email>
141    </address>
142  </author>
144  <author initials="L." surname="Masinter" fullname="Larry Masinter">
145    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
146    <address>
147      <postal>
148        <street>345 Park Ave</street>
149        <city>San Jose</city>
150        <region>CA</region>
151        <code>95110</code>
152        <country>USA</country>
153      </postal>
154      <email></email>
155      <uri></uri>
156    </address>
157  </author>
159  <author initials="P." surname="Leach" fullname="Paul J. Leach">
160    <organization abbrev="Microsoft">Microsoft Corporation</organization>
161    <address>
162      <postal>
163        <street>1 Microsoft Way</street>
164        <city>Redmond</city>
165        <region>WA</region>
166        <code>98052</code>
167      </postal>
168      <email></email>
169    </address>
170  </author>
172  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
173    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
174    <address>
175      <postal>
176        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
177        <street>The Stata Center, Building 32</street>
178        <street>32 Vassar Street</street>
179        <city>Cambridge</city>
180        <region>MA</region>
181        <code>02139</code>
182        <country>USA</country>
183      </postal>
184      <email></email>
185      <uri></uri>
186    </address>
187  </author>
189  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
190    <organization abbrev="W3C">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>W3C / ERCIM</street>
194        <street>2004, rte des Lucioles</street>
195        <city>Sophia-Antipolis</city>
196        <region>AM</region>
197        <code>06902</code>
198        <country>France</country>
199      </postal>
200      <email></email>
201      <uri></uri>
202    </address>
203  </author>
205  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
206    <organization abbrev="greenbytes">greenbytes GmbH</organization>
207    <address>
208      <postal>
209        <street>Hafenweg 16</street>
210        <city>Muenster</city><region>NW</region><code>48155</code>
211        <country>Germany</country>
212      </postal>
213      <phone>+49 251 2807760</phone>   
214      <facsimile>+49 251 2807761</facsimile>   
215      <email></email>       
216      <uri></uri>     
217    </address>
218  </author>
220  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
224   The Hypertext Transfer Protocol (HTTP) is an application-level
225   protocol for distributed, collaborative, hypermedia information
226   systems. HTTP has been in use by the World Wide Web global information
227   initiative since 1990. This document is Part 2 of the seven-part specification
228   that defines the protocol referred to as "HTTP/1.1" and, taken together,
229   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
230   as expressed by request methods, request-header fields, response status codes,
231   and response-header fields.
235<note title="Editorial Note (To be removed by RFC Editor)">
236  <t>
237    Discussion of this draft should take place on the HTTPBIS working group
238    mailing list ( The current issues list is
239    at <eref target=""/>
240    and related documents (including fancy diffs) can be found at
241    <eref target=""/>.
242  </t>
243  <t>
244    The changes in this draft are summarized in <xref target="changes.since.05"/>.
245  </t>
249<section title="Introduction" anchor="introduction">
251   This document defines HTTP/1.1 request and response semantics.  Each HTTP
252   message, as defined in &messaging;, is in the form of either a request or
253   a response.  An HTTP server listens on a connection for HTTP requests and
254   responds to each request, in the order received on that connection, with
255   one or more HTTP response messages.  This document defines the commonly
256   agreed upon semantics of the HTTP uniform interface, the intentions defined
257   by each request method, and the various response messages that might be
258   expected as a result of applying that method for the requested resource.
261   This document is currently disorganized in order to minimize the changes
262   between drafts and enable reviewers to see the smaller errata changes.
263   The next draft will reorganize the sections to better reflect the content.
264   In particular, the sections will be ordered according to the typical
265   processing of an HTTP request message (after message parsing): resource
266   mapping, general header fields, methods, request modifiers, response
267   status, and resource metadata.  The current mess reflects how widely
268   dispersed these topics and associated requirements had become in
269   <xref target="RFC2616"/>.
272<section title="Requirements" anchor="intro.requirements">
274   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
275   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
276   document are to be interpreted as described in <xref target="RFC2119"/>.
279   An implementation is not compliant if it fails to satisfy one or more
280   of the &MUST; or &REQUIRED; level requirements for the protocols it
281   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
282   level and all the &SHOULD; level requirements for its protocols is said
283   to be "unconditionally compliant"; one that satisfies all the &MUST;
284   level requirements but not all the &SHOULD; level requirements for its
285   protocols is said to be "conditionally compliant."
290<section title="Notational Conventions and Generic Grammar" anchor="notation">
291  <x:anchor-alias value="comment"/>
292  <x:anchor-alias value="CR"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="LF"/>
295  <x:anchor-alias value="quoted-string"/>
296  <x:anchor-alias value="token"/>
297  <x:anchor-alias value="OWS"/>
298  <x:anchor-alias value="RWS"/>
299  <x:anchor-alias value="TEXT"/>
301  This specification uses the ABNF syntax defined in &notation-abnf; and
302  the core rules defined in &basic-rules;:
304<figure><artwork type="abnf2616">
305  <x:ref>CR</x:ref>            = &lt;CR, defined in &basic-rules;&gt;
306  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
307  <x:ref>LF</x:ref>            = &lt;LF, defined in &basic-rules;&gt;
309<figure><artwork type="abnf2616">
310  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
311  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
312  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
313  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
314  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
315  <x:ref>TEXT</x:ref>          = &lt;TEXT, defined in &basic-rules;&gt;
317<t anchor="abnf.dependencies">
318  <x:anchor-alias value="absolute-URI"/>
319  <x:anchor-alias value="Accept"/>
320  <x:anchor-alias value="Accept-Charset"/>
321  <x:anchor-alias value="Accept-Encoding"/>
322  <x:anchor-alias value="Accept-Language"/>
323  <x:anchor-alias value="Accept-Ranges"/>
324  <x:anchor-alias value="Age"/>
325  <x:anchor-alias value="Authorization"/>
326  <x:anchor-alias value="ETag"/>
327  <x:anchor-alias value="fragment"/>
328  <x:anchor-alias value="Host"/>
329  <x:anchor-alias value="HTTP-date"/>
330  <x:anchor-alias value="If-Match"/>
331  <x:anchor-alias value="If-Modified-Since"/>
332  <x:anchor-alias value="If-None-Match"/>
333  <x:anchor-alias value="If-Range"/>
334  <x:anchor-alias value="If-Unmodified-Since"/>
335  <x:anchor-alias value="partial-URI"/>
336  <x:anchor-alias value="product"/>
337  <x:anchor-alias value="Proxy-Authenticate"/>
338  <x:anchor-alias value="Proxy-Authorization"/>
339  <x:anchor-alias value="Range"/>
340  <x:anchor-alias value="TE"/>
341  <x:anchor-alias value="Vary"/>
342  <x:anchor-alias value="WWW-Authenticate"/>
343  The ABNF rules below are defined in other parts:
345<figure><!--Part1--><artwork type="abnf2616">
346  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
347  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
348  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
349  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
350  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
351  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
352  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
354<figure><!--Part3--><artwork type="abnf2616">
355  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
356  <x:ref>Accept-Charset</x:ref> =
357             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
358  <x:ref>Accept-Encoding</x:ref> =
359             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
360  <x:ref>Accept-Language</x:ref> =
361             &lt;Accept-Language, defined in &header-accept-language;&gt;
363<figure><!--Part4--><artwork type="abnf2616">
364  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
365  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
366  <x:ref>If-Modified-Since</x:ref> =
367             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
368  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
369  <x:ref>If-Unmodified-Since</x:ref> =
370             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
372<figure><!--Part5--><artwork type="abnf2616">
373  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
374  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
375  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
377<figure><!--Part6--><artwork type="abnf2616">
378  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
379  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
381<figure><artwork type="abnf2616">
382  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
383  <x:ref>Proxy-Authenticate</x:ref> =
384             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
385  <x:ref>Proxy-Authorization</x:ref> =
386             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
387  <x:ref>WWW-Authenticate</x:ref> =
388             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
392<section title="Method" anchor="method">
393  <x:anchor-alias value="Method"/>
394  <x:anchor-alias value="extension-method"/>
396   The Method  token indicates the method to be performed on the
397   resource identified by the request-target. The method is case-sensitive.
399<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
400  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
401                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
402                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
403                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
404                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
405                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
406                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
407                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
408                 / <x:ref>extension-method</x:ref>
409  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
412   The list of methods allowed by a resource can be specified in an
413   Allow header field (<xref target="header.allow"/>). The return code of the response
414   always notifies the client whether a method is currently allowed on a
415   resource, since the set of allowed methods can change dynamically. An
416   origin server &SHOULD; return the status code 405 (Method Not Allowed)
417   if the method is known by the origin server but not allowed for the
418   requested resource, and 501 (Not Implemented) if the method is
419   unrecognized or not implemented by the origin server. The methods GET
420   and HEAD &MUST; be supported by all general-purpose servers. All other
421   methods are &OPTIONAL;; however, if the above methods are implemented,
422   they &MUST; be implemented with the same semantics as those specified
423   in <xref target="method.definitions"/>.
426<section title="Method Registry" anchor="method.registry">
428  The HTTP Method Registry defines the name space for the Method token in the
429  Request line of an HTTP request.
432  Registrations &MUST; include the following fields:
433  <list style="symbols">
434    <t>Method Name (see <xref target="method"/>)</t>
435    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
436    <t>Pointer to specification text</t>
437  </list>
440  Values to be added to this name space are subject to IETF review
441  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
442  new method names should be traceable through statuses of either 'Obsoletes'
443  or 'Updates' to this document.
446  The registry itself is maintained at <eref target=""/>.
451<section title="Request Header Fields" anchor="request.header.fields">
452  <x:anchor-alias value="extension-code"/>
453  <x:anchor-alias value="request-header"/>
455   The request-header fields allow the client to pass additional
456   information about the request, and about the client itself, to the
457   server. These fields act as request modifiers, with semantics
458   equivalent to the parameters on a programming language method
459   invocation.
461<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
462  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
463                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
464                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
465                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
466                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
467                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
468                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
469                 / <x:ref>Host</x:ref>                     ; &header-host;
470                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
471                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
472                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
473                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
474                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
475                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
476                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
477                 / <x:ref>Range</x:ref>                    ; &header-range;
478                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
479                 / <x:ref>TE</x:ref>                       ; &header-te;
480                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
483   Request-header field names can be extended reliably only in
484   combination with a change in the protocol version. However, new or
485   experimental header fields &MAY; be given the semantics of request-header
486   fields if all parties in the communication recognize them to
487   be request-header fields. Unrecognized header fields are treated as
488   entity-header fields.
492<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
493  <x:anchor-alias value="Reason-Phrase"/>
494  <x:anchor-alias value="Status-Code"/>
496   The Status-Code element is a 3-digit integer result code of the
497   attempt to understand and satisfy the request. The status codes listed
498   below are defined in <xref target=""/>.
499   The Reason-Phrase is intended to give a short
500   textual description of the Status-Code. The Status-Code is intended
501   for use by automata and the Reason-Phrase is intended for the human
502   user. The client is not required to examine or display the Reason-Phrase.
505   The individual values of the numeric status codes defined for
506   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
507   presented below. The reason phrases listed here are only
508   recommendations -- they &MAY; be replaced by local equivalents without
509   affecting the protocol.
511<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"/>
512  <x:ref>Status-Code</x:ref>    =
513         "100"  ; <xref target="status.100"/>: Continue
514       / "101"  ; <xref target="status.101"/>: Switching Protocols
515       / "200"  ; <xref target="status.200"/>: OK
516       / "201"  ; <xref target="status.201"/>: Created
517       / "202"  ; <xref target="status.202"/>: Accepted
518       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
519       / "204"  ; <xref target="status.204"/>: No Content
520       / "205"  ; <xref target="status.205"/>: Reset Content
521       / "206"  ; <xref target="status.206"/>: Partial Content
522       / "300"  ; <xref target="status.300"/>: Multiple Choices
523       / "301"  ; <xref target="status.301"/>: Moved Permanently
524       / "302"  ; <xref target="status.302"/>: Found
525       / "303"  ; <xref target="status.303"/>: See Other
526       / "304"  ; <xref target="status.304"/>: Not Modified
527       / "305"  ; <xref target="status.305"/>: Use Proxy
528       / "307"  ; <xref target="status.307"/>: Temporary Redirect
529       / "400"  ; <xref target="status.400"/>: Bad Request
530       / "401"  ; <xref target="status.401"/>: Unauthorized
531       / "402"  ; <xref target="status.402"/>: Payment Required
532       / "403"  ; <xref target="status.403"/>: Forbidden
533       / "404"  ; <xref target="status.404"/>: Not Found
534       / "405"  ; <xref target="status.405"/>: Method Not Allowed
535       / "406"  ; <xref target="status.406"/>: Not Acceptable
536       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
537       / "408"  ; <xref target="status.408"/>: Request Time-out
538       / "409"  ; <xref target="status.409"/>: Conflict
539       / "410"  ; <xref target="status.410"/>: Gone
540       / "411"  ; <xref target="status.411"/>: Length Required
541       / "412"  ; <xref target="status.412"/>: Precondition Failed
542       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
543       / "414"  ; <xref target="status.414"/>: Request-target Too Large
544       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
545       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
546       / "417"  ; <xref target="status.417"/>: Expectation Failed
547       / "500"  ; <xref target="status.500"/>: Internal Server Error
548       / "501"  ; <xref target="status.501"/>: Not Implemented
549       / "502"  ; <xref target="status.502"/>: Bad Gateway
550       / "503"  ; <xref target="status.503"/>: Service Unavailable
551       / "504"  ; <xref target="status.504"/>: Gateway Time-out
552       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
553       / <x:ref>extension-code</x:ref>
555  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
556  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
559   HTTP status codes are extensible. HTTP applications are not required
560   to understand the meaning of all registered status codes, though such
561   understanding is obviously desirable. However, applications &MUST;
562   understand the class of any status code, as indicated by the first
563   digit, and treat any unrecognized response as being equivalent to the
564   x00 status code of that class, with the exception that an
565   unrecognized response &MUST-NOT; be cached. For example, if an
566   unrecognized status code of 431 is received by the client, it can
567   safely assume that there was something wrong with its request and
568   treat the response as if it had received a 400 status code. In such
569   cases, user agents &SHOULD; present to the user the entity returned
570   with the response, since that entity is likely to include human-readable
571   information which will explain the unusual status.
574<section title="Status Code Registry" anchor="status.code.registry">
576  The HTTP Status Code Registry defines the name space for the Status-Code
577  token in the Status line of an HTTP response.
580  Values to be added to this name space are subject to IETF review
581  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
582  new status codes should be traceable through statuses of either 'Obsoletes'
583  or 'Updates' to this document.
586  The registry itself is maintained at <eref target=""/>.
592<section title="Response Header Fields" anchor="response.header.fields">
593  <x:anchor-alias value="response-header"/>
595   The response-header fields allow the server to pass additional
596   information about the response which cannot be placed in the Status-Line.
597   These header fields give information about the server and about
598   further access to the resource identified by the request-target.
600<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
601  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
602                  / <x:ref>Age</x:ref>                     ; &header-age;
603                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
604                  / <x:ref>ETag</x:ref>                    ; &header-etag;
605                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
606                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
607                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
608                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
609                  / <x:ref>Vary</x:ref>                    ; &header-vary;
610                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
613   Response-header field names can be extended reliably only in
614   combination with a change in the protocol version. However, new or
615   experimental header fields &MAY; be given the semantics of response-header
616   fields if all parties in the communication recognize them to
617   be response-header fields. Unrecognized header fields are treated as
618   entity-header fields.
622<section title="Entity" anchor="entity">
624   Request and Response messages &MAY; transfer an entity if not otherwise
625   restricted by the request method or response status code. An entity
626   consists of entity-header fields and an entity-body, although some
627   responses will only include the entity-headers. HTTP entity-body and
628   entity-header fields are defined in &payload;.
631   An entity-body is only present in a message when a message-body is
632   present, as described in &message-body;. The entity-body is obtained
633   from the message-body by decoding any Transfer-Encoding that might
634   have been applied to ensure safe and proper transfer of the message.
639<section title="Method Definitions" anchor="method.definitions">
641   The set of common methods for HTTP/1.1 is defined below. Although
642   this set can be expanded, additional methods cannot be assumed to
643   share the same semantics for separately extended clients and servers.
646<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
648<section title="Safe Methods" anchor="safe.methods">
649<iref item="Safe Methods" primary="true"/>
651   Implementors should be aware that the software represents the user in
652   their interactions over the Internet, and should be careful to allow
653   the user to be aware of any actions they might take which may have an
654   unexpected significance to themselves or others.
657   In particular, the convention has been established that the GET and
658   HEAD methods &SHOULD-NOT;  have the significance of taking an action
659   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
660   This allows user agents to represent other methods, such as POST, PUT
661   and DELETE, in a special way, so that the user is made aware of the
662   fact that a possibly unsafe action is being requested.
665   Naturally, it is not possible to ensure that the server does not
666   generate side-effects as a result of performing a GET request; in
667   fact, some dynamic resources consider that a feature. The important
668   distinction here is that the user did not request the side-effects,
669   so therefore cannot be held accountable for them.
673<section title="Idempotent Methods" anchor="idempotent.methods">
674<iref item="Idempotent Methods" primary="true"/>
676   Methods can also have the property of "idempotence" in that (aside
677   from error or expiration issues) the side-effects of N &gt; 0 identical
678   requests is the same as for a single request. The methods GET, HEAD,
679   PUT and DELETE share this property. Also, the methods OPTIONS and
680   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
683   However, it is possible that a sequence of several requests is non-idempotent,
684   even if all of the methods executed in that sequence are
685   idempotent. (A sequence is idempotent if a single execution of the
686   entire sequence always yields a result that is not changed by a
687   reexecution of all, or part, of that sequence.) For example, a
688   sequence is non-idempotent if its result depends on a value that is
689   later modified in the same sequence.
692   A sequence that never has side effects is idempotent, by definition
693   (provided that no concurrent operations are being executed on the
694   same set of resources).
699<section title="OPTIONS" anchor="OPTIONS">
700  <rdf:Description>
701    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
702  </rdf:Description>
703  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
704  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
706   The OPTIONS method represents a request for information about the
707   communication options available on the request/response chain
708   identified by the request-target. This method allows the client to
709   determine the options and/or requirements associated with a resource,
710   or the capabilities of a server, without implying a resource action
711   or initiating a resource retrieval.
714   Responses to this method are not cacheable.
717   If the OPTIONS request includes an entity-body (as indicated by the
718   presence of Content-Length or Transfer-Encoding), then the media type
719   &MUST; be indicated by a Content-Type field. Although this
720   specification does not define any use for such a body, future
721   extensions to HTTP might use the OPTIONS body to make more detailed
722   queries on the server.
725   If the request-target is an asterisk ("*"), the OPTIONS request is
726   intended to apply to the server in general rather than to a specific
727   resource. Since a server's communication options typically depend on
728   the resource, the "*" request is only useful as a "ping" or "no-op"
729   type of method; it does nothing beyond allowing the client to test
730   the capabilities of the server. For example, this can be used to test
731   a proxy for HTTP/1.1 compliance (or lack thereof).
734   If the request-target is not an asterisk, the OPTIONS request applies
735   only to the options that are available when communicating with that
736   resource.
739   A 200 response &SHOULD; include any header fields that indicate
740   optional features implemented by the server and applicable to that
741   resource (e.g., Allow), possibly including extensions not defined by
742   this specification. The response body, if any, &SHOULD; also include
743   information about the communication options. The format for such a
744   body is not defined by this specification, but might be defined by
745   future extensions to HTTP. Content negotiation &MAY; be used to select
746   the appropriate response format. If no response body is included, the
747   response &MUST; include a Content-Length field with a field-value of
748   "0".
751   The Max-Forwards request-header field &MAY; be used to target a
752   specific proxy in the request chain. When a proxy receives an OPTIONS
753   request on an absolute-URI for which request forwarding is permitted,
754   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
755   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
756   instead, the proxy &SHOULD; respond with its own communication options.
757   If the Max-Forwards field-value is an integer greater than zero, the
758   proxy &MUST; decrement the field-value when it forwards the request. If
759   no Max-Forwards field is present in the request, then the forwarded
760   request &MUST-NOT; include a Max-Forwards field.
764<section title="GET" anchor="GET">
765  <rdf:Description>
766    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
767  </rdf:Description>
768  <iref primary="true" item="GET method" x:for-anchor=""/>
769  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
771   The GET method means retrieve whatever information (in the form of an
772   entity) is identified by the request-target. If the request-target refers
773   to a data-producing process, it is the produced data which shall be
774   returned as the entity in the response and not the source text of the
775   process, unless that text happens to be the output of the process.
778   The semantics of the GET method change to a "conditional GET" if the
779   request message includes an If-Modified-Since, If-Unmodified-Since,
780   If-Match, If-None-Match, or If-Range header field. A conditional GET
781   method requests that the entity be transferred only under the
782   circumstances described by the conditional header field(s). The
783   conditional GET method is intended to reduce unnecessary network
784   usage by allowing cached entities to be refreshed without requiring
785   multiple requests or transferring data already held by the client.
788   The semantics of the GET method change to a "partial GET" if the
789   request message includes a Range header field. A partial GET requests
790   that only part of the entity be transferred, as described in &header-range;.
791   The partial GET method is intended to reduce unnecessary
792   network usage by allowing partially-retrieved entities to be
793   completed without transferring data already held by the client.
796   The response to a GET request is cacheable if and only if it meets
797   the requirements for HTTP caching described in &caching;.
800   See <xref target=""/> for security considerations when used for forms.
804<section title="HEAD" anchor="HEAD">
805  <rdf:Description>
806    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
807  </rdf:Description>
808  <iref primary="true" item="HEAD method" x:for-anchor=""/>
809  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
811   The HEAD method is identical to GET except that the server &MUST-NOT;
812   return a message-body in the response. The metainformation contained
813   in the HTTP headers in response to a HEAD request &SHOULD; be identical
814   to the information sent in response to a GET request. This method can
815   be used for obtaining metainformation about the entity implied by the
816   request without transferring the entity-body itself. This method is
817   often used for testing hypertext links for validity, accessibility,
818   and recent modification.
821   The response to a HEAD request &MAY; be cacheable in the sense that the
822   information contained in the response &MAY; be used to update a
823   previously cached entity from that resource. If the new field values
824   indicate that the cached entity differs from the current entity (as
825   would be indicated by a change in Content-Length, Content-MD5, ETag
826   or Last-Modified), then the cache &MUST; treat the cache entry as
827   stale.
831<section title="POST" anchor="POST">
832  <iref primary="true" item="POST method" x:for-anchor=""/>
833  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
835   The POST method is used to request that the origin server accept the
836   entity enclosed in the request as data to be processed by the resource
837   identified by the request-target in the Request-Line. POST is designed
838   to allow a uniform method to cover the following functions:
839  <list style="symbols">
840    <t>
841      Annotation of existing resources;
842    </t>
843    <t>
844        Posting a message to a bulletin board, newsgroup, mailing list,
845        or similar group of articles;
846    </t>
847    <t>
848        Providing a block of data, such as the result of submitting a
849        form, to a data-handling process;
850    </t>
851    <t>
852        Extending a database through an append operation.
853    </t>
854  </list>
857   The actual function performed by the POST method is determined by the
858   server and is usually dependent on the request-target.
861   The action performed by the POST method might not result in a
862   resource that can be identified by a URI. In this case, either 200
863   (OK) or 204 (No Content) is the appropriate response status,
864   depending on whether or not the response includes an entity that
865   describes the result.
868   If a resource has been created on the origin server, the response
869   &SHOULD; be 201 (Created) and contain an entity which describes the
870   status of the request and refers to the new resource, and a Location
871   header (see <xref target="header.location"/>).
874   Responses to this method are not cacheable, unless the response
875   includes appropriate Cache-Control or Expires header fields. However,
876   the 303 (See Other) response can be used to direct the user agent to
877   retrieve a cacheable resource.
881<section title="PUT" anchor="PUT">
882  <iref primary="true" item="PUT method" x:for-anchor=""/>
883  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
885   The PUT method requests that the enclosed entity be stored at the
886   supplied request-target. If the request-target refers to an already
887   existing resource, the enclosed entity &SHOULD; be considered as a
888   modified version of the one residing on the origin server. If the
889   request-target does not point to an existing resource, and that URI is
890   capable of being defined as a new resource by the requesting user
891   agent, the origin server can create the resource with that URI. If a
892   new resource is created at the request-target, the origin server &MUST;
893         inform the user agent
894   via the 201 (Created) response. If an existing resource is modified,
895   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
896   to indicate successful completion of the request. If the resource
897   could not be created or modified with the request-target, an appropriate
898   error response &SHOULD; be given that reflects the nature of the
899   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
900   headers (headers starting with the prefix 'Content-') that it does
901   not understand or implement
902   and &MUST; return a 501 (Not Implemented) response in such cases.
905   If the request passes through a cache and the request-target identifies
906   one or more currently cached entities, those entries &SHOULD; be
907   treated as stale. Responses to this method are not cacheable.
910   The fundamental difference between the POST and PUT requests is
911   reflected in the different meaning of the request-target. The URI in a
912   POST request identifies the resource that will handle the enclosed
913   entity. That resource might be a data-accepting process, a gateway to
914   some other protocol, or a separate entity that accepts annotations.
915   In contrast, the URI in a PUT request identifies the entity enclosed
916   with the request -- the user agent knows what URI is intended and the
917   server &MUST-NOT; attempt to apply the request to some other resource.
918   If the server desires that the request be applied to a different URI,
919   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
920   then make its own decision regarding whether or not to redirect the
921   request.
924   A single resource &MAY; be identified by many different URIs. For
925   example, an article might have a URI for identifying "the current
926   version" which is separate from the URI identifying each particular
927   version. In this case, a PUT request on a general URI might result in
928   several other URIs being defined by the origin server.
931   HTTP/1.1 does not define how a PUT method affects the state of an
932   origin server.
935   Unless otherwise specified for a particular entity-header, the
936   entity-headers in the PUT request &SHOULD; be applied to the resource
937   created or modified by the PUT.
941<section title="DELETE" anchor="DELETE">
942  <iref primary="true" item="DELETE method" x:for-anchor=""/>
943  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
945   The DELETE method requests that the origin server delete the resource
946   identified by the request-target. This method &MAY; be overridden by human
947   intervention (or other means) on the origin server. The client cannot
948   be guaranteed that the operation has been carried out, even if the
949   status code returned from the origin server indicates that the action
950   has been completed successfully. However, the server &SHOULD-NOT;
951   indicate success unless, at the time the response is given, it
952   intends to delete the resource or move it to an inaccessible
953   location.
956   A successful response &SHOULD; be 200 (OK) if the response includes an
957   entity describing the status, 202 (Accepted) if the action has not
958   yet been enacted, or 204 (No Content) if the action has been enacted
959   but the response does not include an entity.
962   If the request passes through a cache and the request-target identifies
963   one or more currently cached entities, those entries &SHOULD; be
964   treated as stale. Responses to this method are not cacheable.
968<section title="TRACE" anchor="TRACE">
969  <rdf:Description>
970    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
971  </rdf:Description>
972  <iref primary="true" item="TRACE method" x:for-anchor=""/>
973  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
975   The TRACE method is used to invoke a remote, application-layer loop-back
976   of the request message. The final recipient of the request
977   &SHOULD; reflect the message received back to the client as the
978   entity-body of a 200 (OK) response. The final recipient is either the
979   origin server or the first proxy or gateway to receive a Max-Forwards
980   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
981   &MUST-NOT; include an entity.
984   TRACE allows the client to see what is being received at the other
985   end of the request chain and use that data for testing or diagnostic
986   information. The value of the Via header field (&header-via;) is of
987   particular interest, since it acts as a trace of the request chain.
988   Use of the Max-Forwards header field allows the client to limit the
989   length of the request chain, which is useful for testing a chain of
990   proxies forwarding messages in an infinite loop.
993   If the request is valid, the response &SHOULD; contain the entire
994   request message in the entity-body, with a Content-Type of
995   "message/http" (see &media-type-message-http;). Responses to this method
996   &MUST-NOT; be cached.
1000<section title="CONNECT" anchor="CONNECT">
1001  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1002  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1004   This specification reserves the method name CONNECT for use with a
1005   proxy that can dynamically switch to being a tunnel (e.g. SSL
1006   tunneling <xref target="RFC2817"/>).
1012<section title="Status Code Definitions" anchor="">
1014   Each Status-Code is described below, including a description of which
1015   method(s) it can follow and any metainformation required in the
1016   response.
1019<section title="Informational 1xx" anchor="status.1xx">
1021   This class of status code indicates a provisional response,
1022   consisting only of the Status-Line and optional headers, and is
1023   terminated by an empty line. There are no required headers for this
1024   class of status code. Since HTTP/1.0 did not define any 1xx status
1025   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1026   except under experimental conditions.
1029   A client &MUST; be prepared to accept one or more 1xx status responses
1030   prior to a regular response, even if the client does not expect a 100
1031   (Continue) status message. Unexpected 1xx status responses &MAY; be
1032   ignored by a user agent.
1035   Proxies &MUST; forward 1xx responses, unless the connection between the
1036   proxy and its client has been closed, or unless the proxy itself
1037   requested the generation of the 1xx response. (For example, if a
1038   proxy adds a "Expect: 100-continue" field when it forwards a request,
1039   then it need not forward the corresponding 100 (Continue)
1040   response(s).)
1043<section title="100 Continue" anchor="status.100">
1044  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1045  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1047   The client &SHOULD; continue with its request. This interim response is
1048   used to inform the client that the initial part of the request has
1049   been received and has not yet been rejected by the server. The client
1050   &SHOULD; continue by sending the remainder of the request or, if the
1051   request has already been completed, ignore this response. The server
1052   &MUST; send a final response after the request has been completed. See
1053   &use100; for detailed discussion of the use and handling of this
1054   status code.
1058<section title="101 Switching Protocols" anchor="status.101">
1059  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1060  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1062   The server understands and is willing to comply with the client's
1063   request, via the Upgrade message header field (&header-upgrade;), for a
1064   change in the application protocol being used on this connection. The
1065   server will switch protocols to those defined by the response's
1066   Upgrade header field immediately after the empty line which
1067   terminates the 101 response.
1070   The protocol &SHOULD; be switched only when it is advantageous to do
1071   so. For example, switching to a newer version of HTTP is advantageous
1072   over older versions, and switching to a real-time, synchronous
1073   protocol might be advantageous when delivering resources that use
1074   such features.
1079<section title="Successful 2xx" anchor="status.2xx">
1081   This class of status code indicates that the client's request was
1082   successfully received, understood, and accepted.
1085<section title="200 OK" anchor="status.200">
1086  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1087  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1089   The request has succeeded. The information returned with the response
1090   is dependent on the method used in the request, for example:
1091  <list style="hanging">
1092    <t hangText="GET">
1093          an entity corresponding to the requested resource is sent in
1094          the response;
1095    </t>
1096    <t hangText="HEAD">
1097          the entity-header fields corresponding to the requested
1098          resource are sent in the response without any message-body;
1099    </t>
1100    <t hangText="POST">
1101      an entity describing or containing the result of the action;
1102    </t>
1103    <t hangText="TRACE">
1104      an entity containing the request message as received by the
1105      end server.
1106    </t>
1107  </list>
1111<section title="201 Created" anchor="status.201">
1112  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1113  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1115   The request has been fulfilled and resulted in a new resource being
1116   created. The newly created resource can be referenced by the URI(s)
1117   returned in the entity of the response, with the most specific URI
1118   for the resource given by a Location header field. The response
1119   &SHOULD; include an entity containing a list of resource
1120   characteristics and location(s) from which the user or user agent can
1121   choose the one most appropriate. The entity format is specified by
1122   the media type given in the Content-Type header field. The origin
1123   server &MUST; create the resource before returning the 201 status code.
1124   If the action cannot be carried out immediately, the server &SHOULD;
1125   respond with 202 (Accepted) response instead.
1128   A 201 response &MAY; contain an ETag response header field indicating
1129   the current value of the entity tag for the requested variant just
1130   created, see &header-etag;.
1134<section title="202 Accepted" anchor="status.202">
1135  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1136  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1138   The request has been accepted for processing, but the processing has
1139   not been completed.  The request might or might not eventually be
1140   acted upon, as it might be disallowed when processing actually takes
1141   place. There is no facility for re-sending a status code from an
1142   asynchronous operation such as this.
1145   The 202 response is intentionally non-committal. Its purpose is to
1146   allow a server to accept a request for some other process (perhaps a
1147   batch-oriented process that is only run once per day) without
1148   requiring that the user agent's connection to the server persist
1149   until the process is completed. The entity returned with this
1150   response &SHOULD; include an indication of the request's current status
1151   and either a pointer to a status monitor or some estimate of when the
1152   user can expect the request to be fulfilled.
1156<section title="203 Non-Authoritative Information" anchor="status.203">
1157  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1158  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1160   The returned metainformation in the entity-header is not the
1161   definitive set as available from the origin server, but is gathered
1162   from a local or a third-party copy. The set presented &MAY; be a subset
1163   or superset of the original version. For example, including local
1164   annotation information about the resource might result in a superset
1165   of the metainformation known by the origin server. Use of this
1166   response code is not required and is only appropriate when the
1167   response would otherwise be 200 (OK).
1171<section title="204 No Content" anchor="status.204">
1172  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1173  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1175   The server has fulfilled the request but does not need to return an
1176   entity-body, and might want to return updated metainformation. The
1177   response &MAY; include new or updated metainformation in the form of
1178   entity-headers, which if present &SHOULD; be associated with the
1179   requested variant.
1182   If the client is a user agent, it &SHOULD-NOT;  change its document view
1183   from that which caused the request to be sent. This response is
1184   primarily intended to allow input for actions to take place without
1185   causing a change to the user agent's active document view, although
1186   any new or updated metainformation &SHOULD; be applied to the document
1187   currently in the user agent's active view.
1190   The 204 response &MUST-NOT; include a message-body, and thus is always
1191   terminated by the first empty line after the header fields.
1195<section title="205 Reset Content" anchor="status.205">
1196  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1197  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1199   The server has fulfilled the request and the user agent &SHOULD; reset
1200   the document view which caused the request to be sent. This response
1201   is primarily intended to allow input for actions to take place via
1202   user input, followed by a clearing of the form in which the input is
1203   given so that the user can easily initiate another input action. The
1204   response &MUST-NOT; include an entity.
1208<section title="206 Partial Content" anchor="status.206">
1209  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1210  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1212   The server has fulfilled the partial GET request for the resource
1213   and the enclosed entity is a partial representation as defined in &range;.
1218<section title="Redirection 3xx" anchor="status.3xx">
1220   This class of status code indicates that further action needs to be
1221   taken by the user agent in order to fulfill the request.  The action
1222   required &MAY; be carried out by the user agent without interaction
1223   with the user if and only if the method used in the second request is
1224   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1225   such loops generate network traffic for each redirection.
1226  <list><t>
1227      <x:h>Note:</x:h> previous versions of this specification recommended a
1228      maximum of five redirections. Content developers should be aware
1229      that there might be clients that implement such a fixed
1230      limitation.
1231  </t></list>
1234<section title="300 Multiple Choices" anchor="status.300">
1235  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1236  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1238   The requested resource corresponds to any one of a set of
1239   representations, each with its own specific location, and agent-driven
1240   negotiation information (&content-negotiation;) is being provided so that
1241   the user (or user agent) can select a preferred representation and
1242   redirect its request to that location.
1245   Unless it was a HEAD request, the response &SHOULD; include an entity
1246   containing a list of resource characteristics and location(s) from
1247   which the user or user agent can choose the one most appropriate. The
1248   entity format is specified by the media type given in the Content-Type
1249   header field. Depending upon the format and the capabilities of
1250   the user agent, selection of the most appropriate choice &MAY; be
1251   performed automatically. However, this specification does not define
1252   any standard for such automatic selection.
1255   If the server has a preferred choice of representation, it &SHOULD;
1256   include the specific URI for that representation in the Location
1257   field; user agents &MAY; use the Location field value for automatic
1258   redirection. This response is cacheable unless indicated otherwise.
1262<section title="301 Moved Permanently" anchor="status.301">
1263  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1264  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1266   The requested resource has been assigned a new permanent URI and any
1267   future references to this resource &SHOULD; use one of the returned
1268   URIs.  Clients with link editing capabilities ought to automatically
1269   re-link references to the request-target to one or more of the new
1270   references returned by the server, where possible. This response is
1271   cacheable unless indicated otherwise.
1274   The new permanent URI &SHOULD; be given by the Location field in the
1275   response. Unless the request method was HEAD, the entity of the
1276   response &SHOULD; contain a short hypertext note with a hyperlink to
1277   the new URI(s).
1280   If the 301 status code is received in response to a request method
1281   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1282   then the request &MAY; be automatically redirected by the user agent without
1283   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1284   request unless it can be confirmed by the user, since this might
1285   change the conditions under which the request was issued.
1286  <list><t>
1287      <x:h>Note:</x:h> When automatically redirecting a POST request after
1288      receiving a 301 status code, some existing HTTP/1.0 user agents
1289      will erroneously change it into a GET request.
1290  </t></list>
1294<section title="302 Found" anchor="status.302">
1295  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1296  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1298   The requested resource resides temporarily under a different URI.
1299   Since the redirection might be altered on occasion, the client &SHOULD;
1300   continue to use the request-target for future requests.  This response
1301   is only cacheable if indicated by a Cache-Control or Expires header
1302   field.
1305   The temporary URI &SHOULD; be given by the Location field in the
1306   response. Unless the request method was HEAD, the entity of the
1307   response &SHOULD; contain a short hypertext note with a hyperlink to
1308   the new URI(s).
1311   If the 302 status code is received in response to a request method
1312   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1313   then the request &MAY; be automatically redirected by the user agent without
1314   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1315   request unless it can be confirmed by the user, since this might
1316   change the conditions under which the request was issued.
1317  <list><t>
1318      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1319      to change the method on the redirected request.  However, most
1320      existing user agent implementations treat 302 as if it were a 303
1321      response, performing a GET on the Location field-value regardless
1322      of the original request method. The status codes 303 and 307 have
1323      been added for servers that wish to make unambiguously clear which
1324      kind of reaction is expected of the client.
1325  </t></list>
1329<section title="303 See Other" anchor="status.303">
1330  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1331  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1333   The server directs the user agent to a different resource, indicated
1334   by a URI in the Location header field, that provides an indirect
1335   response to the original request.  The user agent &MAY; perform a GET
1336   request on the URI in the Location field in order to obtain a
1337   representation corresponding to the response, be redirected again,
1338   or end with an error status.  The Location URI is not a substitute
1339   reference for the originally requested resource.
1342   The 303 status is generally applicable to any HTTP method.  It is
1343   primarily used to allow the output of a POST action to redirect
1344   the user agent to a selected resource, since doing so provides the
1345   information corresponding to the POST response in a form that
1346   can be separately identified, bookmarked, and cached independent
1347   of the original request.
1350   A 303 response to a GET request indicates that the requested
1351   resource does not have a representation of its own that can be
1352   transferred by the server over HTTP.  The Location URI indicates a
1353   resource that is descriptive of the requested resource such that
1354   the follow-on representation may be useful without implying that
1355   it adequately represents the previously requested resource.
1356   Note that answers to the questions of what can be represented, what
1357   representations are adequate, and what might be a useful description
1358   are outside the scope of HTTP and thus entirely determined by the
1359   resource owner(s).
1362   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1363   cacheable by Cache-Control or Expires header fields.  Except for
1364   responses to a HEAD request, the entity of a 303 response &SHOULD;
1365   contain a short hypertext note with a hyperlink to the Location URI.
1369<section title="304 Not Modified" anchor="status.304">
1370  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1371  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1373   The response to the request has not been modified since the conditions
1374   indicated by the client's conditional GET request, as defined in &conditional;.
1378<section title="305 Use Proxy" anchor="status.305">
1379  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1380  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1382   The 305 status was defined in a previous version of this specification
1383   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1387<section title="306 (Unused)" anchor="status.306">
1388  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1389  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1391   The 306 status code was used in a previous version of the
1392   specification, is no longer used, and the code is reserved.
1396<section title="307 Temporary Redirect" anchor="status.307">
1397  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1398  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1400   The requested resource resides temporarily under a different URI.
1401   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1402   continue to use the request-target for future requests.  This response
1403   is only cacheable if indicated by a Cache-Control or Expires header
1404   field.
1407   The temporary URI &SHOULD; be given by the Location field in the
1408   response. Unless the request method was HEAD, the entity of the
1409   response &SHOULD; contain a short hypertext note with a hyperlink to
1410   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1411   understand the 307 status. Therefore, the note &SHOULD; contain the
1412   information necessary for a user to repeat the original request on
1413   the new URI.
1416   If the 307 status code is received in response to a request method
1417   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1418   then the request &MAY; be automatically redirected by the user agent without
1419   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1420   request unless it can be confirmed by the user, since this might
1421   change the conditions under which the request was issued.
1426<section title="Client Error 4xx" anchor="status.4xx">
1428   The 4xx class of status code is intended for cases in which the
1429   client seems to have erred. Except when responding to a HEAD request,
1430   the server &SHOULD; include an entity containing an explanation of the
1431   error situation, and whether it is a temporary or permanent
1432   condition. These status codes are applicable to any request method.
1433   User agents &SHOULD; display any included entity to the user.
1436   If the client is sending data, a server implementation using TCP
1437   &SHOULD; be careful to ensure that the client acknowledges receipt of
1438   the packet(s) containing the response, before the server closes the
1439   input connection. If the client continues sending data to the server
1440   after the close, the server's TCP stack will send a reset packet to
1441   the client, which may erase the client's unacknowledged input buffers
1442   before they can be read and interpreted by the HTTP application.
1445<section title="400 Bad Request" anchor="status.400">
1446  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1447  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1449   The request could not be understood by the server due to malformed
1450   syntax. The client &SHOULD-NOT;  repeat the request without
1451   modifications.
1455<section title="401 Unauthorized" anchor="status.401">
1456  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1457  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1459   The request requires user authentication (see &auth;).
1463<section title="402 Payment Required" anchor="status.402">
1464  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1467   This code is reserved for future use.
1471<section title="403 Forbidden" anchor="status.403">
1472  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1473  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1475   The server understood the request, but is refusing to fulfill it.
1476   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1477   If the request method was not HEAD and the server wishes to make
1478   public why the request has not been fulfilled, it &SHOULD; describe the
1479   reason for the refusal in the entity.  If the server does not wish to
1480   make this information available to the client, the status code 404
1481   (Not Found) can be used instead.
1485<section title="404 Not Found" anchor="status.404">
1486  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1487  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1489   The server has not found anything matching the request-target. No
1490   indication is given of whether the condition is temporary or
1491   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1492   knows, through some internally configurable mechanism, that an old
1493   resource is permanently unavailable and has no forwarding address.
1494   This status code is commonly used when the server does not wish to
1495   reveal exactly why the request has been refused, or when no other
1496   response is applicable.
1500<section title="405 Method Not Allowed" anchor="status.405">
1501  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1502  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1504   The method specified in the Request-Line is not allowed for the
1505   resource identified by the request-target. The response &MUST; include an
1506   Allow header containing a list of valid methods for the requested
1507   resource.
1511<section title="406 Not Acceptable" anchor="status.406">
1512  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1513  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1515   The resource identified by the request is only capable of generating
1516   response entities which have content characteristics not acceptable
1517   according to the accept headers sent in the request.
1520   Unless it was a HEAD request, the response &SHOULD; include an entity
1521   containing a list of available entity characteristics and location(s)
1522   from which the user or user agent can choose the one most
1523   appropriate. The entity format is specified by the media type given
1524   in the Content-Type header field. Depending upon the format and the
1525   capabilities of the user agent, selection of the most appropriate
1526   choice &MAY; be performed automatically. However, this specification
1527   does not define any standard for such automatic selection.
1528  <list><t>
1529      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1530      not acceptable according to the accept headers sent in the
1531      request. In some cases, this may even be preferable to sending a
1532      406 response. User agents are encouraged to inspect the headers of
1533      an incoming response to determine if it is acceptable.
1534  </t></list>
1537   If the response could be unacceptable, a user agent &SHOULD;
1538   temporarily stop receipt of more data and query the user for a
1539   decision on further actions.
1543<section title="407 Proxy Authentication Required" anchor="status.407">
1544  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1545  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1547   This code is similar to 401 (Unauthorized), but indicates that the
1548   client must first authenticate itself with the proxy (see &auth;).
1552<section title="408 Request Timeout" anchor="status.408">
1553  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1554  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1556   The client did not produce a request within the time that the server
1557   was prepared to wait. The client &MAY; repeat the request without
1558   modifications at any later time.
1562<section title="409 Conflict" anchor="status.409">
1563  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1564  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1566   The request could not be completed due to a conflict with the current
1567   state of the resource. This code is only allowed in situations where
1568   it is expected that the user might be able to resolve the conflict
1569   and resubmit the request. The response body &SHOULD; include enough
1570   information for the user to recognize the source of the conflict.
1571   Ideally, the response entity would include enough information for the
1572   user or user agent to fix the problem; however, that might not be
1573   possible and is not required.
1576   Conflicts are most likely to occur in response to a PUT request. For
1577   example, if versioning were being used and the entity being PUT
1578   included changes to a resource which conflict with those made by an
1579   earlier (third-party) request, the server might use the 409 response
1580   to indicate that it can't complete the request. In this case, the
1581   response entity would likely contain a list of the differences
1582   between the two versions in a format defined by the response
1583   Content-Type.
1587<section title="410 Gone" anchor="status.410">
1588  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1589  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1591   The requested resource is no longer available at the server and no
1592   forwarding address is known. This condition is expected to be
1593   considered permanent. Clients with link editing capabilities &SHOULD;
1594   delete references to the request-target after user approval. If the
1595   server does not know, or has no facility to determine, whether or not
1596   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1597   used instead. This response is cacheable unless indicated otherwise.
1600   The 410 response is primarily intended to assist the task of web
1601   maintenance by notifying the recipient that the resource is
1602   intentionally unavailable and that the server owners desire that
1603   remote links to that resource be removed. Such an event is common for
1604   limited-time, promotional services and for resources belonging to
1605   individuals no longer working at the server's site. It is not
1606   necessary to mark all permanently unavailable resources as "gone" or
1607   to keep the mark for any length of time -- that is left to the
1608   discretion of the server owner.
1612<section title="411 Length Required" anchor="status.411">
1613  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1614  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1616   The server refuses to accept the request without a defined Content-Length.
1617   The client &MAY; repeat the request if it adds a valid
1618   Content-Length header field containing the length of the message-body
1619   in the request message.
1623<section title="412 Precondition Failed" anchor="status.412">
1624  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1625  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1627   The precondition given in one or more of the request-header fields
1628   evaluated to false when it was tested on the server, as defined in
1629   &conditional;.
1633<section title="413 Request Entity Too Large" anchor="status.413">
1634  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1635  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1637   The server is refusing to process a request because the request
1638   entity is larger than the server is willing or able to process. The
1639   server &MAY; close the connection to prevent the client from continuing
1640   the request.
1643   If the condition is temporary, the server &SHOULD; include a Retry-After
1644   header field to indicate that it is temporary and after what
1645   time the client &MAY; try again.
1649<section title="414 Request-target Too Long" anchor="status.414">
1650  <iref primary="true" item="414 Request-target Too Long (status code)" x:for-anchor=""/>
1651  <iref primary="true" item="Status Codes" subitem="414 Request-target Too Long" x:for-anchor=""/>
1653   The server is refusing to service the request because the request-target
1654   is longer than the server is willing to interpret. This rare
1655   condition is only likely to occur when a client has improperly
1656   converted a POST request to a GET request with long query
1657   information, when the client has descended into a URI "black hole" of
1658   redirection (e.g., a redirected URI prefix that points to a suffix of
1659   itself), or when the server is under attack by a client attempting to
1660   exploit security holes present in some servers using fixed-length
1661   buffers for reading or manipulating the request-target.
1665<section title="415 Unsupported Media Type" anchor="status.415">
1666  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1667  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1669   The server is refusing to service the request because the entity of
1670   the request is in a format not supported by the requested resource
1671   for the requested method.
1675<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1676  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1677  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1679   The request included a Range request-header field (&header-range;) and none of
1680   the range-specifier values in this field overlap the current extent
1681   of the selected resource.
1685<section title="417 Expectation Failed" anchor="status.417">
1686  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1687  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1689   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1690   could not be met by this server, or, if the server is a proxy,
1691   the server has unambiguous evidence that the request could not be met
1692   by the next-hop server.
1697<section title="Server Error 5xx" anchor="status.5xx">
1699   Response status codes beginning with the digit "5" indicate cases in
1700   which the server is aware that it has erred or is incapable of
1701   performing the request. Except when responding to a HEAD request, the
1702   server &SHOULD; include an entity containing an explanation of the
1703   error situation, and whether it is a temporary or permanent
1704   condition. User agents &SHOULD; display any included entity to the
1705   user. These response codes are applicable to any request method.
1708<section title="500 Internal Server Error" anchor="status.500">
1709  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1710  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1712   The server encountered an unexpected condition which prevented it
1713   from fulfilling the request.
1717<section title="501 Not Implemented" anchor="status.501">
1718  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1719  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1721   The server does not support the functionality required to fulfill the
1722   request. This is the appropriate response when the server does not
1723   recognize the request method and is not capable of supporting it for
1724   any resource.
1728<section title="502 Bad Gateway" anchor="status.502">
1729  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1730  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1732   The server, while acting as a gateway or proxy, received an invalid
1733   response from the upstream server it accessed in attempting to
1734   fulfill the request.
1738<section title="503 Service Unavailable" anchor="status.503">
1739  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1740  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1742   The server is currently unable to handle the request due to a
1743   temporary overloading or maintenance of the server. The implication
1744   is that this is a temporary condition which will be alleviated after
1745   some delay. If known, the length of the delay &MAY; be indicated in a
1746   Retry-After header. If no Retry-After is given, the client &SHOULD;
1747   handle the response as it would for a 500 response.
1748  <list><t>
1749      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1750      server must use it when becoming overloaded. Some servers may wish
1751      to simply refuse the connection.
1752  </t></list>
1756<section title="504 Gateway Timeout" anchor="status.504">
1757  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1760   The server, while acting as a gateway or proxy, did not receive a
1761   timely response from the upstream server specified by the URI (e.g.
1762   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1763   to access in attempting to complete the request.
1764  <list><t>
1765      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1766      return 400 or 500 when DNS lookups time out.
1767  </t></list>
1771<section title="505 HTTP Version Not Supported" anchor="status.505">
1772  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1773  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1775   The server does not support, or refuses to support, the protocol
1776   version that was used in the request message. The server is
1777   indicating that it is unable or unwilling to complete the request
1778   using the same major version as the client, as described in &http-version;,
1779   other than with this error message. The response &SHOULD; contain
1780   an entity describing why that version is not supported and what other
1781   protocols are supported by that server.
1789<section title="Header Field Definitions" anchor="header.fields">
1791   This section defines the syntax and semantics of HTTP/1.1 header fields
1792   related to request and response semantics.
1795   For entity-header fields, both sender and recipient refer to either the
1796   client or the server, depending on who sends and who receives the entity.
1799<section title="Allow" anchor="header.allow">
1800  <iref primary="true" item="Allow header" x:for-anchor=""/>
1801  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1802  <x:anchor-alias value="Allow"/>
1803  <x:anchor-alias value="Allow-v"/>
1805      The response-header field "Allow" lists the set of methods advertised as
1806      supported by the resource identified by the request-target. The purpose of
1807      this field is strictly to inform the recipient of valid methods
1808      associated with the resource. An Allow header field &MUST; be
1809      present in a 405 (Method Not Allowed) response.
1811<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1812  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1813  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1816      Example of use:
1818<figure><artwork type="example">
1819  Allow: GET, HEAD, PUT
1822      The actual set of allowed methods is defined
1823      by the origin server at the time of each request.
1826      A proxy &MUST-NOT; modify the Allow header field even if it does not
1827      understand all the methods specified, since the user agent might
1828      have other means of communicating with the origin server.
1832<section title="Expect" anchor="header.expect">
1833  <iref primary="true" item="Expect header" x:for-anchor=""/>
1834  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1835  <x:anchor-alias value="Expect"/>
1836  <x:anchor-alias value="Expect-v"/>
1837  <x:anchor-alias value="expectation"/>
1838  <x:anchor-alias value="expectation-extension"/>
1839  <x:anchor-alias value="expect-params"/>
1841   The request-header field "Expect" is used to indicate that particular
1842   server behaviors are required by the client.
1844<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"/>
1845  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1846  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1848  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1849  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1850                           *<x:ref>expect-params</x:ref> ]
1851  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1854   A server that does not understand or is unable to comply with any of
1855   the expectation values in the Expect field of a request &MUST; respond
1856   with appropriate error status. The server &MUST; respond with a 417
1857   (Expectation Failed) status if any of the expectations cannot be met
1858   or, if there are other problems with the request, some other 4xx
1859   status.
1862   This header field is defined with extensible syntax to allow for
1863   future extensions. If a server receives a request containing an
1864   Expect field that includes an expectation-extension that it does not
1865   support, it &MUST; respond with a 417 (Expectation Failed) status.
1868   Comparison of expectation values is case-insensitive for unquoted
1869   tokens (including the 100-continue token), and is case-sensitive for
1870   quoted-string expectation-extensions.
1873   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1874   return a 417 (Expectation Failed) status if it receives a request
1875   with an expectation that it cannot meet. However, the Expect
1876   request-header itself is end-to-end; it &MUST; be forwarded if the
1877   request is forwarded.
1880   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1881   Expect header.
1884   See &use100; for the use of the 100 (Continue) status.
1888<section title="From" anchor="header.from">
1889  <iref primary="true" item="From header" x:for-anchor=""/>
1890  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1891  <x:anchor-alias value="From"/>
1892  <x:anchor-alias value="From-v"/>
1893  <x:anchor-alias value="mailbox"/>
1895   The request-header field "From", if given, &SHOULD; contain an Internet
1896   e-mail address for the human user who controls the requesting user
1897   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1898   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1900<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1901  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1902  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1904  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1907   An example is:
1909<figure><artwork type="example">
1910  From:
1913   This header field &MAY; be used for logging purposes and as a means for
1914   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1915   be used as an insecure form of access protection. The interpretation
1916   of this field is that the request is being performed on behalf of the
1917   person given, who accepts responsibility for the method performed. In
1918   particular, robot agents &SHOULD; include this header so that the
1919   person responsible for running the robot can be contacted if problems
1920   occur on the receiving end.
1923   The Internet e-mail address in this field &MAY; be separate from the
1924   Internet host which issued the request. For example, when a request
1925   is passed through a proxy the original issuer's address &SHOULD; be
1926   used.
1929   The client &SHOULD-NOT;  send the From header field without the user's
1930   approval, as it might conflict with the user's privacy interests or
1931   their site's security policy. It is strongly recommended that the
1932   user be able to disable, enable, and modify the value of this field
1933   at any time prior to a request.
1937<section title="Location" anchor="header.location">
1938  <iref primary="true" item="Location header" x:for-anchor=""/>
1939  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1940  <x:anchor-alias value="Location"/>
1941  <x:anchor-alias value="Location-v"/>
1943   The response-header field "Location" is used for the identification of a
1944   new resource or to redirect the recipient to a location other than the
1945   request-target for completion of the request.  For 201 (Created)
1946   responses, the Location is that of the new resource which was created
1947   by the request. For 3xx responses, the location &SHOULD; indicate the
1948   server's preferred URI for automatic redirection to the resource. The
1949   field value consists of a single absolute URI.
1951<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1952  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1953  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1956   An example is:
1958<figure><artwork type="example">
1959  Location:
1962  <list><t>
1963      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1964      from Location in that the Content-Location identifies the original
1965      location of the entity enclosed in the response. It is therefore
1966      possible for a response to contain header fields for both Location
1967      and Content-Location.
1968  </t></list>
1971   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1972   <list style="symbols">
1973      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1974      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1975      <t>With 305 Use Proxy.</t>
1976   </list>
1980<section title="Max-Forwards" anchor="header.max-forwards">
1981  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1982  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1983  <x:anchor-alias value="Max-Forwards"/>
1984  <x:anchor-alias value="Max-Forwards-v"/>
1986   The request-header "Max-Forwards" field provides a mechanism with the
1987   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1988   number of proxies or gateways that can forward the request to the
1989   next inbound server. This can be useful when the client is attempting
1990   to trace a request chain which appears to be failing or looping in
1991   mid-chain.
1993<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
1994  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
1995  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
1998   The Max-Forwards value is a decimal integer indicating the remaining
1999   number of times this request message may be forwarded.
2002   Each proxy or gateway recipient of a TRACE or OPTIONS request
2003   containing a Max-Forwards header field &MUST; check and update its
2004   value prior to forwarding the request. If the received value is zero
2005   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2006   respond as the final recipient. If the received Max-Forwards value is
2007   greater than zero, then the forwarded message &MUST; contain an updated
2008   Max-Forwards field with a value decremented by one (1).
2011   The Max-Forwards header field &MAY; be ignored for all other methods
2012   defined by this specification and for any extension methods for which
2013   it is not explicitly referred to as part of that method definition.
2017<section title="Referer" anchor="header.referer">
2018  <iref primary="true" item="Referer header" x:for-anchor=""/>
2019  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2020  <x:anchor-alias value="Referer"/>
2021  <x:anchor-alias value="Referer-v"/>
2023   The request-header field "Referer" [sic] allows the client to specify,
2024   for the server's benefit, the address (URI) of the resource from
2025   which the request-target was obtained (the "referrer", although the
2026   header field is misspelled.) The Referer request-header allows a
2027   server to generate lists of back-links to resources for interest,
2028   logging, optimized caching, etc. It also allows obsolete or mistyped
2029   links to be traced for maintenance. The Referer field &MUST-NOT; be
2030   sent if the request-target was obtained from a source that does not have
2031   its own URI, such as input from the user keyboard.
2033<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2034  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2035  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2038   Example:
2040<figure><artwork type="example">
2041  Referer:
2044   If the field value is a relative URI, it &SHOULD; be interpreted
2045   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2046   <xref target=""/> for security considerations.
2050<section title="Retry-After" anchor="header.retry-after">
2051  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2052  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2053  <x:anchor-alias value="Retry-After"/>
2054  <x:anchor-alias value="Retry-After-v"/>
2056   The response-header "Retry-After" field can be used with a 503 (Service
2057   Unavailable) response to indicate how long the service is expected to
2058   be unavailable to the requesting client. This field &MAY; also be used
2059   with any 3xx (Redirection) response to indicate the minimum time the
2060   user-agent is asked wait before issuing the redirected request. The
2061   value of this field can be either an HTTP-date or an integer number
2062   of seconds (in decimal) after the time of the response.
2064<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2065  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2066  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2068<t anchor="">
2069  <x:anchor-alias value="delta-seconds"/>
2070   Time spans are non-negative decimal integers, representing time in
2071   seconds.
2073<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2074  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2077   Two examples of its use are
2079<figure><artwork type="example">
2080  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2081  Retry-After: 120
2084   In the latter example, the delay is 2 minutes.
2088<section title="Server" anchor="header.server">
2089  <iref primary="true" item="Server header" x:for-anchor=""/>
2090  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2091  <x:anchor-alias value="Server"/>
2092  <x:anchor-alias value="Server-v"/>
2094   The response-header field "Server" contains information about the
2095   software used by the origin server to handle the request. The field
2096   can contain multiple product tokens (&product-tokens;) and comments
2097   identifying the server and any significant subproducts. The product
2098   tokens are listed in order of their significance for identifying the
2099   application.
2101<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2102  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2103  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2104                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2107   Example:
2109<figure><artwork type="example">
2110  Server: CERN/3.0 libwww/2.17
2113   If the response is being forwarded through a proxy, the proxy
2114   application &MUST-NOT; modify the Server response-header. Instead, it
2115   &MUST; include a Via field (as described in &header-via;).
2116  <list><t>
2117      <x:h>Note:</x:h> Revealing the specific software version of the server might
2118      allow the server machine to become more vulnerable to attacks
2119      against software that is known to contain security holes. Server
2120      implementors are encouraged to make this field a configurable
2121      option.
2122  </t></list>
2126<section title="User-Agent" anchor="header.user-agent">
2127  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2128  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2129  <x:anchor-alias value="User-Agent"/>
2130  <x:anchor-alias value="User-Agent-v"/>
2132   The request-header field "User-Agent" contains information about the
2133   user agent originating the request. This is for statistical purposes,
2134   the tracing of protocol violations, and automated recognition of user
2135   agents for the sake of tailoring responses to avoid particular user
2136   agent limitations. User agents &SHOULD; include this field with
2137   requests. The field can contain multiple product tokens (&product-tokens;)
2138   and comments identifying the agent and any subproducts which form a
2139   significant part of the user agent. By convention, the product tokens
2140   are listed in order of their significance for identifying the
2141   application.
2143<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2144  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2145  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2146                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2149   Example:
2151<figure><artwork type="example">
2152  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2158<section title="IANA Considerations" anchor="IANA.considerations">
2160<section title="Method Registry" anchor="method.registration">
2162  The registration procedure for HTTP Methods is defined by
2163  <xref target="method.registry"/> of this document.
2166   The HTTP Method Registry located at <eref target=""/>
2167   should be populated with the registrations below:
2169<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2170<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2171   <ttcol>Method</ttcol>
2172   <ttcol>Safe</ttcol>
2173   <ttcol>Reference</ttcol>
2174   <c>CONNECT</c>
2175   <c>no</c>
2176   <c>
2177      <xref target="CONNECT"/>
2178   </c>
2179   <c>DELETE</c>
2180   <c>no</c>
2181   <c>
2182      <xref target="DELETE"/>
2183   </c>
2184   <c>GET</c>
2185   <c>yes</c>
2186   <c>
2187      <xref target="GET"/>
2188   </c>
2189   <c>HEAD</c>
2190   <c>yes</c>
2191   <c>
2192      <xref target="HEAD"/>
2193   </c>
2194   <c>OPTIONS</c>
2195   <c>yes</c>
2196   <c>
2197      <xref target="OPTIONS"/>
2198   </c>
2199   <c>POST</c>
2200   <c>no</c>
2201   <c>
2202      <xref target="POST"/>
2203   </c>
2204   <c>PUT</c>
2205   <c>no</c>
2206   <c>
2207      <xref target="PUT"/>
2208   </c>
2209   <c>TRACE</c>
2210   <c>yes</c>
2211   <c>
2212      <xref target="TRACE"/>
2213   </c>
2218<section title="Status Code Registry" anchor="status.code.registration">
2220   The registration procedure for HTTP Status Codes -- previously defined
2221   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2222   by <xref target="status.code.registry"/> of this document.
2225   The HTTP Status Code Registry located at <eref target=""/>
2226   should be updated with the registrations below:
2228<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2229<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2230   <ttcol>Value</ttcol>
2231   <ttcol>Description</ttcol>
2232   <ttcol>Reference</ttcol>
2233   <c>100</c>
2234   <c>Continue</c>
2235   <c>
2236      <xref target="status.100"/>
2237   </c>
2238   <c>101</c>
2239   <c>Switching Protocols</c>
2240   <c>
2241      <xref target="status.101"/>
2242   </c>
2243   <c>200</c>
2244   <c>OK</c>
2245   <c>
2246      <xref target="status.200"/>
2247   </c>
2248   <c>201</c>
2249   <c>Created</c>
2250   <c>
2251      <xref target="status.201"/>
2252   </c>
2253   <c>202</c>
2254   <c>Accepted</c>
2255   <c>
2256      <xref target="status.202"/>
2257   </c>
2258   <c>203</c>
2259   <c>Non-Authoritative Information</c>
2260   <c>
2261      <xref target="status.203"/>
2262   </c>
2263   <c>204</c>
2264   <c>No Content</c>
2265   <c>
2266      <xref target="status.204"/>
2267   </c>
2268   <c>205</c>
2269   <c>Reset Content</c>
2270   <c>
2271      <xref target="status.205"/>
2272   </c>
2273   <c>206</c>
2274   <c>Partial Content</c>
2275   <c>
2276      <xref target="status.206"/>
2277   </c>
2278   <c>300</c>
2279   <c>Multiple Choices</c>
2280   <c>
2281      <xref target="status.300"/>
2282   </c>
2283   <c>301</c>
2284   <c>Moved Permanently</c>
2285   <c>
2286      <xref target="status.301"/>
2287   </c>
2288   <c>302</c>
2289   <c>Found</c>
2290   <c>
2291      <xref target="status.302"/>
2292   </c>
2293   <c>303</c>
2294   <c>See Other</c>
2295   <c>
2296      <xref target="status.303"/>
2297   </c>
2298   <c>304</c>
2299   <c>Not Modified</c>
2300   <c>
2301      <xref target="status.304"/>
2302   </c>
2303   <c>305</c>
2304   <c>Use Proxy</c>
2305   <c>
2306      <xref target="status.305"/>
2307   </c>
2308   <c>306</c>
2309   <c>(Unused)</c>
2310   <c>
2311      <xref target="status.306"/>
2312   </c>
2313   <c>307</c>
2314   <c>Temporary Redirect</c>
2315   <c>
2316      <xref target="status.307"/>
2317   </c>
2318   <c>400</c>
2319   <c>Bad Request</c>
2320   <c>
2321      <xref target="status.400"/>
2322   </c>
2323   <c>401</c>
2324   <c>Unauthorized</c>
2325   <c>
2326      <xref target="status.401"/>
2327   </c>
2328   <c>402</c>
2329   <c>Payment Required</c>
2330   <c>
2331      <xref target="status.402"/>
2332   </c>
2333   <c>403</c>
2334   <c>Forbidden</c>
2335   <c>
2336      <xref target="status.403"/>
2337   </c>
2338   <c>404</c>
2339   <c>Not Found</c>
2340   <c>
2341      <xref target="status.404"/>
2342   </c>
2343   <c>405</c>
2344   <c>Method Not Allowed</c>
2345   <c>
2346      <xref target="status.405"/>
2347   </c>
2348   <c>406</c>
2349   <c>Not Acceptable</c>
2350   <c>
2351      <xref target="status.406"/>
2352   </c>
2353   <c>407</c>
2354   <c>Proxy Authentication Required</c>
2355   <c>
2356      <xref target="status.407"/>
2357   </c>
2358   <c>408</c>
2359   <c>Request Timeout</c>
2360   <c>
2361      <xref target="status.408"/>
2362   </c>
2363   <c>409</c>
2364   <c>Conflict</c>
2365   <c>
2366      <xref target="status.409"/>
2367   </c>
2368   <c>410</c>
2369   <c>Gone</c>
2370   <c>
2371      <xref target="status.410"/>
2372   </c>
2373   <c>411</c>
2374   <c>Length Required</c>
2375   <c>
2376      <xref target="status.411"/>
2377   </c>
2378   <c>412</c>
2379   <c>Precondition Failed</c>
2380   <c>
2381      <xref target="status.412"/>
2382   </c>
2383   <c>413</c>
2384   <c>Request Entity Too Large</c>
2385   <c>
2386      <xref target="status.413"/>
2387   </c>
2388   <c>414</c>
2389   <c>Request-target Too Long</c>
2390   <c>
2391      <xref target="status.414"/>
2392   </c>
2393   <c>415</c>
2394   <c>Unsupported Media Type</c>
2395   <c>
2396      <xref target="status.415"/>
2397   </c>
2398   <c>416</c>
2399   <c>Requested Range Not Satisfiable</c>
2400   <c>
2401      <xref target="status.416"/>
2402   </c>
2403   <c>417</c>
2404   <c>Expectation Failed</c>
2405   <c>
2406      <xref target="status.417"/>
2407   </c>
2408   <c>500</c>
2409   <c>Internal Server Error</c>
2410   <c>
2411      <xref target="status.500"/>
2412   </c>
2413   <c>501</c>
2414   <c>Not Implemented</c>
2415   <c>
2416      <xref target="status.501"/>
2417   </c>
2418   <c>502</c>
2419   <c>Bad Gateway</c>
2420   <c>
2421      <xref target="status.502"/>
2422   </c>
2423   <c>503</c>
2424   <c>Service Unavailable</c>
2425   <c>
2426      <xref target="status.503"/>
2427   </c>
2428   <c>504</c>
2429   <c>Gateway Timeout</c>
2430   <c>
2431      <xref target="status.504"/>
2432   </c>
2433   <c>505</c>
2434   <c>HTTP Version Not Supported</c>
2435   <c>
2436      <xref target="status.505"/>
2437   </c>
2441<section title="Message Header Registration" anchor="message.header.registration">
2443   The Message Header Registry located at <eref target=""/> should be updated
2444   with the permanent registrations below (see <xref target="RFC3864"/>):
2446<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2447<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2448   <ttcol>Header Field Name</ttcol>
2449   <ttcol>Protocol</ttcol>
2450   <ttcol>Status</ttcol>
2451   <ttcol>Reference</ttcol>
2452   <c>Allow</c>
2453   <c>http</c>
2454   <c>standard</c>
2455   <c>
2456      <xref target="header.allow"/>
2457   </c>
2458   <c>Expect</c>
2459   <c>http</c>
2460   <c>standard</c>
2461   <c>
2462      <xref target="header.expect"/>
2463   </c>
2464   <c>From</c>
2465   <c>http</c>
2466   <c>standard</c>
2467   <c>
2468      <xref target="header.from"/>
2469   </c>
2470   <c>Location</c>
2471   <c>http</c>
2472   <c>standard</c>
2473   <c>
2474      <xref target="header.location"/>
2475   </c>
2476   <c>Max-Forwards</c>
2477   <c>http</c>
2478   <c>standard</c>
2479   <c>
2480      <xref target="header.max-forwards"/>
2481   </c>
2482   <c>Referer</c>
2483   <c>http</c>
2484   <c>standard</c>
2485   <c>
2486      <xref target="header.referer"/>
2487   </c>
2488   <c>Retry-After</c>
2489   <c>http</c>
2490   <c>standard</c>
2491   <c>
2492      <xref target="header.retry-after"/>
2493   </c>
2494   <c>Server</c>
2495   <c>http</c>
2496   <c>standard</c>
2497   <c>
2498      <xref target="header.server"/>
2499   </c>
2500   <c>User-Agent</c>
2501   <c>http</c>
2502   <c>standard</c>
2503   <c>
2504      <xref target="header.user-agent"/>
2505   </c>
2509   The change controller is: "IETF ( - Internet Engineering Task Force".
2514<section title="Security Considerations" anchor="security.considerations">
2516   This section is meant to inform application developers, information
2517   providers, and users of the security limitations in HTTP/1.1 as
2518   described by this document. The discussion does not include
2519   definitive solutions to the problems revealed, though it does make
2520   some suggestions for reducing security risks.
2523<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2525   Like any generic data transfer protocol, HTTP cannot regulate the
2526   content of the data that is transferred, nor is there any a priori
2527   method of determining the sensitivity of any particular piece of
2528   information within the context of any given request. Therefore,
2529   applications &SHOULD; supply as much control over this information as
2530   possible to the provider of that information. Four header fields are
2531   worth special mention in this context: Server, Via, Referer and From.
2534   Revealing the specific software version of the server might allow the
2535   server machine to become more vulnerable to attacks against software
2536   that is known to contain security holes. Implementors &SHOULD; make the
2537   Server header field a configurable option.
2540   Proxies which serve as a portal through a network firewall &SHOULD;
2541   take special precautions regarding the transfer of header information
2542   that identifies the hosts behind the firewall. In particular, they
2543   &SHOULD; remove, or replace with sanitized versions, any Via fields
2544   generated behind the firewall.
2547   The Referer header allows reading patterns to be studied and reverse
2548   links drawn. Although it can be very useful, its power can be abused
2549   if user details are not separated from the information contained in
2550   the Referer. Even when the personal information has been removed, the
2551   Referer header might indicate a private document's URI whose
2552   publication would be inappropriate.
2555   The information sent in the From field might conflict with the user's
2556   privacy interests or their site's security policy, and hence it
2557   &SHOULD-NOT;  be transmitted without the user being able to disable,
2558   enable, and modify the contents of the field. The user &MUST; be able
2559   to set the contents of this field within a user preference or
2560   application defaults configuration.
2563   We suggest, though do not require, that a convenient toggle interface
2564   be provided for the user to enable or disable the sending of From and
2565   Referer information.
2568   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2569   fields can sometimes be used to determine that a specific client or
2570   server have a particular security hole which might be exploited.
2571   Unfortunately, this same information is often used for other valuable
2572   purposes for which HTTP currently has no better mechanism.
2576<section title="Encoding Sensitive Information in URIs" anchor="">
2578   Because the source of a link might be private information or might
2579   reveal an otherwise private information source, it is strongly
2580   recommended that the user be able to select whether or not the
2581   Referer field is sent. For example, a browser client could have a
2582   toggle switch for browsing openly/anonymously, which would
2583   respectively enable/disable the sending of Referer and From
2584   information.
2587   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2588   HTTP request if the referring page was transferred with a secure
2589   protocol.
2592   Authors of services should not use
2593   GET-based forms for the submission of sensitive data because that
2594   data will be encoded in the Request-target. Many existing
2595   servers, proxies, and user agents log or display the Request-target in
2596   places where it might be visible to third parties. Such services can
2597   use POST-based form submission instead.
2601<section title="Location Headers and Spoofing" anchor="location.spoofing">
2603   If a single server supports multiple organizations that do not trust
2604   one another, then it &MUST; check the values of Location and Content-Location
2605   headers in responses that are generated under control of
2606   said organizations to make sure that they do not attempt to
2607   invalidate resources over which they have no authority.
2613<section title="Acknowledgments" anchor="ack">
2618<references title="Normative References">
2620<reference anchor="Part1">
2621  <front>
2622    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2623    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2624      <organization abbrev="Day Software">Day Software</organization>
2625      <address><email></email></address>
2626    </author>
2627    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2628      <organization>One Laptop per Child</organization>
2629      <address><email></email></address>
2630    </author>
2631    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2632      <organization abbrev="HP">Hewlett-Packard Company</organization>
2633      <address><email></email></address>
2634    </author>
2635    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2636      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2637      <address><email></email></address>
2638    </author>
2639    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2640      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2641      <address><email></email></address>
2642    </author>
2643    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2644      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2645      <address><email></email></address>
2646    </author>
2647    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2648      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2649      <address><email></email></address>
2650    </author>
2651    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2652      <organization abbrev="W3C">World Wide Web Consortium</organization>
2653      <address><email></email></address>
2654    </author>
2655    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2656      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2657      <address><email></email></address>
2658    </author>
2659    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2660  </front>
2661  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2662  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2665<reference anchor="Part3">
2666  <front>
2667    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2668    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2669      <organization abbrev="Day Software">Day Software</organization>
2670      <address><email></email></address>
2671    </author>
2672    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2673      <organization>One Laptop per Child</organization>
2674      <address><email></email></address>
2675    </author>
2676    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2677      <organization abbrev="HP">Hewlett-Packard Company</organization>
2678      <address><email></email></address>
2679    </author>
2680    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2681      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2682      <address><email></email></address>
2683    </author>
2684    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2685      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2686      <address><email></email></address>
2687    </author>
2688    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2689      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2690      <address><email></email></address>
2691    </author>
2692    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2693      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2694      <address><email></email></address>
2695    </author>
2696    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2697      <organization abbrev="W3C">World Wide Web Consortium</organization>
2698      <address><email></email></address>
2699    </author>
2700    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2701      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2702      <address><email></email></address>
2703    </author>
2704    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2705  </front>
2706  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2707  <x:source href="p3-payload.xml" basename="p3-payload"/>
2710<reference anchor="Part4">
2711  <front>
2712    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2713    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2714      <organization abbrev="Day Software">Day Software</organization>
2715      <address><email></email></address>
2716    </author>
2717    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2718      <organization>One Laptop per Child</organization>
2719      <address><email></email></address>
2720    </author>
2721    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2722      <organization abbrev="HP">Hewlett-Packard Company</organization>
2723      <address><email></email></address>
2724    </author>
2725    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2726      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2727      <address><email></email></address>
2728    </author>
2729    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2730      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2731      <address><email></email></address>
2732    </author>
2733    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2734      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2735      <address><email></email></address>
2736    </author>
2737    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2738      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2739      <address><email></email></address>
2740    </author>
2741    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2742      <organization abbrev="W3C">World Wide Web Consortium</organization>
2743      <address><email></email></address>
2744    </author>
2745    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2746      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2747      <address><email></email></address>
2748    </author>
2749    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2750  </front>
2751  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2752  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2755<reference anchor="Part5">
2756  <front>
2757    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2758    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2759      <organization abbrev="Day Software">Day Software</organization>
2760      <address><email></email></address>
2761    </author>
2762    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2763      <organization>One Laptop per Child</organization>
2764      <address><email></email></address>
2765    </author>
2766    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2767      <organization abbrev="HP">Hewlett-Packard Company</organization>
2768      <address><email></email></address>
2769    </author>
2770    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2771      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2772      <address><email></email></address>
2773    </author>
2774    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2775      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2776      <address><email></email></address>
2777    </author>
2778    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2779      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2780      <address><email></email></address>
2781    </author>
2782    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2783      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2784      <address><email></email></address>
2785    </author>
2786    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2787      <organization abbrev="W3C">World Wide Web Consortium</organization>
2788      <address><email></email></address>
2789    </author>
2790    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2791      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2792      <address><email></email></address>
2793    </author>
2794    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2795  </front>
2796  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2797  <x:source href="p5-range.xml" basename="p5-range"/>
2800<reference anchor="Part6">
2801  <front>
2802    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2803    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2804      <organization abbrev="Day Software">Day Software</organization>
2805      <address><email></email></address>
2806    </author>
2807    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2808      <organization>One Laptop per Child</organization>
2809      <address><email></email></address>
2810    </author>
2811    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2812      <organization abbrev="HP">Hewlett-Packard Company</organization>
2813      <address><email></email></address>
2814    </author>
2815    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2816      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2817      <address><email></email></address>
2818    </author>
2819    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2820      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2821      <address><email></email></address>
2822    </author>
2823    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2824      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2825      <address><email></email></address>
2826    </author>
2827    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2828      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2829      <address><email></email></address>
2830    </author>
2831    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2832      <organization abbrev="W3C">World Wide Web Consortium</organization>
2833      <address><email></email></address>
2834    </author>
2835    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2836      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2837      <address><email></email></address>
2838    </author>
2839    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2840  </front>
2841  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2842  <x:source href="p6-cache.xml" basename="p6-cache"/>
2845<reference anchor="Part7">
2846  <front>
2847    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2848    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2849      <organization abbrev="Day Software">Day Software</organization>
2850      <address><email></email></address>
2851    </author>
2852    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2853      <organization>One Laptop per Child</organization>
2854      <address><email></email></address>
2855    </author>
2856    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2857      <organization abbrev="HP">Hewlett-Packard Company</organization>
2858      <address><email></email></address>
2859    </author>
2860    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2861      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2862      <address><email></email></address>
2863    </author>
2864    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2865      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2866      <address><email></email></address>
2867    </author>
2868    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2869      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2870      <address><email></email></address>
2871    </author>
2872    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2873      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2874      <address><email></email></address>
2875    </author>
2876    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2877      <organization abbrev="W3C">World Wide Web Consortium</organization>
2878      <address><email></email></address>
2879    </author>
2880    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2881      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2882      <address><email></email></address>
2883    </author>
2884    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2885  </front>
2886  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2887  <x:source href="p7-auth.xml" basename="p7-auth"/>
2890<reference anchor="RFC2119">
2891  <front>
2892    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2893    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2894      <organization>Harvard University</organization>
2895      <address><email></email></address>
2896    </author>
2897    <date month="March" year="1997"/>
2898  </front>
2899  <seriesInfo name="BCP" value="14"/>
2900  <seriesInfo name="RFC" value="2119"/>
2905<references title="Informative References">
2907<reference anchor="RFC1945">
2908  <front>
2909    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2910    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2911      <organization>MIT, Laboratory for Computer Science</organization>
2912      <address><email></email></address>
2913    </author>
2914    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2915      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2916      <address><email></email></address>
2917    </author>
2918    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2919      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2920      <address><email></email></address>
2921    </author>
2922    <date month="May" year="1996"/>
2923  </front>
2924  <seriesInfo name="RFC" value="1945"/>
2927<reference anchor="RFC2068">
2928  <front>
2929    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2930    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2931      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2932      <address><email></email></address>
2933    </author>
2934    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2935      <organization>MIT Laboratory for Computer Science</organization>
2936      <address><email></email></address>
2937    </author>
2938    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2939      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2940      <address><email></email></address>
2941    </author>
2942    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2943      <organization>MIT Laboratory for Computer Science</organization>
2944      <address><email></email></address>
2945    </author>
2946    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2947      <organization>MIT Laboratory for Computer Science</organization>
2948      <address><email></email></address>
2949    </author>
2950    <date month="January" year="1997"/>
2951  </front>
2952  <seriesInfo name="RFC" value="2068"/>
2955<reference anchor="RFC2616">
2956  <front>
2957    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2958    <author initials="R." surname="Fielding" fullname="R. Fielding">
2959      <organization>University of California, Irvine</organization>
2960      <address><email></email></address>
2961    </author>
2962    <author initials="J." surname="Gettys" fullname="J. Gettys">
2963      <organization>W3C</organization>
2964      <address><email></email></address>
2965    </author>
2966    <author initials="J." surname="Mogul" fullname="J. Mogul">
2967      <organization>Compaq Computer Corporation</organization>
2968      <address><email></email></address>
2969    </author>
2970    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2971      <organization>MIT Laboratory for Computer Science</organization>
2972      <address><email></email></address>
2973    </author>
2974    <author initials="L." surname="Masinter" fullname="L. Masinter">
2975      <organization>Xerox Corporation</organization>
2976      <address><email></email></address>
2977    </author>
2978    <author initials="P." surname="Leach" fullname="P. Leach">
2979      <organization>Microsoft Corporation</organization>
2980      <address><email></email></address>
2981    </author>
2982    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2983      <organization>W3C</organization>
2984      <address><email></email></address>
2985    </author>
2986    <date month="June" year="1999"/>
2987  </front>
2988  <seriesInfo name="RFC" value="2616"/>
2991<reference anchor='RFC2817'>
2992  <front>
2993    <title>Upgrading to TLS Within HTTP/1.1</title>
2994    <author initials='R.' surname='Khare' fullname='R. Khare'>
2995      <organization>4K Associates / UC Irvine</organization>
2996      <address><email></email></address>
2997    </author>
2998    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2999      <organization>Agranat Systems, Inc.</organization>
3000      <address><email></email></address>
3001    </author>
3002    <date year='2000' month='May' />
3003  </front>
3004  <seriesInfo name='RFC' value='2817' />
3007<reference anchor='RFC3864'>
3008  <front>
3009    <title>Registration Procedures for Message Header Fields</title>
3010    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3011      <organization>Nine by Nine</organization>
3012      <address><email></email></address>
3013    </author>
3014    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3015      <organization>BEA Systems</organization>
3016      <address><email></email></address>
3017    </author>
3018    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3019      <organization>HP Labs</organization>
3020      <address><email></email></address>
3021    </author>
3022    <date year='2004' month='September' />
3023  </front>
3024  <seriesInfo name='BCP' value='90' />
3025  <seriesInfo name='RFC' value='3864' />
3028<reference anchor='RFC5226'>
3029  <front>
3030    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3031    <author initials='T.' surname='Narten' fullname='T. Narten'>
3032      <organization>IBM</organization>
3033      <address><email></email></address>
3034    </author>
3035    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3036      <organization>Google</organization>
3037      <address><email></email></address>
3038    </author>
3039    <date year='2008' month='May' />
3040  </front>
3041  <seriesInfo name='BCP' value='26' />
3042  <seriesInfo name='RFC' value='5226' />
3045<reference anchor="RFC5322">
3046  <front>
3047    <title>Internet Message Format</title>
3048    <author initials="P." surname="Resnick" fullname="P. Resnick">
3049      <organization>Qualcomm Incorporated</organization>
3050    </author>
3051    <date year="2008" month="October"/>
3052  </front>
3053  <seriesInfo name="RFC" value="5322"/>
3058<section title="Compatibility with Previous Versions" anchor="compatibility">
3059<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3061   Clarified which error code should be used for inbound server failures
3062   (e.g. DNS failures). (<xref target="status.504"/>).
3065   201 (Created) had a race that required an Etag be sent when a resource is
3066   first created. (<xref target="status.201"/>).
3069   Rewrite of message transmission requirements to make it much harder
3070   for implementors to get it wrong, as the consequences of errors here
3071   can have significant impact on the Internet, and to deal with the
3072   following problems:
3073  <list style="numbers">
3074      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3075         this was incorrectly placing a requirement on the behavior of
3076         an implementation of a future version of HTTP/1.x</t>
3078      <t>Made it clear that user-agents should retry requests, not
3079         "clients" in general.</t>
3081      <t>Converted requirements for clients to ignore unexpected 100
3082         (Continue) responses, and for proxies to forward 100 responses,
3083         into a general requirement for 1xx responses.</t>
3085      <t>Modified some TCP-specific language, to make it clearer that
3086         non-TCP transports are possible for HTTP.</t>
3088      <t>Require that the origin server &MUST-NOT; wait for the request
3089         body before it sends a required 100 (Continue) response.</t>
3091      <t>Allow, rather than require, a server to omit 100 (Continue) if
3092         it has already seen some of the request body.</t>
3094      <t>Allow servers to defend against denial-of-service attacks and
3095         broken clients.</t>
3096  </list>
3099   This change adds the Expect header and 417 status code.
3102   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3103   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3106   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
3107   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3111<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3113  This document takes over the Status Code Registry, previously defined
3114  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3115  (<xref target="status.code.registry"/>)
3118  Clarify definition of POST.
3119  (<xref target="POST"/>)
3122  Failed to consider that there are
3123  many other request methods that are safe to automatically redirect,
3124  and further that the user agent is able to make that determination
3125  based on the request method semantics.
3126  (Sections <xref format="counter" target="status.301"/>,
3127  <xref format="counter" target="status.302"/> and
3128  <xref format="counter" target="status.307"/>)
3131  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3132  It used to indicate that the requested resource must be accessed through the
3133  proxy given by the Location field. The Location field gave the URI of the
3134  proxy. The recipient was expected to repeat this single request via the proxy.
3135  (<xref target="status.305"/>)
3138  Reclassify Allow header as response header, removing the option to
3139  specify it in a PUT request.
3140  Relax the server requirement on the contents of the Allow header and
3141  remove requirement on clients to always trust the header value.
3142  (<xref target="header.allow"/>)
3145  Correct syntax of Location header to allow fragment,
3146  as referred symbol wasn't what was expected, and add some
3147  clarifications as to when it would not be appropriate.
3148  (<xref target="header.location"/>)
3151  In the description of the Server header, the Via field
3152  was described as a SHOULD. The requirement was and is stated
3153  correctly in the description of the Via header in &header-via;.
3154  (<xref target="header.server"/>)
3160<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3162<section title="Since RFC2616">
3164  Extracted relevant partitions from <xref target="RFC2616"/>.
3168<section title="Since draft-ietf-httpbis-p2-semantics-00">
3170  Closed issues:
3171  <list style="symbols">
3172    <t>
3173      <eref target=""/>:
3174      "Via is a MUST"
3175      (<eref target=""/>)
3176    </t>
3177    <t>
3178      <eref target=""/>:
3179      "Fragments allowed in Location"
3180      (<eref target=""/>)
3181    </t>
3182    <t>
3183      <eref target=""/>:
3184      "Safe Methods vs Redirection"
3185      (<eref target=""/>)
3186    </t>
3187    <t>
3188      <eref target=""/>:
3189      "Revise description of the POST method"
3190      (<eref target=""/>)
3191    </t>
3192    <t>
3193      <eref target=""/>:
3194      "Normative and Informative references"
3195    </t>
3196    <t>
3197      <eref target=""/>:
3198      "RFC2606 Compliance"
3199    </t>
3200    <t>
3201      <eref target=""/>:
3202      "Informative references"
3203    </t>
3204    <t>
3205      <eref target=""/>:
3206      "Redundant cross-references"
3207    </t>
3208  </list>
3211  Other changes:
3212  <list style="symbols">
3213    <t>
3214      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3215    </t>
3216  </list>
3220<section title="Since draft-ietf-httpbis-p2-semantics-01">
3222  Closed issues:
3223  <list style="symbols">
3224    <t>
3225      <eref target=""/>:
3226      "PUT side effects"
3227    </t>
3228    <t>
3229      <eref target=""/>:
3230      "Duplicate Host header requirements"
3231    </t>
3232  </list>
3235  Ongoing work on ABNF conversion (<eref target=""/>):
3236  <list style="symbols">
3237    <t>
3238      Move "Product Tokens" section (back) into Part 1, as "token" is used
3239      in the definition of the Upgrade header.
3240    </t>
3241    <t>
3242      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3243    </t>
3244    <t>
3245      Copy definition of delta-seconds from Part6 instead of referencing it.
3246    </t>
3247  </list>
3251<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3253  Closed issues:
3254  <list style="symbols">
3255    <t>
3256      <eref target=""/>:
3257      "Requiring Allow in 405 responses"
3258    </t>
3259    <t>
3260      <eref target=""/>:
3261      "Status Code Registry"
3262    </t>
3263    <t>
3264      <eref target=""/>:
3265      "Redirection vs. Location"
3266    </t>
3267    <t>
3268      <eref target=""/>:
3269      "Cacheability of 303 response"
3270    </t>
3271    <t>
3272      <eref target=""/>:
3273      "305 Use Proxy"
3274    </t>
3275    <t>
3276      <eref target=""/>:
3277      "Classification for Allow header"
3278    </t>
3279    <t>
3280      <eref target=""/>:
3281      "PUT - 'store under' vs 'store at'"
3282    </t>
3283  </list>
3286  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3287  <list style="symbols">
3288    <t>
3289      Reference RFC 3984, and update header registrations for headers defined
3290      in this document.
3291    </t>
3292  </list>
3295  Ongoing work on ABNF conversion (<eref target=""/>):
3296  <list style="symbols">
3297    <t>
3298      Replace string literals when the string really is case-sensitive (method).
3299    </t>
3300  </list>
3304<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3306  Closed issues:
3307  <list style="symbols">
3308    <t>
3309      <eref target=""/>:
3310      "OPTIONS request bodies"
3311    </t>
3312    <t>
3313      <eref target=""/>:
3314      "Description of CONNECT should refer to RFC2817"
3315    </t>
3316    <t>
3317      <eref target=""/>:
3318      "Location Content-Location reference request/response mixup"
3319    </t>
3320  </list>
3323  Ongoing work on Method Registry (<eref target=""/>):
3324  <list style="symbols">
3325    <t>
3326      Added initial proposal for registration process, plus initial
3327      content (non-HTTP/1.1 methods to be added by a separate specification).
3328    </t>
3329  </list>
3333<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3335  Closed issues:
3336  <list style="symbols">
3337    <t>
3338      <eref target=""/>:
3339      "Content-*"
3340    </t>
3341    <t>
3342      <eref target=""/>:
3343      "RFC 2822 is updated by RFC 5322"
3344    </t>
3345  </list>
3348  Ongoing work on ABNF conversion (<eref target=""/>):
3349  <list style="symbols">
3350    <t>
3351      Use "/" instead of "|" for alternatives.
3352    </t>
3353    <t>
3354      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3355      whitespace ("OWS") and required whitespace ("RWS").
3356    </t>
3357    <t>
3358      Rewrite ABNFs to spell out whitespace rules, factor out
3359      header value format definitions.
3360    </t>
3361  </list>
3365<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
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