source: draft-ietf-httpbis/latest/p2-semantics.xml @ 374

Last change on this file since 374 was 374, checked in by julian.reschke@…, 14 years ago

Resolve #34: update to current URI spec, get rid of discussion of URI history (closes #34)

  • Property svn:eol-style set to native
File size: 144.0 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.04"/>.
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="DIGIT"/>
293  <x:anchor-alias value="quoted-string"/>
294  <x:anchor-alias value="token"/>
295  <x:anchor-alias value="OWS"/>
296  <x:anchor-alias value="RWS"/>
298  This specification uses the ABNF syntax defined in &notation-abnf; and
299  the core rules defined in &basic-rules;:
300  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
301  <eref target=""/>.</cref>
303<figure><artwork type="abnf2616">
304  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
306<figure><artwork type="abnf2616">
307  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
308  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
309  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
310  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
311  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
313<t anchor="abnf.dependencies">
314  <x:anchor-alias value="absolute-URI"/>
315  <x:anchor-alias value="Accept"/>
316  <x:anchor-alias value="Accept-Charset"/>
317  <x:anchor-alias value="Accept-Encoding"/>
318  <x:anchor-alias value="Accept-Language"/>
319  <x:anchor-alias value="Accept-Ranges"/>
320  <x:anchor-alias value="Age"/>
321  <x:anchor-alias value="Authorization"/>
322  <x:anchor-alias value="ETag"/>
323  <x:anchor-alias value="fragment"/>
324  <x:anchor-alias value="Host"/>
325  <x:anchor-alias value="HTTP-date"/>
326  <x:anchor-alias value="If-Match"/>
327  <x:anchor-alias value="If-Modified-Since"/>
328  <x:anchor-alias value="If-None-Match"/>
329  <x:anchor-alias value="If-Range"/>
330  <x:anchor-alias value="If-Unmodified-Since"/>
331  <x:anchor-alias value="product"/>
332  <x:anchor-alias value="Proxy-Authenticate"/>
333  <x:anchor-alias value="Proxy-Authorization"/>
334  <x:anchor-alias value="Range"/>
335  <x:anchor-alias value="relativeURI"/>
336  <x:anchor-alias value="TE"/>
337  <x:anchor-alias value="Vary"/>
338  <x:anchor-alias value="WWW-Authenticate"/>
339  The ABNF rules below are defined in other parts:
341<figure><!--Part1--><artwork type="abnf2616">
342  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
343  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
344  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
345  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
346  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
347  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &uri;&gt;
348  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
350<figure><!--Part3--><artwork type="abnf2616">
351  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
352  <x:ref>Accept-Charset</x:ref> =
353             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
354  <x:ref>Accept-Encoding</x:ref> =
355             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
356  <x:ref>Accept-Language</x:ref> =
357             &lt;Accept-Language, defined in &header-accept-language;&gt;
359<figure><!--Part4--><artwork type="abnf2616">
360  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
361  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
362  <x:ref>If-Modified-Since</x:ref> =
363             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
364  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
365  <x:ref>If-Unmodified-Since</x:ref> =
366             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
368<figure><!--Part5--><artwork type="abnf2616">
369  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
370  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
371  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
373<figure><!--Part6--><artwork type="abnf2616">
374  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
375  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
377<figure><artwork type="abnf2616">
378  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
379  <x:ref>Proxy-Authenticate</x:ref> =
380             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
381  <x:ref>Proxy-Authorization</x:ref> =
382             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
383  <x:ref>WWW-Authenticate</x:ref> =
384             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
388<section title="Method" anchor="method">
389  <x:anchor-alias value="Method"/>
390  <x:anchor-alias value="extension-method"/>
392   The Method  token indicates the method to be performed on the
393   resource identified by the Request-URI. The method is case-sensitive.
395<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
396  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
397                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
398                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
399                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
400                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
401                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
402                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
403                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
404                 / <x:ref>extension-method</x:ref>
405  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
408   The list of methods allowed by a resource can be specified in an
409   Allow header field (<xref target="header.allow"/>). The return code of the response
410   always notifies the client whether a method is currently allowed on a
411   resource, since the set of allowed methods can change dynamically. An
412   origin server &SHOULD; return the status code 405 (Method Not Allowed)
413   if the method is known by the origin server but not allowed for the
414   requested resource, and 501 (Not Implemented) if the method is
415   unrecognized or not implemented by the origin server. The methods GET
416   and HEAD &MUST; be supported by all general-purpose servers. All other
417   methods are &OPTIONAL;; however, if the above methods are implemented,
418   they &MUST; be implemented with the same semantics as those specified
419   in <xref target="method.definitions"/>.
422<section title="Method Registry" anchor="method.registry">
424  The HTTP Method Registry defines the name space for the Method token in the
425  Request line of an HTTP request.
428  Registrations &MUST; include the following fields:
429  <list style="symbols">
430    <t>Method Name (see <xref target="method"/>)</t>
431    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
432    <t>Pointer to specification text</t>
433  </list>
436  Values to be added to this name space are subject to IETF review
437  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
438  new method names should be traceable through statuses of either 'Obsoletes'
439  or 'Updates' to this document.
442  The registry itself is maintained at <eref target=""/>.
447<section title="Request Header Fields" anchor="request.header.fields">
448  <x:anchor-alias value="extension-code"/>
449  <x:anchor-alias value="request-header"/>
451   The request-header fields allow the client to pass additional
452   information about the request, and about the client itself, to the
453   server. These fields act as request modifiers, with semantics
454   equivalent to the parameters on a programming language method
455   invocation.
457<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
458  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
459                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
460                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
461                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
462                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
463                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
464                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
465                 / <x:ref>Host</x:ref>                     ; &header-host;
466                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
467                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
468                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
469                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
470                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
471                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
472                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
473                 / <x:ref>Range</x:ref>                    ; &header-range;
474                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
475                 / <x:ref>TE</x:ref>                       ; &header-te;
476                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
479   Request-header field names can be extended reliably only in
480   combination with a change in the protocol version. However, new or
481   experimental header fields &MAY; be given the semantics of request-header
482   fields if all parties in the communication recognize them to
483   be request-header fields. Unrecognized header fields are treated as
484   entity-header fields.
488<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
489  <x:anchor-alias value="Reason-Phrase"/>
490  <x:anchor-alias value="Status-Code"/>
492   The Status-Code element is a 3-digit integer result code of the
493   attempt to understand and satisfy the request. The status codes listed
494   below are defined in <xref target=""/>.
495   The Reason-Phrase is intended to give a short
496   textual description of the Status-Code. The Status-Code is intended
497   for use by automata and the Reason-Phrase is intended for the human
498   user. The client is not required to examine or display the Reason-Phrase.
501   The individual values of the numeric status codes defined for
502   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
503   presented below. The reason phrases listed here are only
504   recommendations -- they &MAY; be replaced by local equivalents without
505   affecting the protocol.
507<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"/>
508  <x:ref>Status-Code</x:ref>    =
509         "100"  ; <xref target="status.100"/>: Continue
510       / "101"  ; <xref target="status.101"/>: Switching Protocols
511       / "200"  ; <xref target="status.200"/>: OK
512       / "201"  ; <xref target="status.201"/>: Created
513       / "202"  ; <xref target="status.202"/>: Accepted
514       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
515       / "204"  ; <xref target="status.204"/>: No Content
516       / "205"  ; <xref target="status.205"/>: Reset Content
517       / "206"  ; <xref target="status.206"/>: Partial Content
518       / "300"  ; <xref target="status.300"/>: Multiple Choices
519       / "301"  ; <xref target="status.301"/>: Moved Permanently
520       / "302"  ; <xref target="status.302"/>: Found
521       / "303"  ; <xref target="status.303"/>: See Other
522       / "304"  ; <xref target="status.304"/>: Not Modified
523       / "305"  ; <xref target="status.305"/>: Use Proxy
524       / "307"  ; <xref target="status.307"/>: Temporary Redirect
525       / "400"  ; <xref target="status.400"/>: Bad Request
526       / "401"  ; <xref target="status.401"/>: Unauthorized
527       / "402"  ; <xref target="status.402"/>: Payment Required
528       / "403"  ; <xref target="status.403"/>: Forbidden
529       / "404"  ; <xref target="status.404"/>: Not Found
530       / "405"  ; <xref target="status.405"/>: Method Not Allowed
531       / "406"  ; <xref target="status.406"/>: Not Acceptable
532       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
533       / "408"  ; <xref target="status.408"/>: Request Time-out
534       / "409"  ; <xref target="status.409"/>: Conflict
535       / "410"  ; <xref target="status.410"/>: Gone
536       / "411"  ; <xref target="status.411"/>: Length Required
537       / "412"  ; <xref target="status.412"/>: Precondition Failed
538       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
539       / "414"  ; <xref target="status.414"/>: Request-URI Too Large
540       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
541       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
542       / "417"  ; <xref target="status.417"/>: Expectation Failed
543       / "500"  ; <xref target="status.500"/>: Internal Server Error
544       / "501"  ; <xref target="status.501"/>: Not Implemented
545       / "502"  ; <xref target="status.502"/>: Bad Gateway
546       / "503"  ; <xref target="status.503"/>: Service Unavailable
547       / "504"  ; <xref target="status.504"/>: Gateway Time-out
548       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
549       / <x:ref>extension-code</x:ref>
551  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
552  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
555   HTTP status codes are extensible. HTTP applications are not required
556   to understand the meaning of all registered status codes, though such
557   understanding is obviously desirable. However, applications &MUST;
558   understand the class of any status code, as indicated by the first
559   digit, and treat any unrecognized response as being equivalent to the
560   x00 status code of that class, with the exception that an
561   unrecognized response &MUST-NOT; be cached. For example, if an
562   unrecognized status code of 431 is received by the client, it can
563   safely assume that there was something wrong with its request and
564   treat the response as if it had received a 400 status code. In such
565   cases, user agents &SHOULD; present to the user the entity returned
566   with the response, since that entity is likely to include human-readable
567   information which will explain the unusual status.
570<section title="Status Code Registry" anchor="status.code.registry">
572  The HTTP Status Code Registry defines the name space for the Status-Code
573  token in the Status line of an HTTP response.
576  Values to be added to this name space are subject to IETF review
577  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
578  new status codes should be traceable through statuses of either 'Obsoletes'
579  or 'Updates' to this document.
582  The registry itself is maintained at <eref target=""/>.
588<section title="Response Header Fields" anchor="response.header.fields">
589  <x:anchor-alias value="response-header"/>
591   The response-header fields allow the server to pass additional
592   information about the response which cannot be placed in the Status-Line.
593   These header fields give information about the server and about
594   further access to the resource identified by the Request-URI.
596<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
597  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
598                  / <x:ref>Age</x:ref>                     ; &header-age;
599                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
600                  / <x:ref>ETag</x:ref>                    ; &header-etag;
601                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
602                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
603                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
604                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
605                  / <x:ref>Vary</x:ref>                    ; &header-vary;
606                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
609   Response-header field names can be extended reliably only in
610   combination with a change in the protocol version. However, new or
611   experimental header fields &MAY; be given the semantics of response-header
612   fields if all parties in the communication recognize them to
613   be response-header fields. Unrecognized header fields are treated as
614   entity-header fields.
618<section title="Entity" anchor="entity">
620   Request and Response messages &MAY; transfer an entity if not otherwise
621   restricted by the request method or response status code. An entity
622   consists of entity-header fields and an entity-body, although some
623   responses will only include the entity-headers. HTTP entity-body and
624   entity-header fields are defined in &payload;.
627   An entity-body is only present in a message when a message-body is
628   present, as described in &message-body;. The entity-body is obtained
629   from the message-body by decoding any Transfer-Encoding that might
630   have been applied to ensure safe and proper transfer of the message.
635<section title="Method Definitions" anchor="method.definitions">
637   The set of common methods for HTTP/1.1 is defined below. Although
638   this set can be expanded, additional methods cannot be assumed to
639   share the same semantics for separately extended clients and servers.
642<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
644<section title="Safe Methods" anchor="safe.methods">
645<iref item="Safe Methods" primary="true"/>
647   Implementors should be aware that the software represents the user in
648   their interactions over the Internet, and should be careful to allow
649   the user to be aware of any actions they might take which may have an
650   unexpected significance to themselves or others.
653   In particular, the convention has been established that the GET and
654   HEAD methods &SHOULD-NOT;  have the significance of taking an action
655   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
656   This allows user agents to represent other methods, such as POST, PUT
657   and DELETE, in a special way, so that the user is made aware of the
658   fact that a possibly unsafe action is being requested.
661   Naturally, it is not possible to ensure that the server does not
662   generate side-effects as a result of performing a GET request; in
663   fact, some dynamic resources consider that a feature. The important
664   distinction here is that the user did not request the side-effects,
665   so therefore cannot be held accountable for them.
669<section title="Idempotent Methods" anchor="idempotent.methods">
670<iref item="Idempotent Methods" primary="true"/>
672   Methods can also have the property of "idempotence" in that (aside
673   from error or expiration issues) the side-effects of N &gt; 0 identical
674   requests is the same as for a single request. The methods GET, HEAD,
675   PUT and DELETE share this property. Also, the methods OPTIONS and
676   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
679   However, it is possible that a sequence of several requests is non-idempotent,
680   even if all of the methods executed in that sequence are
681   idempotent. (A sequence is idempotent if a single execution of the
682   entire sequence always yields a result that is not changed by a
683   reexecution of all, or part, of that sequence.) For example, a
684   sequence is non-idempotent if its result depends on a value that is
685   later modified in the same sequence.
688   A sequence that never has side effects is idempotent, by definition
689   (provided that no concurrent operations are being executed on the
690   same set of resources).
695<section title="OPTIONS" anchor="OPTIONS">
696  <rdf:Description>
697    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
698  </rdf:Description>
699  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
700  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
702   The OPTIONS method represents a request for information about the
703   communication options available on the request/response chain
704   identified by the Request-URI. This method allows the client to
705   determine the options and/or requirements associated with a resource,
706   or the capabilities of a server, without implying a resource action
707   or initiating a resource retrieval.
710   Responses to this method are not cacheable.
713   If the OPTIONS request includes an entity-body (as indicated by the
714   presence of Content-Length or Transfer-Encoding), then the media type
715   &MUST; be indicated by a Content-Type field. Although this
716   specification does not define any use for such a body, future
717   extensions to HTTP might use the OPTIONS body to make more detailed
718   queries on the server.
721   If the Request-URI is an asterisk ("*"), the OPTIONS request is
722   intended to apply to the server in general rather than to a specific
723   resource. Since a server's communication options typically depend on
724   the resource, the "*" request is only useful as a "ping" or "no-op"
725   type of method; it does nothing beyond allowing the client to test
726   the capabilities of the server. For example, this can be used to test
727   a proxy for HTTP/1.1 compliance (or lack thereof).
730   If the Request-URI is not an asterisk, the OPTIONS request applies
731   only to the options that are available when communicating with that
732   resource.
735   A 200 response &SHOULD; include any header fields that indicate
736   optional features implemented by the server and applicable to that
737   resource (e.g., Allow), possibly including extensions not defined by
738   this specification. The response body, if any, &SHOULD; also include
739   information about the communication options. The format for such a
740   body is not defined by this specification, but might be defined by
741   future extensions to HTTP. Content negotiation &MAY; be used to select
742   the appropriate response format. If no response body is included, the
743   response &MUST; include a Content-Length field with a field-value of
744   "0".
747   The Max-Forwards request-header field &MAY; be used to target a
748   specific proxy in the request chain. When a proxy receives an OPTIONS
749   request on an absolute-URI for which request forwarding is permitted,
750   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
751   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
752   instead, the proxy &SHOULD; respond with its own communication options.
753   If the Max-Forwards field-value is an integer greater than zero, the
754   proxy &MUST; decrement the field-value when it forwards the request. If
755   no Max-Forwards field is present in the request, then the forwarded
756   request &MUST-NOT; include a Max-Forwards field.
760<section title="GET" anchor="GET">
761  <rdf:Description>
762    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
763  </rdf:Description>
764  <iref primary="true" item="GET method" x:for-anchor=""/>
765  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
767   The GET method means retrieve whatever information (in the form of an
768   entity) is identified by the Request-URI. If the Request-URI refers
769   to a data-producing process, it is the produced data which shall be
770   returned as the entity in the response and not the source text of the
771   process, unless that text happens to be the output of the process.
774   The semantics of the GET method change to a "conditional GET" if the
775   request message includes an If-Modified-Since, If-Unmodified-Since,
776   If-Match, If-None-Match, or If-Range header field. A conditional GET
777   method requests that the entity be transferred only under the
778   circumstances described by the conditional header field(s). The
779   conditional GET method is intended to reduce unnecessary network
780   usage by allowing cached entities to be refreshed without requiring
781   multiple requests or transferring data already held by the client.
784   The semantics of the GET method change to a "partial GET" if the
785   request message includes a Range header field. A partial GET requests
786   that only part of the entity be transferred, as described in &header-range;.
787   The partial GET method is intended to reduce unnecessary
788   network usage by allowing partially-retrieved entities to be
789   completed without transferring data already held by the client.
792   The response to a GET request is cacheable if and only if it meets
793   the requirements for HTTP caching described in &caching;.
796   See <xref target=""/> for security considerations when used for forms.
800<section title="HEAD" anchor="HEAD">
801  <rdf:Description>
802    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
803  </rdf:Description>
804  <iref primary="true" item="HEAD method" x:for-anchor=""/>
805  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
807   The HEAD method is identical to GET except that the server &MUST-NOT;
808   return a message-body in the response. The metainformation contained
809   in the HTTP headers in response to a HEAD request &SHOULD; be identical
810   to the information sent in response to a GET request. This method can
811   be used for obtaining metainformation about the entity implied by the
812   request without transferring the entity-body itself. This method is
813   often used for testing hypertext links for validity, accessibility,
814   and recent modification.
817   The response to a HEAD request &MAY; be cacheable in the sense that the
818   information contained in the response &MAY; be used to update a
819   previously cached entity from that resource. If the new field values
820   indicate that the cached entity differs from the current entity (as
821   would be indicated by a change in Content-Length, Content-MD5, ETag
822   or Last-Modified), then the cache &MUST; treat the cache entry as
823   stale.
827<section title="POST" anchor="POST">
828  <iref primary="true" item="POST method" x:for-anchor=""/>
829  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
831   The POST method is used to request that the origin server accept the
832   entity enclosed in the request as data to be processed by the resource
833   identified by the Request-URI in the Request-Line. POST is designed
834   to allow a uniform method to cover the following functions:
835  <list style="symbols">
836    <t>
837      Annotation of existing resources;
838    </t>
839    <t>
840        Posting a message to a bulletin board, newsgroup, mailing list,
841        or similar group of articles;
842    </t>
843    <t>
844        Providing a block of data, such as the result of submitting a
845        form, to a data-handling process;
846    </t>
847    <t>
848        Extending a database through an append operation.
849    </t>
850  </list>
853   The actual function performed by the POST method is determined by the
854   server and is usually dependent on the Request-URI.
857   The action performed by the POST method might not result in a
858   resource that can be identified by a URI. In this case, either 200
859   (OK) or 204 (No Content) is the appropriate response status,
860   depending on whether or not the response includes an entity that
861   describes the result.
864   If a resource has been created on the origin server, the response
865   &SHOULD; be 201 (Created) and contain an entity which describes the
866   status of the request and refers to the new resource, and a Location
867   header (see <xref target="header.location"/>).
870   Responses to this method are not cacheable, unless the response
871   includes appropriate Cache-Control or Expires header fields. However,
872   the 303 (See Other) response can be used to direct the user agent to
873   retrieve a cacheable resource.
877<section title="PUT" anchor="PUT">
878  <iref primary="true" item="PUT method" x:for-anchor=""/>
879  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
881   The PUT method requests that the enclosed entity be stored at the
882   supplied Request-URI. If the Request-URI refers to an already
883   existing resource, the enclosed entity &SHOULD; be considered as a
884   modified version of the one residing on the origin server. If the
885   Request-URI does not point to an existing resource, and that URI is
886   capable of being defined as a new resource by the requesting user
887   agent, the origin server can create the resource with that URI. If a
888   new resource is created at the Request-URI, the origin server &MUST;
889         inform the user agent
890   via the 201 (Created) response. If an existing resource is modified,
891   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
892   to indicate successful completion of the request. If the resource
893   could not be created or modified with the Request-URI, an appropriate
894   error response &SHOULD; be given that reflects the nature of the
895   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
896   headers (headers starting with the prefix 'Content-') that it does
897   not understand or implement
898   and &MUST; return a 501 (Not Implemented) response in such cases.
901   If the request passes through a cache and the Request-URI identifies
902   one or more currently cached entities, those entries &SHOULD; be
903   treated as stale. Responses to this method are not cacheable.
906   The fundamental difference between the POST and PUT requests is
907   reflected in the different meaning of the Request-URI. The URI in a
908   POST request identifies the resource that will handle the enclosed
909   entity. That resource might be a data-accepting process, a gateway to
910   some other protocol, or a separate entity that accepts annotations.
911   In contrast, the URI in a PUT request identifies the entity enclosed
912   with the request -- the user agent knows what URI is intended and the
913   server &MUST-NOT; attempt to apply the request to some other resource.
914   If the server desires that the request be applied to a different URI,
915   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
916   then make its own decision regarding whether or not to redirect the
917   request.
920   A single resource &MAY; be identified by many different URIs. For
921   example, an article might have a URI for identifying "the current
922   version" which is separate from the URI identifying each particular
923   version. In this case, a PUT request on a general URI might result in
924   several other URIs being defined by the origin server.
927   HTTP/1.1 does not define how a PUT method affects the state of an
928   origin server.
931   Unless otherwise specified for a particular entity-header, the
932   entity-headers in the PUT request &SHOULD; be applied to the resource
933   created or modified by the PUT.
937<section title="DELETE" anchor="DELETE">
938  <iref primary="true" item="DELETE method" x:for-anchor=""/>
939  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
941   The DELETE method requests that the origin server delete the resource
942   identified by the Request-URI. This method &MAY; be overridden by human
943   intervention (or other means) on the origin server. The client cannot
944   be guaranteed that the operation has been carried out, even if the
945   status code returned from the origin server indicates that the action
946   has been completed successfully. However, the server &SHOULD-NOT;
947   indicate success unless, at the time the response is given, it
948   intends to delete the resource or move it to an inaccessible
949   location.
952   A successful response &SHOULD; be 200 (OK) if the response includes an
953   entity describing the status, 202 (Accepted) if the action has not
954   yet been enacted, or 204 (No Content) if the action has been enacted
955   but the response does not include an entity.
958   If the request passes through a cache and the Request-URI identifies
959   one or more currently cached entities, those entries &SHOULD; be
960   treated as stale. Responses to this method are not cacheable.
964<section title="TRACE" anchor="TRACE">
965  <rdf:Description>
966    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
967  </rdf:Description>
968  <iref primary="true" item="TRACE method" x:for-anchor=""/>
969  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
971   The TRACE method is used to invoke a remote, application-layer loop-back
972   of the request message. The final recipient of the request
973   &SHOULD; reflect the message received back to the client as the
974   entity-body of a 200 (OK) response. The final recipient is either the
975   origin server or the first proxy or gateway to receive a Max-Forwards
976   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
977   &MUST-NOT; include an entity.
980   TRACE allows the client to see what is being received at the other
981   end of the request chain and use that data for testing or diagnostic
982   information. The value of the Via header field (&header-via;) is of
983   particular interest, since it acts as a trace of the request chain.
984   Use of the Max-Forwards header field allows the client to limit the
985   length of the request chain, which is useful for testing a chain of
986   proxies forwarding messages in an infinite loop.
989   If the request is valid, the response &SHOULD; contain the entire
990   request message in the entity-body, with a Content-Type of
991   "message/http" (see &media-type-message-http;). Responses to this method
992   &MUST-NOT; be cached.
996<section title="CONNECT" anchor="CONNECT">
997  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
998  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1000   This specification reserves the method name CONNECT for use with a
1001   proxy that can dynamically switch to being a tunnel (e.g. SSL
1002   tunneling <xref target="RFC2817"/>).
1008<section title="Status Code Definitions" anchor="">
1010   Each Status-Code is described below, including a description of which
1011   method(s) it can follow and any metainformation required in the
1012   response.
1015<section title="Informational 1xx" anchor="status.1xx">
1017   This class of status code indicates a provisional response,
1018   consisting only of the Status-Line and optional headers, and is
1019   terminated by an empty line. There are no required headers for this
1020   class of status code. Since HTTP/1.0 did not define any 1xx status
1021   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1022   except under experimental conditions.
1025   A client &MUST; be prepared to accept one or more 1xx status responses
1026   prior to a regular response, even if the client does not expect a 100
1027   (Continue) status message. Unexpected 1xx status responses &MAY; be
1028   ignored by a user agent.
1031   Proxies &MUST; forward 1xx responses, unless the connection between the
1032   proxy and its client has been closed, or unless the proxy itself
1033   requested the generation of the 1xx response. (For example, if a
1034   proxy adds a "Expect: 100-continue" field when it forwards a request,
1035   then it need not forward the corresponding 100 (Continue)
1036   response(s).)
1039<section title="100 Continue" anchor="status.100">
1040  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1041  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1043   The client &SHOULD; continue with its request. This interim response is
1044   used to inform the client that the initial part of the request has
1045   been received and has not yet been rejected by the server. The client
1046   &SHOULD; continue by sending the remainder of the request or, if the
1047   request has already been completed, ignore this response. The server
1048   &MUST; send a final response after the request has been completed. See
1049   &use100; for detailed discussion of the use and handling of this
1050   status code.
1054<section title="101 Switching Protocols" anchor="status.101">
1055  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1056  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1058   The server understands and is willing to comply with the client's
1059   request, via the Upgrade message header field (&header-upgrade;), for a
1060   change in the application protocol being used on this connection. The
1061   server will switch protocols to those defined by the response's
1062   Upgrade header field immediately after the empty line which
1063   terminates the 101 response.
1066   The protocol &SHOULD; be switched only when it is advantageous to do
1067   so. For example, switching to a newer version of HTTP is advantageous
1068   over older versions, and switching to a real-time, synchronous
1069   protocol might be advantageous when delivering resources that use
1070   such features.
1075<section title="Successful 2xx" anchor="status.2xx">
1077   This class of status code indicates that the client's request was
1078   successfully received, understood, and accepted.
1081<section title="200 OK" anchor="status.200">
1082  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1083  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1085   The request has succeeded. The information returned with the response
1086   is dependent on the method used in the request, for example:
1087  <list style="hanging">
1088    <t hangText="GET">
1089          an entity corresponding to the requested resource is sent in
1090          the response;
1091    </t>
1092    <t hangText="HEAD">
1093          the entity-header fields corresponding to the requested
1094          resource are sent in the response without any message-body;
1095    </t>
1096    <t hangText="POST">
1097      an entity describing or containing the result of the action;
1098    </t>
1099    <t hangText="TRACE">
1100      an entity containing the request message as received by the
1101      end server.
1102    </t>
1103  </list>
1107<section title="201 Created" anchor="status.201">
1108  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1109  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1111   The request has been fulfilled and resulted in a new resource being
1112   created. The newly created resource can be referenced by the URI(s)
1113   returned in the entity of the response, with the most specific URI
1114   for the resource given by a Location header field. The response
1115   &SHOULD; include an entity containing a list of resource
1116   characteristics and location(s) from which the user or user agent can
1117   choose the one most appropriate. The entity format is specified by
1118   the media type given in the Content-Type header field. The origin
1119   server &MUST; create the resource before returning the 201 status code.
1120   If the action cannot be carried out immediately, the server &SHOULD;
1121   respond with 202 (Accepted) response instead.
1124   A 201 response &MAY; contain an ETag response header field indicating
1125   the current value of the entity tag for the requested variant just
1126   created, see &header-etag;.
1130<section title="202 Accepted" anchor="status.202">
1131  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1132  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1134   The request has been accepted for processing, but the processing has
1135   not been completed.  The request might or might not eventually be
1136   acted upon, as it might be disallowed when processing actually takes
1137   place. There is no facility for re-sending a status code from an
1138   asynchronous operation such as this.
1141   The 202 response is intentionally non-committal. Its purpose is to
1142   allow a server to accept a request for some other process (perhaps a
1143   batch-oriented process that is only run once per day) without
1144   requiring that the user agent's connection to the server persist
1145   until the process is completed. The entity returned with this
1146   response &SHOULD; include an indication of the request's current status
1147   and either a pointer to a status monitor or some estimate of when the
1148   user can expect the request to be fulfilled.
1152<section title="203 Non-Authoritative Information" anchor="status.203">
1153  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1154  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1156   The returned metainformation in the entity-header is not the
1157   definitive set as available from the origin server, but is gathered
1158   from a local or a third-party copy. The set presented &MAY; be a subset
1159   or superset of the original version. For example, including local
1160   annotation information about the resource might result in a superset
1161   of the metainformation known by the origin server. Use of this
1162   response code is not required and is only appropriate when the
1163   response would otherwise be 200 (OK).
1167<section title="204 No Content" anchor="status.204">
1168  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1169  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1171   The server has fulfilled the request but does not need to return an
1172   entity-body, and might want to return updated metainformation. The
1173   response &MAY; include new or updated metainformation in the form of
1174   entity-headers, which if present &SHOULD; be associated with the
1175   requested variant.
1178   If the client is a user agent, it &SHOULD-NOT;  change its document view
1179   from that which caused the request to be sent. This response is
1180   primarily intended to allow input for actions to take place without
1181   causing a change to the user agent's active document view, although
1182   any new or updated metainformation &SHOULD; be applied to the document
1183   currently in the user agent's active view.
1186   The 204 response &MUST-NOT; include a message-body, and thus is always
1187   terminated by the first empty line after the header fields.
1191<section title="205 Reset Content" anchor="status.205">
1192  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1193  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1195   The server has fulfilled the request and the user agent &SHOULD; reset
1196   the document view which caused the request to be sent. This response
1197   is primarily intended to allow input for actions to take place via
1198   user input, followed by a clearing of the form in which the input is
1199   given so that the user can easily initiate another input action. The
1200   response &MUST-NOT; include an entity.
1204<section title="206 Partial Content" anchor="status.206">
1205  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1206  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1208   The server has fulfilled the partial GET request for the resource
1209   and the enclosed entity is a partial representation as defined in &range;.
1214<section title="Redirection 3xx" anchor="status.3xx">
1216   This class of status code indicates that further action needs to be
1217   taken by the user agent in order to fulfill the request.  The action
1218   required &MAY; be carried out by the user agent without interaction
1219   with the user if and only if the method used in the second request is
1220   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1221   such loops generate network traffic for each redirection.
1222  <list><t>
1223      <x:h>Note:</x:h> previous versions of this specification recommended a
1224      maximum of five redirections. Content developers should be aware
1225      that there might be clients that implement such a fixed
1226      limitation.
1227  </t></list>
1230<section title="300 Multiple Choices" anchor="status.300">
1231  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1232  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1234   The requested resource corresponds to any one of a set of
1235   representations, each with its own specific location, and agent-driven
1236   negotiation information (&content-negotiation;) is being provided so that
1237   the user (or user agent) can select a preferred representation and
1238   redirect its request to that location.
1241   Unless it was a HEAD request, the response &SHOULD; include an entity
1242   containing a list of resource characteristics and location(s) from
1243   which the user or user agent can choose the one most appropriate. The
1244   entity format is specified by the media type given in the Content-Type
1245   header field. Depending upon the format and the capabilities of
1246   the user agent, selection of the most appropriate choice &MAY; be
1247   performed automatically. However, this specification does not define
1248   any standard for such automatic selection.
1251   If the server has a preferred choice of representation, it &SHOULD;
1252   include the specific URI for that representation in the Location
1253   field; user agents &MAY; use the Location field value for automatic
1254   redirection. This response is cacheable unless indicated otherwise.
1258<section title="301 Moved Permanently" anchor="status.301">
1259  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1260  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1262   The requested resource has been assigned a new permanent URI and any
1263   future references to this resource &SHOULD; use one of the returned
1264   URIs.  Clients with link editing capabilities ought to automatically
1265   re-link references to the Request-URI to one or more of the new
1266   references returned by the server, where possible. This response is
1267   cacheable unless indicated otherwise.
1270   The new permanent URI &SHOULD; be given by the Location field in the
1271   response. Unless the request method was HEAD, the entity of the
1272   response &SHOULD; contain a short hypertext note with a hyperlink to
1273   the new URI(s).
1276   If the 301 status code is received in response to a request method
1277   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1278   then the request &MAY; be automatically redirected by the user agent without
1279   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1280   request unless it can be confirmed by the user, since this might
1281   change the conditions under which the request was issued.
1282  <list><t>
1283      <x:h>Note:</x:h> When automatically redirecting a POST request after
1284      receiving a 301 status code, some existing HTTP/1.0 user agents
1285      will erroneously change it into a GET request.
1286  </t></list>
1290<section title="302 Found" anchor="status.302">
1291  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1292  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1294   The requested resource resides temporarily under a different URI.
1295   Since the redirection might be altered on occasion, the client &SHOULD;
1296   continue to use the Request-URI for future requests.  This response
1297   is only cacheable if indicated by a Cache-Control or Expires header
1298   field.
1301   The temporary URI &SHOULD; be given by the Location field in the
1302   response. Unless the request method was HEAD, the entity of the
1303   response &SHOULD; contain a short hypertext note with a hyperlink to
1304   the new URI(s).
1307   If the 302 status code is received in response to a request method
1308   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1309   then the request &MAY; be automatically redirected by the user agent without
1310   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1311   request unless it can be confirmed by the user, since this might
1312   change the conditions under which the request was issued.
1313  <list><t>
1314      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1315      to change the method on the redirected request.  However, most
1316      existing user agent implementations treat 302 as if it were a 303
1317      response, performing a GET on the Location field-value regardless
1318      of the original request method. The status codes 303 and 307 have
1319      been added for servers that wish to make unambiguously clear which
1320      kind of reaction is expected of the client.
1321  </t></list>
1325<section title="303 See Other" anchor="status.303">
1326  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1327  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1329   The server directs the user agent to a different resource, indicated
1330   by a URI in the Location header field, that provides an indirect
1331   response to the original request.  The user agent &MAY; perform a GET
1332   request on the URI in the Location field in order to obtain a
1333   representation corresponding to the response, be redirected again,
1334   or end with an error status.  The Location URI is not a substitute
1335   reference for the originally requested resource.
1338   The 303 status is generally applicable to any HTTP method.  It is
1339   primarily used to allow the output of a POST action to redirect
1340   the user agent to a selected resource, since doing so provides the
1341   information corresponding to the POST response in a form that
1342   can be separately identified, bookmarked, and cached independent
1343   of the original request.
1346   A 303 response to a GET request indicates that the requested
1347   resource does not have a representation of its own that can be
1348   transferred by the server over HTTP.  The Location URI indicates a
1349   resource that is descriptive of the requested resource such that
1350   the follow-on representation may be useful without implying that
1351   it adequately represents the previously requested resource.
1352   Note that answers to the questions of what can be represented, what
1353   representations are adequate, and what might be a useful description
1354   are outside the scope of HTTP and thus entirely determined by the
1355   resource owner(s).
1358   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1359   cacheable by Cache-Control or Expires header fields.  Except for
1360   responses to a HEAD request, the entity of a 303 response &SHOULD;
1361   contain a short hypertext note with a hyperlink to the Location URI.
1365<section title="304 Not Modified" anchor="status.304">
1366  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1367  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1369   The response to the request has not been modified since the conditions
1370   indicated by the client's conditional GET request, as defined in &conditional;.
1374<section title="305 Use Proxy" anchor="status.305">
1375  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1376  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1378   The 305 status was defined in a previous version of this specification
1379   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1383<section title="306 (Unused)" anchor="status.306">
1384  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1385  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1387   The 306 status code was used in a previous version of the
1388   specification, is no longer used, and the code is reserved.
1392<section title="307 Temporary Redirect" anchor="status.307">
1393  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1394  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1396   The requested resource resides temporarily under a different URI.
1397   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1398   continue to use the Request-URI for future requests.  This response
1399   is only cacheable if indicated by a Cache-Control or Expires header
1400   field.
1403   The temporary URI &SHOULD; be given by the Location field in the
1404   response. Unless the request method was HEAD, the entity of the
1405   response &SHOULD; contain a short hypertext note with a hyperlink to
1406   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1407   understand the 307 status. Therefore, the note &SHOULD; contain the
1408   information necessary for a user to repeat the original request on
1409   the new URI.
1412   If the 307 status code is received in response to a request method
1413   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1414   then the request &MAY; be automatically redirected by the user agent without
1415   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1416   request unless it can be confirmed by the user, since this might
1417   change the conditions under which the request was issued.
1422<section title="Client Error 4xx" anchor="status.4xx">
1424   The 4xx class of status code is intended for cases in which the
1425   client seems to have erred. Except when responding to a HEAD request,
1426   the server &SHOULD; include an entity containing an explanation of the
1427   error situation, and whether it is a temporary or permanent
1428   condition. These status codes are applicable to any request method.
1429   User agents &SHOULD; display any included entity to the user.
1432   If the client is sending data, a server implementation using TCP
1433   &SHOULD; be careful to ensure that the client acknowledges receipt of
1434   the packet(s) containing the response, before the server closes the
1435   input connection. If the client continues sending data to the server
1436   after the close, the server's TCP stack will send a reset packet to
1437   the client, which may erase the client's unacknowledged input buffers
1438   before they can be read and interpreted by the HTTP application.
1441<section title="400 Bad Request" anchor="status.400">
1442  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1443  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1445   The request could not be understood by the server due to malformed
1446   syntax. The client &SHOULD-NOT;  repeat the request without
1447   modifications.
1451<section title="401 Unauthorized" anchor="status.401">
1452  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1453  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1455   The request requires user authentication (see &auth;).
1459<section title="402 Payment Required" anchor="status.402">
1460  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1461  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1463   This code is reserved for future use.
1467<section title="403 Forbidden" anchor="status.403">
1468  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1469  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1471   The server understood the request, but is refusing to fulfill it.
1472   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1473   If the request method was not HEAD and the server wishes to make
1474   public why the request has not been fulfilled, it &SHOULD; describe the
1475   reason for the refusal in the entity.  If the server does not wish to
1476   make this information available to the client, the status code 404
1477   (Not Found) can be used instead.
1481<section title="404 Not Found" anchor="status.404">
1482  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1483  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1485   The server has not found anything matching the Request-URI. No
1486   indication is given of whether the condition is temporary or
1487   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1488   knows, through some internally configurable mechanism, that an old
1489   resource is permanently unavailable and has no forwarding address.
1490   This status code is commonly used when the server does not wish to
1491   reveal exactly why the request has been refused, or when no other
1492   response is applicable.
1496<section title="405 Method Not Allowed" anchor="status.405">
1497  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1498  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1500   The method specified in the Request-Line is not allowed for the
1501   resource identified by the Request-URI. The response &MUST; include an
1502   Allow header containing a list of valid methods for the requested
1503   resource.
1507<section title="406 Not Acceptable" anchor="status.406">
1508  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1509  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1511   The resource identified by the request is only capable of generating
1512   response entities which have content characteristics not acceptable
1513   according to the accept headers sent in the request.
1516   Unless it was a HEAD request, the response &SHOULD; include an entity
1517   containing a list of available entity characteristics and location(s)
1518   from which the user or user agent can choose the one most
1519   appropriate. The entity format is specified by the media type given
1520   in the Content-Type header field. Depending upon the format and the
1521   capabilities of the user agent, selection of the most appropriate
1522   choice &MAY; be performed automatically. However, this specification
1523   does not define any standard for such automatic selection.
1524  <list><t>
1525      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1526      not acceptable according to the accept headers sent in the
1527      request. In some cases, this may even be preferable to sending a
1528      406 response. User agents are encouraged to inspect the headers of
1529      an incoming response to determine if it is acceptable.
1530  </t></list>
1533   If the response could be unacceptable, a user agent &SHOULD;
1534   temporarily stop receipt of more data and query the user for a
1535   decision on further actions.
1539<section title="407 Proxy Authentication Required" anchor="status.407">
1540  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1541  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1543   This code is similar to 401 (Unauthorized), but indicates that the
1544   client must first authenticate itself with the proxy (see &auth;).
1548<section title="408 Request Timeout" anchor="status.408">
1549  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1550  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1552   The client did not produce a request within the time that the server
1553   was prepared to wait. The client &MAY; repeat the request without
1554   modifications at any later time.
1558<section title="409 Conflict" anchor="status.409">
1559  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1560  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1562   The request could not be completed due to a conflict with the current
1563   state of the resource. This code is only allowed in situations where
1564   it is expected that the user might be able to resolve the conflict
1565   and resubmit the request. The response body &SHOULD; include enough
1566   information for the user to recognize the source of the conflict.
1567   Ideally, the response entity would include enough information for the
1568   user or user agent to fix the problem; however, that might not be
1569   possible and is not required.
1572   Conflicts are most likely to occur in response to a PUT request. For
1573   example, if versioning were being used and the entity being PUT
1574   included changes to a resource which conflict with those made by an
1575   earlier (third-party) request, the server might use the 409 response
1576   to indicate that it can't complete the request. In this case, the
1577   response entity would likely contain a list of the differences
1578   between the two versions in a format defined by the response
1579   Content-Type.
1583<section title="410 Gone" anchor="status.410">
1584  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1585  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1587   The requested resource is no longer available at the server and no
1588   forwarding address is known. This condition is expected to be
1589   considered permanent. Clients with link editing capabilities &SHOULD;
1590   delete references to the Request-URI after user approval. If the
1591   server does not know, or has no facility to determine, whether or not
1592   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1593   used instead. This response is cacheable unless indicated otherwise.
1596   The 410 response is primarily intended to assist the task of web
1597   maintenance by notifying the recipient that the resource is
1598   intentionally unavailable and that the server owners desire that
1599   remote links to that resource be removed. Such an event is common for
1600   limited-time, promotional services and for resources belonging to
1601   individuals no longer working at the server's site. It is not
1602   necessary to mark all permanently unavailable resources as "gone" or
1603   to keep the mark for any length of time -- that is left to the
1604   discretion of the server owner.
1608<section title="411 Length Required" anchor="status.411">
1609  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1610  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1612   The server refuses to accept the request without a defined Content-Length.
1613   The client &MAY; repeat the request if it adds a valid
1614   Content-Length header field containing the length of the message-body
1615   in the request message.
1619<section title="412 Precondition Failed" anchor="status.412">
1620  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1621  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1623   The precondition given in one or more of the request-header fields
1624   evaluated to false when it was tested on the server, as defined in
1625   &conditional;.
1629<section title="413 Request Entity Too Large" anchor="status.413">
1630  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1631  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1633   The server is refusing to process a request because the request
1634   entity is larger than the server is willing or able to process. The
1635   server &MAY; close the connection to prevent the client from continuing
1636   the request.
1639   If the condition is temporary, the server &SHOULD; include a Retry-After
1640   header field to indicate that it is temporary and after what
1641   time the client &MAY; try again.
1645<section title="414 Request-URI Too Long" anchor="status.414">
1646  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1647  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1649   The server is refusing to service the request because the Request-URI
1650   is longer than the server is willing to interpret. This rare
1651   condition is only likely to occur when a client has improperly
1652   converted a POST request to a GET request with long query
1653   information, when the client has descended into a URI "black hole" of
1654   redirection (e.g., a redirected URI prefix that points to a suffix of
1655   itself), or when the server is under attack by a client attempting to
1656   exploit security holes present in some servers using fixed-length
1657   buffers for reading or manipulating the Request-URI.
1661<section title="415 Unsupported Media Type" anchor="status.415">
1662  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1663  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1665   The server is refusing to service the request because the entity of
1666   the request is in a format not supported by the requested resource
1667   for the requested method.
1671<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1672  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1673  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1675   The request included a Range request-header field (&header-range;) and none of
1676   the range-specifier values in this field overlap the current extent
1677   of the selected resource.
1681<section title="417 Expectation Failed" anchor="status.417">
1682  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1683  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1685   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1686   could not be met by this server, or, if the server is a proxy,
1687   the server has unambiguous evidence that the request could not be met
1688   by the next-hop server.
1693<section title="Server Error 5xx" anchor="status.5xx">
1695   Response status codes beginning with the digit "5" indicate cases in
1696   which the server is aware that it has erred or is incapable of
1697   performing the request. Except when responding to a HEAD request, the
1698   server &SHOULD; include an entity containing an explanation of the
1699   error situation, and whether it is a temporary or permanent
1700   condition. User agents &SHOULD; display any included entity to the
1701   user. These response codes are applicable to any request method.
1704<section title="500 Internal Server Error" anchor="status.500">
1705  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1706  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1708   The server encountered an unexpected condition which prevented it
1709   from fulfilling the request.
1713<section title="501 Not Implemented" anchor="status.501">
1714  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1715  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1717   The server does not support the functionality required to fulfill the
1718   request. This is the appropriate response when the server does not
1719   recognize the request method and is not capable of supporting it for
1720   any resource.
1724<section title="502 Bad Gateway" anchor="status.502">
1725  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1726  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1728   The server, while acting as a gateway or proxy, received an invalid
1729   response from the upstream server it accessed in attempting to
1730   fulfill the request.
1734<section title="503 Service Unavailable" anchor="status.503">
1735  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1736  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1738   The server is currently unable to handle the request due to a
1739   temporary overloading or maintenance of the server. The implication
1740   is that this is a temporary condition which will be alleviated after
1741   some delay. If known, the length of the delay &MAY; be indicated in a
1742   Retry-After header. If no Retry-After is given, the client &SHOULD;
1743   handle the response as it would for a 500 response.
1744  <list><t>
1745      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1746      server must use it when becoming overloaded. Some servers may wish
1747      to simply refuse the connection.
1748  </t></list>
1752<section title="504 Gateway Timeout" anchor="status.504">
1753  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1754  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1756   The server, while acting as a gateway or proxy, did not receive a
1757   timely response from the upstream server specified by the URI (e.g.
1758   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1759   to access in attempting to complete the request.
1760  <list><t>
1761      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1762      return 400 or 500 when DNS lookups time out.
1763  </t></list>
1767<section title="505 HTTP Version Not Supported" anchor="status.505">
1768  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1769  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1771   The server does not support, or refuses to support, the protocol
1772   version that was used in the request message. The server is
1773   indicating that it is unable or unwilling to complete the request
1774   using the same major version as the client, as described in &http-version;,
1775   other than with this error message. The response &SHOULD; contain
1776   an entity describing why that version is not supported and what other
1777   protocols are supported by that server.
1785<section title="Header Field Definitions" anchor="header.fields">
1787   This section defines the syntax and semantics of HTTP/1.1 header fields
1788   related to request and response semantics.
1791   For entity-header fields, both sender and recipient refer to either the
1792   client or the server, depending on who sends and who receives the entity.
1795<section title="Allow" anchor="header.allow">
1796  <iref primary="true" item="Allow header" x:for-anchor=""/>
1797  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1798  <x:anchor-alias value="Allow"/>
1799  <x:anchor-alias value="Allow-v"/>
1801      The response-header field "Allow" lists the set of methods advertised as
1802      supported by the resource identified by the Request-URI. The purpose of
1803      this field is strictly to inform the recipient of valid methods
1804      associated with the resource. An Allow header field &MUST; be
1805      present in a 405 (Method Not Allowed) response.
1807<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1808  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1809  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1812      Example of use:
1814<figure><artwork type="example">
1815  Allow: GET, HEAD, PUT
1818      The actual set of allowed methods is defined
1819      by the origin server at the time of each request.
1822      A proxy &MUST-NOT; modify the Allow header field even if it does not
1823      understand all the methods specified, since the user agent might
1824      have other means of communicating with the origin server.
1828<section title="Expect" anchor="header.expect">
1829  <iref primary="true" item="Expect header" x:for-anchor=""/>
1830  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1831  <x:anchor-alias value="Expect"/>
1832  <x:anchor-alias value="Expect-v"/>
1833  <x:anchor-alias value="expectation"/>
1834  <x:anchor-alias value="expectation-extension"/>
1835  <x:anchor-alias value="expect-params"/>
1837   The request-header field "Expect" is used to indicate that particular
1838   server behaviors are required by the client.
1840<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"/>
1841  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1842  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1844  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1845  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1846                           *<x:ref>expect-params</x:ref> ]
1847  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1850   A server that does not understand or is unable to comply with any of
1851   the expectation values in the Expect field of a request &MUST; respond
1852   with appropriate error status. The server &MUST; respond with a 417
1853   (Expectation Failed) status if any of the expectations cannot be met
1854   or, if there are other problems with the request, some other 4xx
1855   status.
1858   This header field is defined with extensible syntax to allow for
1859   future extensions. If a server receives a request containing an
1860   Expect field that includes an expectation-extension that it does not
1861   support, it &MUST; respond with a 417 (Expectation Failed) status.
1864   Comparison of expectation values is case-insensitive for unquoted
1865   tokens (including the 100-continue token), and is case-sensitive for
1866   quoted-string expectation-extensions.
1869   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1870   return a 417 (Expectation Failed) status if it receives a request
1871   with an expectation that it cannot meet. However, the Expect
1872   request-header itself is end-to-end; it &MUST; be forwarded if the
1873   request is forwarded.
1876   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1877   Expect header.
1880   See &use100; for the use of the 100 (Continue) status.
1884<section title="From" anchor="header.from">
1885  <iref primary="true" item="From header" x:for-anchor=""/>
1886  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1887  <x:anchor-alias value="From"/>
1888  <x:anchor-alias value="From-v"/>
1889  <x:anchor-alias value="mailbox"/>
1891   The request-header field "From", if given, &SHOULD; contain an Internet
1892   e-mail address for the human user who controls the requesting user
1893   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1894   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1896<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1897  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1898  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1900  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1903   An example is:
1905<figure><artwork type="example">
1906  From:
1909   This header field &MAY; be used for logging purposes and as a means for
1910   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1911   be used as an insecure form of access protection. The interpretation
1912   of this field is that the request is being performed on behalf of the
1913   person given, who accepts responsibility for the method performed. In
1914   particular, robot agents &SHOULD; include this header so that the
1915   person responsible for running the robot can be contacted if problems
1916   occur on the receiving end.
1919   The Internet e-mail address in this field &MAY; be separate from the
1920   Internet host which issued the request. For example, when a request
1921   is passed through a proxy the original issuer's address &SHOULD; be
1922   used.
1925   The client &SHOULD-NOT;  send the From header field without the user's
1926   approval, as it might conflict with the user's privacy interests or
1927   their site's security policy. It is strongly recommended that the
1928   user be able to disable, enable, and modify the value of this field
1929   at any time prior to a request.
1933<section title="Location" anchor="header.location">
1934  <iref primary="true" item="Location header" x:for-anchor=""/>
1935  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1936  <x:anchor-alias value="Location"/>
1937  <x:anchor-alias value="Location-v"/>
1939   The response-header field "Location" is used for the identification of a
1940   new resource or to redirect the recipient to a location other than the
1941   Request-URI for completion of the request.  For 201 (Created)
1942   responses, the Location is that of the new resource which was created
1943   by the request. For 3xx responses, the location &SHOULD; indicate the
1944   server's preferred URI for automatic redirection to the resource. The
1945   field value consists of a single absolute URI.
1947<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1948  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1949  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1952   An example is:
1954<figure><artwork type="example">
1955  Location:
1958  <list><t>
1959      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1960      from Location in that the Content-Location identifies the original
1961      location of the entity enclosed in the response. It is therefore
1962      possible for a response to contain header fields for both Location
1963      and Content-Location.
1964  </t></list>
1967   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1968   <list style="symbols">
1969      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1970      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1971      <t>With 305 Use Proxy.</t>
1972   </list>
1976<section title="Max-Forwards" anchor="header.max-forwards">
1977  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1978  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1979  <x:anchor-alias value="Max-Forwards"/>
1980  <x:anchor-alias value="Max-Forwards-v"/>
1982   The request-header "Max-Forwards" field provides a mechanism with the
1983   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1984   number of proxies or gateways that can forward the request to the
1985   next inbound server. This can be useful when the client is attempting
1986   to trace a request chain which appears to be failing or looping in
1987   mid-chain.
1989<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
1990  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
1991  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
1994   The Max-Forwards value is a decimal integer indicating the remaining
1995   number of times this request message may be forwarded.
1998   Each proxy or gateway recipient of a TRACE or OPTIONS request
1999   containing a Max-Forwards header field &MUST; check and update its
2000   value prior to forwarding the request. If the received value is zero
2001   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2002   respond as the final recipient. If the received Max-Forwards value is
2003   greater than zero, then the forwarded message &MUST; contain an updated
2004   Max-Forwards field with a value decremented by one (1).
2007   The Max-Forwards header field &MAY; be ignored for all other methods
2008   defined by this specification and for any extension methods for which
2009   it is not explicitly referred to as part of that method definition.
2013<section title="Referer" anchor="header.referer">
2014  <iref primary="true" item="Referer header" x:for-anchor=""/>
2015  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2016  <x:anchor-alias value="Referer"/>
2017  <x:anchor-alias value="Referer-v"/>
2019   The request-header field "Referer" [sic] allows the client to specify,
2020   for the server's benefit, the address (URI) of the resource from
2021   which the Request-URI was obtained (the "referrer", although the
2022   header field is misspelled.) The Referer request-header allows a
2023   server to generate lists of back-links to resources for interest,
2024   logging, optimized caching, etc. It also allows obsolete or mistyped
2025   links to be traced for maintenance. The Referer field &MUST-NOT; be
2026   sent if the Request-URI was obtained from a source that does not have
2027   its own URI, such as input from the user keyboard.
2029<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2030  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2031  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>relativeURI</x:ref>
2034   Example:
2036<figure><artwork type="example">
2037  Referer:
2040   If the field value is a relative URI, it &SHOULD; be interpreted
2041   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2042   <xref target=""/> for security considerations.
2046<section title="Retry-After" anchor="header.retry-after">
2047  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2048  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2049  <x:anchor-alias value="Retry-After"/>
2050  <x:anchor-alias value="Retry-After-v"/>
2052   The response-header "Retry-After" field can be used with a 503 (Service
2053   Unavailable) response to indicate how long the service is expected to
2054   be unavailable to the requesting client. This field &MAY; also be used
2055   with any 3xx (Redirection) response to indicate the minimum time the
2056   user-agent is asked wait before issuing the redirected request. The
2057   value of this field can be either an HTTP-date or an integer number
2058   of seconds (in decimal) after the time of the response.
2060<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2061  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2062  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2064<t anchor="">
2065  <x:anchor-alias value="delta-seconds"/>
2066   Time spans are non-negative decimal integers, representing time in
2067   seconds.
2069<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2070  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2073   Two examples of its use are
2075<figure><artwork type="example">
2076  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2077  Retry-After: 120
2080   In the latter example, the delay is 2 minutes.
2084<section title="Server" anchor="header.server">
2085  <iref primary="true" item="Server header" x:for-anchor=""/>
2086  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2087  <x:anchor-alias value="Server"/>
2088  <x:anchor-alias value="Server-v"/>
2090   The response-header field "Server" contains information about the
2091   software used by the origin server to handle the request. The field
2092   can contain multiple product tokens (&product-tokens;) and comments
2093   identifying the server and any significant subproducts. The product
2094   tokens are listed in order of their significance for identifying the
2095   application.
2097<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2098  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2099  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2100                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2103   Example:
2105<figure><artwork type="example">
2106  Server: CERN/3.0 libwww/2.17
2109   If the response is being forwarded through a proxy, the proxy
2110   application &MUST-NOT; modify the Server response-header. Instead, it
2111   &MUST; include a Via field (as described in &header-via;).
2112  <list><t>
2113      <x:h>Note:</x:h> Revealing the specific software version of the server might
2114      allow the server machine to become more vulnerable to attacks
2115      against software that is known to contain security holes. Server
2116      implementors are encouraged to make this field a configurable
2117      option.
2118  </t></list>
2122<section title="User-Agent" anchor="header.user-agent">
2123  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2124  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2125  <x:anchor-alias value="User-Agent"/>
2126  <x:anchor-alias value="User-Agent-v"/>
2128   The request-header field "User-Agent" contains information about the
2129   user agent originating the request. This is for statistical purposes,
2130   the tracing of protocol violations, and automated recognition of user
2131   agents for the sake of tailoring responses to avoid particular user
2132   agent limitations. User agents &SHOULD; include this field with
2133   requests. The field can contain multiple product tokens (&product-tokens;)
2134   and comments identifying the agent and any subproducts which form a
2135   significant part of the user agent. By convention, the product tokens
2136   are listed in order of their significance for identifying the
2137   application.
2139<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2140  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2141  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2142                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2145   Example:
2147<figure><artwork type="example">
2148  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2154<section title="IANA Considerations" anchor="IANA.considerations">
2156<section title="Method Registry" anchor="method.registration">
2158  The registration procedure for HTTP Methods is defined by
2159  <xref target="method.registry"/> of this document.
2162   The HTTP Method Registry located at <eref target=""/>
2163   should be populated with the registrations below:
2165<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2166<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2167   <ttcol>Method</ttcol>
2168   <ttcol>Safe</ttcol>
2169   <ttcol>Reference</ttcol>
2170   <c>CONNECT</c>
2171   <c>no</c>
2172   <c>
2173      <xref target="CONNECT"/>
2174   </c>
2175   <c>DELETE</c>
2176   <c>no</c>
2177   <c>
2178      <xref target="DELETE"/>
2179   </c>
2180   <c>GET</c>
2181   <c>yes</c>
2182   <c>
2183      <xref target="GET"/>
2184   </c>
2185   <c>HEAD</c>
2186   <c>yes</c>
2187   <c>
2188      <xref target="HEAD"/>
2189   </c>
2190   <c>OPTIONS</c>
2191   <c>yes</c>
2192   <c>
2193      <xref target="OPTIONS"/>
2194   </c>
2195   <c>POST</c>
2196   <c>no</c>
2197   <c>
2198      <xref target="POST"/>
2199   </c>
2200   <c>PUT</c>
2201   <c>no</c>
2202   <c>
2203      <xref target="PUT"/>
2204   </c>
2205   <c>TRACE</c>
2206   <c>yes</c>
2207   <c>
2208      <xref target="TRACE"/>
2209   </c>
2214<section title="Status Code Registry" anchor="status.code.registration">
2216   The registration procedure for HTTP Status Codes -- previously defined
2217   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2218   by <xref target="status.code.registry"/> of this document.
2221   The HTTP Status Code Registry located at <eref target=""/>
2222   should be updated with the registrations below:
2224<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2225<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2226   <ttcol>Value</ttcol>
2227   <ttcol>Description</ttcol>
2228   <ttcol>Reference</ttcol>
2229   <c>100</c>
2230   <c>Continue</c>
2231   <c>
2232      <xref target="status.100"/>
2233   </c>
2234   <c>101</c>
2235   <c>Switching Protocols</c>
2236   <c>
2237      <xref target="status.101"/>
2238   </c>
2239   <c>200</c>
2240   <c>OK</c>
2241   <c>
2242      <xref target="status.200"/>
2243   </c>
2244   <c>201</c>
2245   <c>Created</c>
2246   <c>
2247      <xref target="status.201"/>
2248   </c>
2249   <c>202</c>
2250   <c>Accepted</c>
2251   <c>
2252      <xref target="status.202"/>
2253   </c>
2254   <c>203</c>
2255   <c>Non-Authoritative Information</c>
2256   <c>
2257      <xref target="status.203"/>
2258   </c>
2259   <c>204</c>
2260   <c>No Content</c>
2261   <c>
2262      <xref target="status.204"/>
2263   </c>
2264   <c>205</c>
2265   <c>Reset Content</c>
2266   <c>
2267      <xref target="status.205"/>
2268   </c>
2269   <c>206</c>
2270   <c>Partial Content</c>
2271   <c>
2272      <xref target="status.206"/>
2273   </c>
2274   <c>300</c>
2275   <c>Multiple Choices</c>
2276   <c>
2277      <xref target="status.300"/>
2278   </c>
2279   <c>301</c>
2280   <c>Moved Permanently</c>
2281   <c>
2282      <xref target="status.301"/>
2283   </c>
2284   <c>302</c>
2285   <c>Found</c>
2286   <c>
2287      <xref target="status.302"/>
2288   </c>
2289   <c>303</c>
2290   <c>See Other</c>
2291   <c>
2292      <xref target="status.303"/>
2293   </c>
2294   <c>304</c>
2295   <c>Not Modified</c>
2296   <c>
2297      <xref target="status.304"/>
2298   </c>
2299   <c>305</c>
2300   <c>Use Proxy</c>
2301   <c>
2302      <xref target="status.305"/>
2303   </c>
2304   <c>306</c>
2305   <c>(Unused)</c>
2306   <c>
2307      <xref target="status.306"/>
2308   </c>
2309   <c>307</c>
2310   <c>Temporary Redirect</c>
2311   <c>
2312      <xref target="status.307"/>
2313   </c>
2314   <c>400</c>
2315   <c>Bad Request</c>
2316   <c>
2317      <xref target="status.400"/>
2318   </c>
2319   <c>401</c>
2320   <c>Unauthorized</c>
2321   <c>
2322      <xref target="status.401"/>
2323   </c>
2324   <c>402</c>
2325   <c>Payment Required</c>
2326   <c>
2327      <xref target="status.402"/>
2328   </c>
2329   <c>403</c>
2330   <c>Forbidden</c>
2331   <c>
2332      <xref target="status.403"/>
2333   </c>
2334   <c>404</c>
2335   <c>Not Found</c>
2336   <c>
2337      <xref target="status.404"/>
2338   </c>
2339   <c>405</c>
2340   <c>Method Not Allowed</c>
2341   <c>
2342      <xref target="status.405"/>
2343   </c>
2344   <c>406</c>
2345   <c>Not Acceptable</c>
2346   <c>
2347      <xref target="status.406"/>
2348   </c>
2349   <c>407</c>
2350   <c>Proxy Authentication Required</c>
2351   <c>
2352      <xref target="status.407"/>
2353   </c>
2354   <c>408</c>
2355   <c>Request Timeout</c>
2356   <c>
2357      <xref target="status.408"/>
2358   </c>
2359   <c>409</c>
2360   <c>Conflict</c>
2361   <c>
2362      <xref target="status.409"/>
2363   </c>
2364   <c>410</c>
2365   <c>Gone</c>
2366   <c>
2367      <xref target="status.410"/>
2368   </c>
2369   <c>411</c>
2370   <c>Length Required</c>
2371   <c>
2372      <xref target="status.411"/>
2373   </c>
2374   <c>412</c>
2375   <c>Precondition Failed</c>
2376   <c>
2377      <xref target="status.412"/>
2378   </c>
2379   <c>413</c>
2380   <c>Request Entity Too Large</c>
2381   <c>
2382      <xref target="status.413"/>
2383   </c>
2384   <c>414</c>
2385   <c>Request-URI Too Long</c>
2386   <c>
2387      <xref target="status.414"/>
2388   </c>
2389   <c>415</c>
2390   <c>Unsupported Media Type</c>
2391   <c>
2392      <xref target="status.415"/>
2393   </c>
2394   <c>416</c>
2395   <c>Requested Range Not Satisfiable</c>
2396   <c>
2397      <xref target="status.416"/>
2398   </c>
2399   <c>417</c>
2400   <c>Expectation Failed</c>
2401   <c>
2402      <xref target="status.417"/>
2403   </c>
2404   <c>500</c>
2405   <c>Internal Server Error</c>
2406   <c>
2407      <xref target="status.500"/>
2408   </c>
2409   <c>501</c>
2410   <c>Not Implemented</c>
2411   <c>
2412      <xref target="status.501"/>
2413   </c>
2414   <c>502</c>
2415   <c>Bad Gateway</c>
2416   <c>
2417      <xref target="status.502"/>
2418   </c>
2419   <c>503</c>
2420   <c>Service Unavailable</c>
2421   <c>
2422      <xref target="status.503"/>
2423   </c>
2424   <c>504</c>
2425   <c>Gateway Timeout</c>
2426   <c>
2427      <xref target="status.504"/>
2428   </c>
2429   <c>505</c>
2430   <c>HTTP Version Not Supported</c>
2431   <c>
2432      <xref target="status.505"/>
2433   </c>
2437<section title="Message Header Registration" anchor="message.header.registration">
2439   The Message Header Registry located at <eref target=""/> should be updated
2440   with the permanent registrations below (see <xref target="RFC3864"/>):
2442<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2443<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2444   <ttcol>Header Field Name</ttcol>
2445   <ttcol>Protocol</ttcol>
2446   <ttcol>Status</ttcol>
2447   <ttcol>Reference</ttcol>
2448   <c>Allow</c>
2449   <c>http</c>
2450   <c>standard</c>
2451   <c>
2452      <xref target="header.allow"/>
2453   </c>
2454   <c>Expect</c>
2455   <c>http</c>
2456   <c>standard</c>
2457   <c>
2458      <xref target="header.expect"/>
2459   </c>
2460   <c>From</c>
2461   <c>http</c>
2462   <c>standard</c>
2463   <c>
2464      <xref target="header.from"/>
2465   </c>
2466   <c>Location</c>
2467   <c>http</c>
2468   <c>standard</c>
2469   <c>
2470      <xref target="header.location"/>
2471   </c>
2472   <c>Max-Forwards</c>
2473   <c>http</c>
2474   <c>standard</c>
2475   <c>
2476      <xref target="header.max-forwards"/>
2477   </c>
2478   <c>Referer</c>
2479   <c>http</c>
2480   <c>standard</c>
2481   <c>
2482      <xref target="header.referer"/>
2483   </c>
2484   <c>Retry-After</c>
2485   <c>http</c>
2486   <c>standard</c>
2487   <c>
2488      <xref target="header.retry-after"/>
2489   </c>
2490   <c>Server</c>
2491   <c>http</c>
2492   <c>standard</c>
2493   <c>
2494      <xref target="header.server"/>
2495   </c>
2496   <c>User-Agent</c>
2497   <c>http</c>
2498   <c>standard</c>
2499   <c>
2500      <xref target="header.user-agent"/>
2501   </c>
2505   The change controller is: "IETF ( - Internet Engineering Task Force".
2510<section title="Security Considerations" anchor="security.considerations">
2512   This section is meant to inform application developers, information
2513   providers, and users of the security limitations in HTTP/1.1 as
2514   described by this document. The discussion does not include
2515   definitive solutions to the problems revealed, though it does make
2516   some suggestions for reducing security risks.
2519<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2521   Like any generic data transfer protocol, HTTP cannot regulate the
2522   content of the data that is transferred, nor is there any a priori
2523   method of determining the sensitivity of any particular piece of
2524   information within the context of any given request. Therefore,
2525   applications &SHOULD; supply as much control over this information as
2526   possible to the provider of that information. Four header fields are
2527   worth special mention in this context: Server, Via, Referer and From.
2530   Revealing the specific software version of the server might allow the
2531   server machine to become more vulnerable to attacks against software
2532   that is known to contain security holes. Implementors &SHOULD; make the
2533   Server header field a configurable option.
2536   Proxies which serve as a portal through a network firewall &SHOULD;
2537   take special precautions regarding the transfer of header information
2538   that identifies the hosts behind the firewall. In particular, they
2539   &SHOULD; remove, or replace with sanitized versions, any Via fields
2540   generated behind the firewall.
2543   The Referer header allows reading patterns to be studied and reverse
2544   links drawn. Although it can be very useful, its power can be abused
2545   if user details are not separated from the information contained in
2546   the Referer. Even when the personal information has been removed, the
2547   Referer header might indicate a private document's URI whose
2548   publication would be inappropriate.
2551   The information sent in the From field might conflict with the user's
2552   privacy interests or their site's security policy, and hence it
2553   &SHOULD-NOT;  be transmitted without the user being able to disable,
2554   enable, and modify the contents of the field. The user &MUST; be able
2555   to set the contents of this field within a user preference or
2556   application defaults configuration.
2559   We suggest, though do not require, that a convenient toggle interface
2560   be provided for the user to enable or disable the sending of From and
2561   Referer information.
2564   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2565   fields can sometimes be used to determine that a specific client or
2566   server have a particular security hole which might be exploited.
2567   Unfortunately, this same information is often used for other valuable
2568   purposes for which HTTP currently has no better mechanism.
2572<section title="Encoding Sensitive Information in URIs" anchor="">
2574   Because the source of a link might be private information or might
2575   reveal an otherwise private information source, it is strongly
2576   recommended that the user be able to select whether or not the
2577   Referer field is sent. For example, a browser client could have a
2578   toggle switch for browsing openly/anonymously, which would
2579   respectively enable/disable the sending of Referer and From
2580   information.
2583   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2584   HTTP request if the referring page was transferred with a secure
2585   protocol.
2588   Authors of services should not use
2589   GET-based forms for the submission of sensitive data because that
2590   data will be encoded in the Request-URI. Many existing
2591   servers, proxies, and user agents log or display the Request-URI in
2592   places where it might be visible to third parties. Such services can
2593   use POST-based form submission instead.
2597<section title="Location Headers and Spoofing" anchor="location.spoofing">
2599   If a single server supports multiple organizations that do not trust
2600   one another, then it &MUST; check the values of Location and Content-Location
2601   headers in responses that are generated under control of
2602   said organizations to make sure that they do not attempt to
2603   invalidate resources over which they have no authority.
2609<section title="Acknowledgments" anchor="ack">
2614<references title="Normative References">
2616<reference anchor="Part1">
2617  <front>
2618    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2619    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2620      <organization abbrev="Day Software">Day Software</organization>
2621      <address><email></email></address>
2622    </author>
2623    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2624      <organization>One Laptop per Child</organization>
2625      <address><email></email></address>
2626    </author>
2627    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2628      <organization abbrev="HP">Hewlett-Packard Company</organization>
2629      <address><email></email></address>
2630    </author>
2631    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2632      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2633      <address><email></email></address>
2634    </author>
2635    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2636      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2637      <address><email></email></address>
2638    </author>
2639    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2640      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2641      <address><email></email></address>
2642    </author>
2643    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2644      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2645      <address><email></email></address>
2646    </author>
2647    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2648      <organization abbrev="W3C">World Wide Web Consortium</organization>
2649      <address><email></email></address>
2650    </author>
2651    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2652      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2653      <address><email></email></address>
2654    </author>
2655    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2656  </front>
2657  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2658  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2661<reference anchor="Part3">
2662  <front>
2663    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2664    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2665      <organization abbrev="Day Software">Day Software</organization>
2666      <address><email></email></address>
2667    </author>
2668    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2669      <organization>One Laptop per Child</organization>
2670      <address><email></email></address>
2671    </author>
2672    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2673      <organization abbrev="HP">Hewlett-Packard Company</organization>
2674      <address><email></email></address>
2675    </author>
2676    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2677      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2678      <address><email></email></address>
2679    </author>
2680    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2681      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2682      <address><email></email></address>
2683    </author>
2684    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2685      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2686      <address><email></email></address>
2687    </author>
2688    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2689      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2690      <address><email></email></address>
2691    </author>
2692    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2693      <organization abbrev="W3C">World Wide Web Consortium</organization>
2694      <address><email></email></address>
2695    </author>
2696    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2697      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2698      <address><email></email></address>
2699    </author>
2700    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2701  </front>
2702  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2703  <x:source href="p3-payload.xml" basename="p3-payload"/>
2706<reference anchor="Part4">
2707  <front>
2708    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2709    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2710      <organization abbrev="Day Software">Day Software</organization>
2711      <address><email></email></address>
2712    </author>
2713    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2714      <organization>One Laptop per Child</organization>
2715      <address><email></email></address>
2716    </author>
2717    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2718      <organization abbrev="HP">Hewlett-Packard Company</organization>
2719      <address><email></email></address>
2720    </author>
2721    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2722      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2723      <address><email></email></address>
2724    </author>
2725    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2726      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2727      <address><email></email></address>
2728    </author>
2729    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2730      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2731      <address><email></email></address>
2732    </author>
2733    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2734      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2735      <address><email></email></address>
2736    </author>
2737    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2738      <organization abbrev="W3C">World Wide Web Consortium</organization>
2739      <address><email></email></address>
2740    </author>
2741    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2742      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2743      <address><email></email></address>
2744    </author>
2745    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2746  </front>
2747  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2748  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2751<reference anchor="Part5">
2752  <front>
2753    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2754    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2755      <organization abbrev="Day Software">Day Software</organization>
2756      <address><email></email></address>
2757    </author>
2758    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2759      <organization>One Laptop per Child</organization>
2760      <address><email></email></address>
2761    </author>
2762    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2763      <organization abbrev="HP">Hewlett-Packard Company</organization>
2764      <address><email></email></address>
2765    </author>
2766    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2767      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2768      <address><email></email></address>
2769    </author>
2770    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2771      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2772      <address><email></email></address>
2773    </author>
2774    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2775      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2776      <address><email></email></address>
2777    </author>
2778    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2779      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2780      <address><email></email></address>
2781    </author>
2782    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2783      <organization abbrev="W3C">World Wide Web Consortium</organization>
2784      <address><email></email></address>
2785    </author>
2786    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2787      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2788      <address><email></email></address>
2789    </author>
2790    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2791  </front>
2792  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2793  <x:source href="p5-range.xml" basename="p5-range"/>
2796<reference anchor="Part6">
2797  <front>
2798    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2799    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2800      <organization abbrev="Day Software">Day Software</organization>
2801      <address><email></email></address>
2802    </author>
2803    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2804      <organization>One Laptop per Child</organization>
2805      <address><email></email></address>
2806    </author>
2807    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2808      <organization abbrev="HP">Hewlett-Packard Company</organization>
2809      <address><email></email></address>
2810    </author>
2811    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2812      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2813      <address><email></email></address>
2814    </author>
2815    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2816      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2817      <address><email></email></address>
2818    </author>
2819    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2820      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2821      <address><email></email></address>
2822    </author>
2823    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2824      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2825      <address><email></email></address>
2826    </author>
2827    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2828      <organization abbrev="W3C">World Wide Web Consortium</organization>
2829      <address><email></email></address>
2830    </author>
2831    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2832      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2833      <address><email></email></address>
2834    </author>
2835    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2836  </front>
2837  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2838  <x:source href="p6-cache.xml" basename="p6-cache"/>
2841<reference anchor="Part7">
2842  <front>
2843    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2844    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2845      <organization abbrev="Day Software">Day Software</organization>
2846      <address><email></email></address>
2847    </author>
2848    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2849      <organization>One Laptop per Child</organization>
2850      <address><email></email></address>
2851    </author>
2852    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2853      <organization abbrev="HP">Hewlett-Packard Company</organization>
2854      <address><email></email></address>
2855    </author>
2856    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2857      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2858      <address><email></email></address>
2859    </author>
2860    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2861      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2862      <address><email></email></address>
2863    </author>
2864    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2865      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2866      <address><email></email></address>
2867    </author>
2868    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2869      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2870      <address><email></email></address>
2871    </author>
2872    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2873      <organization abbrev="W3C">World Wide Web Consortium</organization>
2874      <address><email></email></address>
2875    </author>
2876    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2877      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2878      <address><email></email></address>
2879    </author>
2880    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2881  </front>
2882  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2883  <x:source href="p7-auth.xml" basename="p7-auth"/>
2886<reference anchor="RFC2119">
2887  <front>
2888    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2889    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2890      <organization>Harvard University</organization>
2891      <address><email></email></address>
2892    </author>
2893    <date month="March" year="1997"/>
2894  </front>
2895  <seriesInfo name="BCP" value="14"/>
2896  <seriesInfo name="RFC" value="2119"/>
2901<references title="Informative References">
2903<reference anchor="RFC1945">
2904  <front>
2905    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2906    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2907      <organization>MIT, Laboratory for Computer Science</organization>
2908      <address><email></email></address>
2909    </author>
2910    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2911      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2912      <address><email></email></address>
2913    </author>
2914    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2915      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2916      <address><email></email></address>
2917    </author>
2918    <date month="May" year="1996"/>
2919  </front>
2920  <seriesInfo name="RFC" value="1945"/>
2923<reference anchor="RFC2068">
2924  <front>
2925    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2926    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2927      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2928      <address><email></email></address>
2929    </author>
2930    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2931      <organization>MIT Laboratory for Computer Science</organization>
2932      <address><email></email></address>
2933    </author>
2934    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2935      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2936      <address><email></email></address>
2937    </author>
2938    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2939      <organization>MIT Laboratory for Computer Science</organization>
2940      <address><email></email></address>
2941    </author>
2942    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2943      <organization>MIT Laboratory for Computer Science</organization>
2944      <address><email></email></address>
2945    </author>
2946    <date month="January" year="1997"/>
2947  </front>
2948  <seriesInfo name="RFC" value="2068"/>
2951<reference anchor="RFC2616">
2952  <front>
2953    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2954    <author initials="R." surname="Fielding" fullname="R. Fielding">
2955      <organization>University of California, Irvine</organization>
2956      <address><email></email></address>
2957    </author>
2958    <author initials="J." surname="Gettys" fullname="J. Gettys">
2959      <organization>W3C</organization>
2960      <address><email></email></address>
2961    </author>
2962    <author initials="J." surname="Mogul" fullname="J. Mogul">
2963      <organization>Compaq Computer Corporation</organization>
2964      <address><email></email></address>
2965    </author>
2966    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2967      <organization>MIT Laboratory for Computer Science</organization>
2968      <address><email></email></address>
2969    </author>
2970    <author initials="L." surname="Masinter" fullname="L. Masinter">
2971      <organization>Xerox Corporation</organization>
2972      <address><email></email></address>
2973    </author>
2974    <author initials="P." surname="Leach" fullname="P. Leach">
2975      <organization>Microsoft Corporation</organization>
2976      <address><email></email></address>
2977    </author>
2978    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2979      <organization>W3C</organization>
2980      <address><email></email></address>
2981    </author>
2982    <date month="June" year="1999"/>
2983  </front>
2984  <seriesInfo name="RFC" value="2616"/>
2987<reference anchor='RFC2817'>
2988  <front>
2989    <title>Upgrading to TLS Within HTTP/1.1</title>
2990    <author initials='R.' surname='Khare' fullname='R. Khare'>
2991      <organization>4K Associates / UC Irvine</organization>
2992      <address><email></email></address>
2993    </author>
2994    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2995      <organization>Agranat Systems, Inc.</organization>
2996      <address><email></email></address>
2997    </author>
2998    <date year='2000' month='May' />
2999  </front>
3000  <seriesInfo name='RFC' value='2817' />
3003<reference anchor='RFC3864'>
3004  <front>
3005    <title>Registration Procedures for Message Header Fields</title>
3006    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3007      <organization>Nine by Nine</organization>
3008      <address><email></email></address>
3009    </author>
3010    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3011      <organization>BEA Systems</organization>
3012      <address><email></email></address>
3013    </author>
3014    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3015      <organization>HP Labs</organization>
3016      <address><email></email></address>
3017    </author>
3018    <date year='2004' month='September' />
3019  </front>
3020  <seriesInfo name='BCP' value='90' />
3021  <seriesInfo name='RFC' value='3864' />
3024<reference anchor='RFC5226'>
3025  <front>
3026    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3027    <author initials='T.' surname='Narten' fullname='T. Narten'>
3028      <organization>IBM</organization>
3029      <address><email></email></address>
3030    </author>
3031    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3032      <organization>Google</organization>
3033      <address><email></email></address>
3034    </author>
3035    <date year='2008' month='May' />
3036  </front>
3037  <seriesInfo name='BCP' value='26' />
3038  <seriesInfo name='RFC' value='5226' />
3041<reference anchor="RFC5322">
3042  <front>
3043    <title>Internet Message Format</title>
3044    <author initials="P." surname="Resnick" fullname="P. Resnick">
3045      <organization>Qualcomm Incorporated</organization>
3046    </author>
3047    <date year="2008" month="October"/>
3048  </front>
3049  <seriesInfo name="RFC" value="5322"/>
3054<section title="Compatibility with Previous Versions" anchor="compatibility">
3055<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3057   Clarified which error code should be used for inbound server failures
3058   (e.g. DNS failures). (<xref target="status.504"/>).
3061   201 (Created) had a race that required an Etag be sent when a resource is
3062   first created. (<xref target="status.201"/>).
3065   Rewrite of message transmission requirements to make it much harder
3066   for implementors to get it wrong, as the consequences of errors here
3067   can have significant impact on the Internet, and to deal with the
3068   following problems:
3069  <list style="numbers">
3070      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3071         this was incorrectly placing a requirement on the behavior of
3072         an implementation of a future version of HTTP/1.x</t>
3074      <t>Made it clear that user-agents should retry requests, not
3075         "clients" in general.</t>
3077      <t>Converted requirements for clients to ignore unexpected 100
3078         (Continue) responses, and for proxies to forward 100 responses,
3079         into a general requirement for 1xx responses.</t>
3081      <t>Modified some TCP-specific language, to make it clearer that
3082         non-TCP transports are possible for HTTP.</t>
3084      <t>Require that the origin server &MUST-NOT; wait for the request
3085         body before it sends a required 100 (Continue) response.</t>
3087      <t>Allow, rather than require, a server to omit 100 (Continue) if
3088         it has already seen some of the request body.</t>
3090      <t>Allow servers to defend against denial-of-service attacks and
3091         broken clients.</t>
3092  </list>
3095   This change adds the Expect header and 417 status code.
3098   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3099   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3102   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
3103   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3107<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3109  This document takes over the Status Code Registry, previously defined
3110  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3111  (<xref target="status.code.registry"/>)
3114  Clarify definition of POST.
3115  (<xref target="POST"/>)
3118  Failed to consider that there are
3119  many other request methods that are safe to automatically redirect,
3120  and further that the user agent is able to make that determination
3121  based on the request method semantics.
3122  (Sections <xref format="counter" target="status.301"/>,
3123  <xref format="counter" target="status.302"/> and
3124  <xref format="counter" target="status.307"/>)
3127  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3128  It used to indicate that the requested resource must be accessed through the
3129  proxy given by the Location field. The Location field gave the URI of the
3130  proxy. The recipient was expected to repeat this single request via the proxy.
3131  (<xref target="status.305"/>)
3134  Reclassify Allow header as response header, removing the option to
3135  specify it in a PUT request.
3136  Relax the server requirement on the contents of the Allow header and
3137  remove requirement on clients to always trust the header value.
3138  (<xref target="header.allow"/>)
3141  Correct syntax of Location header to allow fragment,
3142  as referred symbol wasn't what was expected, and add some
3143  clarifications as to when it would not be appropriate.
3144  (<xref target="header.location"/>)
3147  In the description of the Server header, the Via field
3148  was described as a SHOULD. The requirement was and is stated
3149  correctly in the description of the Via header in &header-via;.
3150  (<xref target="header.server"/>)
3156<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3158<section title="Since RFC2616">
3160  Extracted relevant partitions from <xref target="RFC2616"/>.
3164<section title="Since draft-ietf-httpbis-p2-semantics-00">
3166  Closed issues:
3167  <list style="symbols">
3168    <t>
3169      <eref target=""/>:
3170      "Via is a MUST"
3171      (<eref target=""/>)
3172    </t>
3173    <t>
3174      <eref target=""/>:
3175      "Fragments allowed in Location"
3176      (<eref target=""/>)
3177    </t>
3178    <t>
3179      <eref target=""/>:
3180      "Safe Methods vs Redirection"
3181      (<eref target=""/>)
3182    </t>
3183    <t>
3184      <eref target=""/>:
3185      "Revise description of the POST method"
3186      (<eref target=""/>)
3187    </t>
3188    <t>
3189      <eref target=""/>:
3190      "Normative and Informative references"
3191    </t>
3192    <t>
3193      <eref target=""/>:
3194      "RFC2606 Compliance"
3195    </t>
3196    <t>
3197      <eref target=""/>:
3198      "Informative references"
3199    </t>
3200    <t>
3201      <eref target=""/>:
3202      "Redundant cross-references"
3203    </t>
3204  </list>
3207  Other changes:
3208  <list style="symbols">
3209    <t>
3210      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3211    </t>
3212  </list>
3216<section title="Since draft-ietf-httpbis-p2-semantics-01">
3218  Closed issues:
3219  <list style="symbols">
3220    <t>
3221      <eref target=""/>:
3222      "PUT side effects"
3223    </t>
3224    <t>
3225      <eref target=""/>:
3226      "Duplicate Host header requirements"
3227    </t>
3228  </list>
3231  Ongoing work on ABNF conversion (<eref target=""/>):
3232  <list style="symbols">
3233    <t>
3234      Move "Product Tokens" section (back) into Part 1, as "token" is used
3235      in the definition of the Upgrade header.
3236    </t>
3237    <t>
3238      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3239    </t>
3240    <t>
3241      Copy definition of delta-seconds from Part6 instead of referencing it.
3242    </t>
3243  </list>
3247<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3249  Closed issues:
3250  <list style="symbols">
3251    <t>
3252      <eref target=""/>:
3253      "Requiring Allow in 405 responses"
3254    </t>
3255    <t>
3256      <eref target=""/>:
3257      "Status Code Registry"
3258    </t>
3259    <t>
3260      <eref target=""/>:
3261      "Redirection vs. Location"
3262    </t>
3263    <t>
3264      <eref target=""/>:
3265      "Cacheability of 303 response"
3266    </t>
3267    <t>
3268      <eref target=""/>:
3269      "305 Use Proxy"
3270    </t>
3271    <t>
3272      <eref target=""/>:
3273      "Classification for Allow header"
3274    </t>
3275    <t>
3276      <eref target=""/>:
3277      "PUT - 'store under' vs 'store at'"
3278    </t>
3279  </list>
3282  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3283  <list style="symbols">
3284    <t>
3285      Reference RFC 3984, and update header registrations for headers defined
3286      in this document.
3287    </t>
3288  </list>
3291  Ongoing work on ABNF conversion (<eref target=""/>):
3292  <list style="symbols">
3293    <t>
3294      Replace string literals when the string really is case-sensitive (method).
3295    </t>
3296  </list>
3300<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3302  Closed issues:
3303  <list style="symbols">
3304    <t>
3305      <eref target=""/>:
3306      "OPTIONS request bodies"
3307    </t>
3308    <t>
3309      <eref target=""/>:
3310      "Description of CONNECT should refer to RFC2817"
3311    </t>
3312    <t>
3313      <eref target=""/>:
3314      "Location Content-Location reference request/response mixup"
3315    </t>
3316  </list>
3319  Ongoing work on Method Registry (<eref target=""/>):
3320  <list style="symbols">
3321    <t>
3322      Added initial proposal for registration process, plus initial
3323      content (non-HTTP/1.1 methods to be added by a separate specification).
3324    </t>
3325  </list>
3329<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3331  Closed issues:
3332  <list style="symbols">
3333    <t>
3334      <eref target=""/>:
3335      "Content-*"
3336    </t>
3337    <t>
3338      <eref target=""/>:
3339      "RFC 2822 is updated by RFC 5322"
3340    </t>
3341  </list>
3344  Ongoing work on ABNF conversion (<eref target=""/>):
3345  <list style="symbols">
3346    <t>
3347      Use "/" instead of "|" for alternatives.
3348    </t>
3349    <t>
3350      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3351      whitespace ("OWS") and required whitespace ("RWS").
3352    </t>
3353    <t>
3354      Rewrite ABNFs to spell out whitespace rules, factor out
3355      header value format definitions.
3356    </t>
3357  </list>
Note: See TracBrowser for help on using the repository browser.