HTTP Working Group R. Fielding, UC Irvine INTERNET-DRAFT H. Frystyk, MIT/LCS <draft-ietf-http-v11-spec-01.html> T. Berners-Lee, MIT/LCS Expires May 22, 1996 January 19, 1996
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<URL:http://www.ics.uci.edu/pub/ietf/http/>. General discussions about HTTP
and the applications which use HTTP should take place on the <www-talk@w3.org> mailing
list.
NOTE: This specification is for discussion purposes only. It is not claimed to represent the consensus of the HTTP working group, and contains a number of proposals that either have not been discussed or are controversial. The working group is discussing significant changes in many areas, including logic bags, support for caching, range retrieval, content negotiation, MIME compatibility, authentication, timing of the PUT operation.
HTTP has been in use by the World-Wide Web global information initiative since 1990. This specification defines the protocol referred to as "HTTP/1.1".
1. Introduction
1.1 Purpose
1.2 Requirements
1.3 Terminology
1.4 Overall Operation
2. Notational Conventions and Generic Grammar
2.1 Augmented BNF
2.2 Basic Rules
3. Protocol Parameters
3.1 HTTP Version
3.2 Uniform Resource Identifiers
3.2.1 General Syntax
3.2.2 http URL
3.3 Date/Time Formats
3.3.1 Full Date
3.3.2 Delta Seconds
3.4 Character Sets
3.5 Content Codings
3.6 Transfer Codings
3.7 Media Types
3.7.1 Canonicalization and Text Defaults
3.7.2 Multipart Types
3.8 Product Tokens
3.9 Quality Values
3.10 Language Tags
3.11 Logic Bags
4. HTTP Message
4.1 Message Types
4.2 Message Headers
4.3 General Header Fields
5. Request
5.1 Request-Line
5.1.1 Method
5.1.2 Request-URI
5.2 Request Header Fields
6. Response
6.1 Status-Line
6.1.1 Status Code and Reason Phrase
6.2 Response Header Fields
7. Entity
7.1 Entity Header Fields
7.2 Entity Body
7.2.1 Type
7.2.2 Length
8. Method Definitions
8.1 OPTIONS
8.2 GET
8.3 HEAD
8.4 POST
8.5 PUT
8.6 PATCH
8.7 COPY
8.8 MOVE
8.9 DELETE
8.10 LINK
8.11 UNLINK
8.12 TRACE
8.13 WRAPPED
9. Status Code Definitions
9.1 Informational 1xx
100 Continue
101 Switching Protocols
9.2 Successful 2xx
200 OK
201 Created
202 Accepted
203 Non-Authoritative Information
204 No Content
205 Reset Content
206 Partial Content
9.3 Redirection 3xx
300 Multiple Choices
301 Moved Permanently
302 Moved Temporarily
303 See Other
304 Not Modified
305 Use Proxy
9.4 Client Error 4xx
400 Bad Request
401 Unauthorized
402 Payment Required
403 Forbidden
404 Not Found
405 Method Not Allowed
406 None Acceptable
407 Proxy Authentication Required
408 Request Timeout
409 Conflict
410 Gone
411 Length Required
412 Unless True
9.5 Server Error 5xx
500 Internal Server Error
501 Not Implemented
502 Bad Gateway
503 Service Unavailable
504 Gateway Timeout
10. Header Field Definitions
10.1 Accept
10.2 Accept-Charset
10.3 Accept-Encoding
10.4 Accept-Language
10.5 Allow
10.6 Authorization
10.7 Base
10.8 Cache-Control
10.9 Connection
10.9.1 Persistent Connections
10.10 Content-Encoding
10.11 Content-Language
10.12 Content-Length
10.13 Content-MD5
10.14 Content-Range
10.15 Content-Type
10.16 Content-Version
10.17 Date
10.18 Derived-From
10.19 Expires
10.20 Forwarded
10.21 From
10.22 Host
10.23 If-Modified-Since
10.24 Keep-Alive
10.25 Last-Modified
10.26 Link
10.27 Location
10.28 MIME-Version
10.29 Pragma
10.30 Proxy-Authenticate
10.31 Proxy-Authorization
10.32 Public
10.33 Range
10.34 Referer
10.35 Refresh
10.36 Retry-After
10.37 Server
10.38 Title
10.39 Transfer Encoding
10.40 Unless
10.41 Upgrade
10.42 URI
10.43 User-Agent
10.44 WWW-Authenticate
11. Access Authentication
11.1 Basic Authentication Scheme
11.2 Digest Authentication Scheme
12. Content Negotiation
12.1 Preemptive Negotiation
13. Caching
14. Security Considerations
14.1 Authentication of Clients
14.2 Safe Methods
14.3 Abuse of Server Log Information
14.4 Transfer of Sensitive Information
15. Acknowledgments
16. References
17. Authors' Addresses
Appendix A. Internet Media Type message/http
Appendix B. Tolerant Applications
Appendix C. Relationship to MIME
C.1 Conversion to Canonical Form
C.1.1 Representation of Line Breaks
C.1.2 Default Character Set
C.2 Conversion of Date Formats
C.3 Introduction of Content-Encoding
C.4 No Content-Transfer-Encoding
C.5 Introduction of Transfer-Encoding
Appendix D. Changes from HTTP/1.0
This specification defines the protocol referred to as "HTTP/1.1". This protocol is backwards-compatible with HTTP/1.0, but includes more stringent requirements in order to ensure reliable implementation of its features.
Practical information systems require more functionality than simple retrieval, including search, front-end update, and annotation. HTTP allows an open-ended set of methods to be used to indicate the purpose of a request. It builds on the discipline of reference provided by the Uniform Resource Identifier (URI) [3], as a location (URL) [4] or name (URN) [20], for indicating the resource on which a method is to be applied. Messages are passed in a format similar to that used by Internet Mail [9] and the Multipurpose Internet Mail Extensions (MIME) [7].
HTTP is also used as a generic protocol for communication between user agents and proxies/gateways to other Internet protocols, such as SMTP [16], NNTP [13], FTP [18], Gopher [2], and WAIS [10], allowing basic hypermedia access to resources available from diverse applications and simplifying the implementation of user agents.
Most HTTP communication is initiated by a user agent and consists of a request to be applied to a resource on some origin server. In the simplest case, this may be accomplished via a single connection (v) between the user agent (UA) and the origin server (O).
request chain ------------------------>
UA -------------------v------------------- O
<----------------------- response chain
A more complicated situation occurs when one or more intermediaries are present in the
request/response chain. There are three common forms of intermediary: proxy, gateway, and
tunnel. A proxy is a forwarding agent, receiving requests for a URI in its absolute form,
rewriting all or parts of the message, and forwarding the reformatted request toward the server
identified by the URI. A gateway is a receiving agent, acting as a layer above some other
server(s) and, if necessary, translating the requests to the underlying server's protocol. A tunnel
acts as a relay point between two connections without changing the messages; tunnels are used
when the communication needs to pass through an intermediary (such as a firewall) even when
the intermediary cannot understand the contents of the messages.
request chain -------------------------------------->
UA -----v----- A -----v----- B -----v----- C -----v----- O
<------------------------------------- response chain
The figure above shows three intermediaries (A, B, and C) between the user agent and origin
server. A request or response message that travels the whole chain must pass through four
separate connections. This distinction is important because some HTTP communication
options may apply only to the connection with the nearest, non-tunnel neighbor, only to the
end-points of the chain, or to all connections along the chain. Although the diagram is linear,
each participant may be engaged in multiple, simultaneous communications. For example, B
may be receiving requests from many clients other than A, and/or forwarding requests to
servers other than C, at the same time that it is handling A's request.
Any party to the communication which is not acting as a tunnel may employ an internal cache for handling requests. The effect of a cache is that the request/response chain is shortened if one of the participants along the chain has a cached response applicable to that request. The following illustrates the resulting chain if B has a cached copy of an earlier response from O (via C) for a request which has not been cached by UA or A.
request chain ---------->
UA -----v----- A -----v----- B - - - - - - C - - - - - - O
<--------- response chain
Not all responses are cachable, and some requests may contain modifiers which place special
requirements on cache behavior. HTTP requirements for cache behavior and cachable
responses are defined in Section 13.
On the Internet, HTTP communication generally takes place over TCP/IP connections. The default port is TCP 80 [19], but other ports can be used. This does not preclude HTTP from being implemented on top of any other protocol on the Internet, or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used, and the mapping of the HTTP/1.1 request and response structures onto the transport data units of the protocol in question is outside the scope of this specification.
For most implementations, each connection is established by the client prior to the request and closed by the server after sending the response. However, this is not a feature of the protocol and is not required by this specification. Both clients and servers must be capable of handling cases where either party closes the connection prematurely, due to user action, automated time-out, or program failure. In any case, the closing of the connection by either or both parties always terminates the current request, regardless of its status.
name = definition
"<" and ">") and is
separated from its definition by the equal character "=". Whitespace is only significant in
that indentation of continuation lines is used to indicate a rule definition that spans more
than one line. Certain basic rules are in uppercase, such as SP,
LWS, HT, CRLF, DIGIT,
ALPHA, etc. Angle brackets are used within definitions whenever their presence will
facilitate discerning the use of rule names.
"literal"
rule1 | rule2
"I") are alternatives,
e.g., "yes | no" will accept yes or no.
(rule1 rule2)
(elem (foo | bar) elem)" allows the token sequences
"elem foo elem" and "elem bar elem".
*rule
"*" preceding an element indicates repetition.
The full form is "<n>*<m>element" indicating at
least <n> and at most <m>
occurrences of element. Default values are 0
and infinity so that "*(element)" allows any number,
including zero; "1*element" requires at least one;
and "1*2element" allows one or two.
[rule]
[foo bar]"
is equivalent to "*1(foo bar)".
rule
<n>(element)" is equivalent to
"<n>*<n>(element)"; that is, exactly
<n> occurrences of (element).
Thus 2DIGIT is a 2-digit number, and 3ALPHA
is a string of three alphabetic characters.
#rule
"#" is defined, similar to "*",
for defining lists of elements. The full form is
"<n>#<m>element" indicating at least
<n> and at most <m> elements,
each separated by one or more commas (",") and optional
linear whitespace (LWS). This makes the usual form of lists very easy;
a rule such as "( *LWS element *( *LWS "," *LWS element ))"
can be shown as "1#element". Wherever this construct is used,
null elements are allowed, but do not contribute to the count of elements
present. That is, "(element), , (element)" is permitted, but
counts as only two elements. Therefore, where at least one element is
required, at least one non-null element must be present. Default values
are 0 and infinity so that "#(element)"
allows any number, including zero; "1#element" requires
at least one; and "1#2element" allows one or two.
; comment
implied *LWS
LWS) can be included
between any two adjacent words (token or
quoted-string), and between adjacent tokens and delimiters
(tspecials), without changing the interpretation of a field.
At least one delimiter (tspecials) must exist between any
two tokens, since they would otherwise be interpreted as a single token.
However, applications should attempt to follow "common form" when
generating HTTP constructs, since there exist some implementations that
fail to accept anything beyond the common forms.
OCTET = <any 8-bit sequence of data>
CHAR = <any US-ASCII character (octets 0 - 127)>
UPALPHA = <any US-ASCII uppercase letter "A".."Z">
LOALPHA = <any US-ASCII lowercase letter "a".."z">
ALPHA = UPALPHA | LOALPHA
DIGIT = <any US-ASCII digit "0".."9">
CTL = <any US-ASCII control character
(octets 0 - 31) and DEL (127)>
CR = <US-ASCII CR, carriage return (13)>
LF = <US-ASCII LF, linefeed (10)>
SP = <US-ASCII SP, space (32)>
HT = <US-ASCII HT, horizontal-tab (9)>
<"> = <US-ASCII double-quote mark (34)>
HTTP/1.1 defines the octet sequence CR LF as the end-of-line marker for all protocol elements
except the Entity-Body (see Appendix B for tolerant applications). The end-of-line marker
within an Entity-Body is defined by its associated media type, as described in Section 3.7.
CRLF = CR LF
HTTP/1.1 headers can be folded onto multiple lines if the continuation line begins with a space
or horizontal tab. All linear whitespace, including folding, has the same semantics as SP.
LWS = [CRLF] 1*( SP | HT )
The TEXT rule is only used for descriptive field contents and values that are not intended to be
interpreted by the message parser. Words of *TEXT may contain octets from character sets other
than US-ASCII only when encoded according to the rules of RFC 1522 [14].
TEXT = <any OCTET except CTLs,
but including LWS>
Recipients of header field TEXT containing octets outside the US-ASCII character set range
may assume that they represent ISO-8859-1 characters if there is no other encoding indicated
by an RFC 1522 mechanism.
Hexadecimal numeric characters are used in several protocol elements.
HEX = "A" | "B" | "C" | "D" | "E" | "F"
| "a" | "b" | "c" | "d" | "e" | "f" | DIGIT
Many HTTP/1.1 header field values consist of words separated by LWS or special characters.
These special characters must be in a quoted string to be used within a parameter value.
word = token | quoted-string
token = 1*<any CHAR except CTLs or tspecials>
tspecials = "(" | ")" | "<" | ">" | "@"
| "," | ";" | ":" | "\" | <">
| "/" | "[" | "]" | "?" | "="
| "{" | "}" | SP | HT
Comments can be included in some HTTP header fields by surrounding the comment text with
parentheses. Comments are only allowed in fields containing "comment" as part of their field
value definition. In all other fields, parentheses are considered part of the field value.
comment = "(" *( ctext | comment ) ")"
ctext = <any TEXT excluding "(" and ")">
A string of text is parsed as a single word if it is quoted using double-quote marks.
quoted-string = ( <"> *(qdtext) <"> )
qdtext = <any CHAR except <"> and CTLs,
but including LWS>
The backslash character ("\") may be used as a single-character quoting mechanism only within
quoted-string and comment constructs.
quoted-pair = "\" CHAR
Braces are used to delimit an attribute-value bag, which may consist of a set, list, or recursively
defined tokens and quoted strings. The bag semantics are defined by its context and the bag
name, which may be a Uniform Resource Identifier (Section 3.2) in some fields.
bag = "{" bagname 1*LWS *bagitem "}"
bagname = token | URI
bagitem = bag | token | quoted-string
The version of an HTTP message is indicated by an HTTP-Version field in the first line of the
message. If the protocol version is not specified, the recipient must assume that the message is
in the simple HTTP/0.9 format [6].
HTTP-Version = "HTTP" "/" 1*DIGIT "." 1*DIGIT
Note that the major and minor numbers should be treated as separate integers and that each may
be incremented higher than a single digit. Thus, HTTP/2.4 is a lower version than HTTP/2.13,
which in turn is lower than HTTP/12.3. Leading zeros should be ignored by recipients and
never generated by senders.
Applications sending Full-Request or Full-Response messages, as defined by this specification,
must include an HTTP-Version of "HTTP/1.1". Use of this version number indicates that the
sending application is at least conditionally compliant with this specification.
HTTP/1.1 servers must:
HTTP/1.1 clients must:
URI = ( absoluteURI | relativeURI ) [ "#" fragment ]
absoluteURI = scheme ":" *( uchar | reserved )
relativeURI = net_path | abs_path | rel_path
net_path = "//" net_loc [ abs_path ]
abs_path = "/" rel_path
rel_path = [ path ] [ ";" params ] [ "?" query ]
path = fsegment *( "/" segment )
fsegment = 1*pchar
segment = *pchar
params = param *( ";" param )
param = *( pchar | "/" )
scheme = 1*( ALPHA | DIGIT | "+" | "-" | "." )
net_loc = *( pchar | ";" | "?" )
query = *( uchar | reserved )
fragment = *( uchar | reserved )
pchar = uchar | ":" | "@" | "&" | "="
uchar = unreserved | escape
unreserved = ALPHA | DIGIT | safe | extra | national
escape = "%" HEX HEX
reserved = ";" | "/" | "?" | ":" | "@" | "&" | "="
extra = "!" | "*" | "'" | "(" | ")" | ","
safe = "$" | "-" | "_" | "." | "+"
unsafe = CTL | SP | <"> | "#" | "%" | "<" | ">"
national = <any OCTET excluding ALPHA, DIGIT,
reserved, extra, safe, and unsafe>
For definitive information on URL syntax and semantics, see RFC 1738 [4] and
RFC 1808 [11]. The BNF above includes national characters not allowed in valid URLs as
specified by RFC 1738, since HTTP servers are not restricted in the set of unreserved characters
allowed to represent the rel_path part of addresses, and HTTP proxies may receive requests for
URIs not defined by RFC 1738.
http_URL = "http:" "//" host [ ":" port ] [ abs_path ]
host = <A legal Internet host domain name
or IP address (in dotted-decimal form),
as defined by Section 2.1 of RFC 1123>
port = *DIGIT
If the port is empty or not given, port 80 is assumed. The semantics are that the identified
resource is located at the server listening for TCP connections on that port of that host, and the
Request-URI for the resource is abs_path. If the abs_path is not present in the URL, it must be
given as "/" when used as a Request-URI for a resource (Section 5.1.2).
Note: Although the HTTP protocol is independent of the transport layer protocol, the http URL only identifies resources by their TCP location, and thus non-TCP resources must be identified by some other URI scheme.The canonical form for "http" URLs is obtained by converting any
UPALPHA characters in host
to their LOALPHA equivalent (hostnames are case-insensitive), eliding the [ ":" port ] if the port
is 80, and replacing an empty abs_path with "/".
Sun, 06 Nov 1994 08:49:37 GMT ; RFC 822, updated by RFC 1123
Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
Sun Nov 6 08:49:37 1994 ; ANSI C's asctime() format
The first format is preferred as an Internet standard and represents a fixed-length subset of that
defined by RFC 1123 [8] (an update to RFC 822 [9]). The second format is in common use, but
is based on the obsolete RFC 850 [12] date format and lacks a four-digit year. HTTP/1.1 clients
and servers that parse the date value must accept all three formats, though they must only
generate the RFC 1123 format for representing date/time stamps in HTTP message fields.
Note: Recipients of date values are encouraged to be robust in accepting date values that may have been generated by non-HTTP applications, as is sometimes the case when retrieving or posting messages via proxies/gateways to SMTP or NNTP.All HTTP date/time stamps must be represented in Universal Time (UT), also known as Greenwich Mean Time (GMT), without exception. This is indicated in the first two formats by the inclusion of "GMT" as the three-letter abbreviation for time zone, and should be assumed when reading the asctime format.
HTTP-date = rfc1123-date | rfc850-date | asctime-date
rfc1123-date = wkday "," SP date1 SP time SP "GMT"
rfc850-date = weekday "," SP date2 SP time SP "GMT"
asctime-date = wkday SP date3 SP time SP 4DIGIT
date1 = 2DIGIT SP month SP 4DIGIT
; day month year (e.g., 02 Jun 1982)
date2 = 2DIGIT "-" month "-" 2DIGIT
; day-month-year (e.g., 02-Jun-82)
date3 = month SP ( 2DIGIT | ( SP 1DIGIT ))
; month day (e.g., Jun 2)
time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
; 00:00:00 - 23:59:59
wkday = "Mon" | "Tue" | "Wed"
| "Thu" | "Fri" | "Sat" | "Sun"
weekday = "Monday" | "Tuesday" | "Wednesday"
| "Thursday" | "Friday" | "Saturday" | "Sunday"
month = "Jan" | "Feb" | "Mar" | "Apr"
| "May" | "Jun" | "Jul" | "Aug"
| "Sep" | "Oct" | "Nov" | "Dec"
Note: HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers are not required to use these formats for user presentation, request logging, etc.
delta-seconds = 1*DIGIT
The term "character set" is used in this document to refer to a method used with one or more tables to convert a sequence of octets into a sequence of characters. Note that unconditional conversion in the other direction is not required, in that not all characters may be available in a given character set and a character set may provide more than one sequence of octets to represent a particular character. This definition is intended to allow various kinds of character encodings, from simple single-table mappings such as US-ASCII to complex table switching methods such as those that use ISO 2022's techniques. However, the definition associated with a MIME character set name must fully specify the mapping to be performed from octets to characters. In particular, use of external profiling information to determine the exact mapping is not permitted.HTTP character sets are identified by case-insensitive tokens. The complete set of tokens are defined by the IANA Character Set registry [19]. However, because that registry does not define a single, consistent token for each character set, we define here the preferred names for those character sets most likely to be used with HTTP entities. These character sets include those registered by RFC 1521 [7] -- the US-ASCII [21] and ISO-8859 [22] character sets -- and other names specifically recommended for use within MIME charset parameters.
charset = "US-ASCII"
| "ISO-8859-1" | "ISO-8859-2" | "ISO-8859-3"
| "ISO-8859-4" | "ISO-8859-5" | "ISO-8859-6"
| "ISO-8859-7" | "ISO-8859-8" | "ISO-8859-9"
| "ISO-2022-JP" | "ISO-2022-JP-2" | "ISO-2022-KR"
| "UNICODE-1-1" | "UNICODE-1-1-UTF-7" | "UNICODE-1-1-UTF-8"
| token
Although HTTP allows an arbitrary token to be used as a charset value, any token that has a
predefined value within the IANA Character Set registry [19] must represent the character set
defined by that registry. Applications should limit their use of character sets to those defined by
the IANA registry.
Note: This use of the term "character set" is more commonly referred to as a "character encoding." However, since HTTP and MIME share the same registry, it is important that the terminology also be shared.
content-coding = "gzip" | "compress" | token
Note: For historical reasons, HTTP applications should consider "x-gzip" andAll
"x-compress" to be equivalent to "gzip" and "compress", respectively.
content-coding values are case-insensitive. HTTP/1.1 uses content-coding values in the
Accept-Encoding (Section 10.3) and Content-Encoding (Section 10.10) header fields. Although
the value describes the content-coding, what is more important is that it indicates what
decoding mechanism will be required to remove the encoding. Note that a single program may
be capable of decoding multiple content-coding formats. Two values are defined by this
specification:
Note: Use of program names for the identification of encoding formats is not desirable and should be discouraged for future encodings. Their use here is representative of historical practice, not good design.
transfer-coding = "chunked" | token
All transfer-coding values are case-insensitive. HTTP/1.1 uses transfer coding values in the
Transfer-Encoding header field (Section 10.39).
Transfer codings are analogous to the Content-Transfer-Encoding values of MIME [7], which were designed to enable safe transport of binary data over a 7-bit transport service. However, "safe transport" has a different focus for an 8bit-clean transfer protocol. In HTTP, the only unsafe characteristic of message bodies is the difficulty in determining the exact body length (Section 7.2.2), or the desire to encrypt data over a shared transport.
All HTTP/1.1 applications must be able to receive and decode the "chunked" transfer coding. The chunked encoding modifies the body of a message in order to transfer it as a series of chunks, each with its own size indicator, followed by an optional footer containing entity-header fields. This allows dynamically-produced content to be transferred along with the information necessary for the recipient to verify that it has received the full message.
Chunked-Body = *chunk
"0" CRLF
footer
CRLF
chunk = chunk-size CRLF
chunk-data CRLF
chunk-size = hex-no-zero *HEX
chunk-data = chunk-size(OCTET)
footer = *<Entity-Header, excluding Content-Length
and Transfer-Encoding>
hex-no-zero = <HEX excluding "0">
Note that the chunks are ended by a zero-sized chunk, followed by the footer and terminated
by an empty line. An example process for decoding a Chunked-Body is presented in
Appendix C.5.
media-type = type "/" subtype *( ";" parameter )
type = token
subtype = token
Parameters may follow the type/subtype in the form of attribute/value pairs.
parameter = attribute "=" value
attribute = token
value = token | quoted-string
The type, subtype, and parameter attribute names are case-insensitive. Parameter values may
or may not be case-sensitive, depending on the semantics of the parameter name. LWS should
not be generated between the type and subtype, nor between an attribute and its value.
If a given media-type value has been registered by the IANA, any use of that value must be
indicative of the registered data format. Although HTTP allows the use of non-registered media
types, such usage must not conflict with the IANA registry. Data providers are strongly
encouraged to register their media types with IANA via the procedures outlined in
RFC 1590 [17].
All media-type's registered by IANA must be preferred over extension tokens. However, HTTP
does not limit applications to the use of officially registered media types, nor does it encourage
the use of an "x-" prefix for unofficial types outside of explicitly short experimental use
between consenting applications.
Content-Encoding and/or Transfer-Encoding, the data must be in canonical
form prior to that encoding. However, HTTP modifies the canonical form requirements for
media of primary type "text" and for "application" types consisting of text-like records.
HTTP redefines the canonical form of text media to allow multiple octet sequences to indicate a text line break. In addition to the preferred form of CRLF, HTTP applications must accept a bare CR or LF alone as representing a single line break in text media. Furthermore, if the text media is represented in a character set which does not use octets 13 and 10 for CR and LF respectively, as is the case for some multi-byte character sets, HTTP allows the use of whatever octet sequence(s) is defined by that character set to represent the equivalent of CRLF, bare CR, and bare LF. It is assumed that any recipient capable of using such a character set will know the appropriate octet sequence for representing line breaks within that character set.
Note: This interpretation of line breaks applies only to the contents of an Entity-Body and only after any Transfer-Encoding and/or Content-Encoding has been removed. All other HTTP constructs use CRLF exclusively to indicate a line break. Content and transfer codings define their own line break requirements.A recipient of an HTTP text entity should translate the received entity line breaks to the local line break conventions before saving the entity external to the application and its cache; whether this translation takes place immediately upon receipt of the entity, or only when prompted by the user, is entirely up to the individual application.
HTTP also redefines the default character set for text media in an entity body. If a textual media
type defines a charset parameter with a registered default value of "US-ASCII", HTTP changes
the default to be "ISO-8859-1". Since the ISO-8859-1 [22] character set is a superset of
US-ASCII [21], this does not affect the interpretation of entity bodies which only contain octets
within the US-ASCII character set (0 - 127). The presence of a charset parameter value in a
Content-Type header field overrides the default.
It is recommended that the character set of an entity body be labelled as the lowest common denominator of the character codes used within a document, with the exception that no label is preferred over the labels US-ASCII or ISO-8859-1.
Entity-Body. All multipart types share a common syntax, as defined in
Section 7.2.1 of RFC 1521 [7], and must include a boundary parameter as part of the media
type value. The message body is itself a protocol element and must therefore use only CRLF to
represent line breaks between body-parts. Unlike in MIME, the epilogue of any multipart
message must be empty; HTTP applications must not transmit the epilogue even if the original
resource contains an epilogue.
In HTTP, multipart body-parts may contain header fields which are significant to the meaning of that part. A URI entity-header field (Section 10.42) should be included in the body-part for each enclosed entity that can be identified by a URI.
In general, an HTTP user agent should follow the same or similar behavior as a MIME user agent would upon receipt of a multipart type. The following subtypes have been defined:
Note: This document does not define what is meant by "simultaneous presentation". That is, HTTP does not provide any means of synchronization between the parts in messages of type "multipart/parallel".Other multipart subtypes may be registered by IANA [19] according to the procedures defined in RFC 1590 [17]. If an application receives an unrecognized multipart subtype, the application must treat it as being equivalent to "multipart/mixed".
product = token ["/" product-version]
product-version = token
Examples:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3
Server: Apache/0.8.4
Product tokens should be short and to the point -- use of them for advertizing or other
non-essential information is explicitly forbidden. Although any token character may appear in
a product-version, this token should only be used for a version identifier (i.e., successive versions
of the same product should only differ in the product-version portion of the product value).
qvalue = ( "0" [ "." 0*3DIGIT ] )
| ( "." 0*3DIGIT )
| ( "1" [ "." 0*3("0") ] )
"Quality values" is a slight misnomer, since these values actually measure relative degradation
in perceived quality. Thus, a value of "0.8" represents a 20% degradation from the optimum
rather than a statement of 80% quality.
The syntax and registry of HTTP language tags is the same as that defined by RFC 1766 [1]. In summary, a language tag is composed of 1 or more parts: A primary language tag and a possibly empty series of subtags:
language-tag = primary-tag *( "-" subtag )
primary-tag = 1*8ALPHA
subtag = 1*8ALPHA
Whitespace is not allowed within the tag and all tags are case-insensitive. The namespace of
language tags is administered by the IANA. Example tags include:
en, en-US, en-cockney, i-cherokee, x-pig-latin
where any two-letter primary-tag is an ISO 639 language abbreviation and any two-letter initial
subtag is an ISO 3166 country code.
In the context of the Accept-Language header (Section 10.4), a language tag is not to be interpreted as a single token, as per RFC 1766, but as a hierarchy. A server should consider that it has a match when a language tag received in an Accept-Language header matches the initial portion of the language tag of a document. An exact match should be preferred. This interpretation allows a browser to send, for example:
Accept-Language: en-US, en; ql=0.95
when the intent is to access, in order of preference, documents in US-English ("en-US"), 'plain'
or 'international' English ("en"), and any other variant of English (initial "en-").
Note: Using the language tag as a hierarchy does not imply that all languages with a common prefix will be understood by those fluent in one or more of those languages; it simply allows the user to request this commonality when it is true for that user.
bag
syntax. Logic bags are used by HTTP in the Unless (Section 10.40) header field as expressions
to be tested against the requested resource's header field metainformation.
logic-bag = "{" expression "}"
expression = ( log-op 1*logic-bag )
| ( rel-op 1*field-tuple )
| ( "def" 1*field-name )
log-op = "and" | "or" | "xor" | "not"
rel-op = "eq" | "ne" | "lt" | "le" | "ge" | "gt" | "in"
field-tuple = "{" field-name ( bag | token | quoted-string ) "}"
The recursive structure of a logic bag allows a complex expression tree to be formed by joining
together subexpressions with logical operators. Expressions with relational operators are used
to compare the requested resource's corresponding metainformation (header field values) to
those inside the expression field-tuples. For example,
{or {ne {Content-MD5 "Q2hlY2sgSW50ZWdyaXR5IQ=="}}
{ne {Content-Length 10036}}
{ne {Content-Version "12.4.8"}}
{gt {Last-Modified "Mon, 04 Dec 1995 01:23:45 GMT"}}}
The expression is evaluated recursively by depth-first traversal and bottom-up evaluation of the
subexpressions until a true or false value can be determined. Multiple operands to an operator
imply a conjunctive ("and") expression; e.g.,
{eq {A "a"} {B "b"} {C "c"}}
is equivalent to
{and {eq {A "a"}} {eq {B "b"}} {eq {C "c"}}}
Each expression is evaluated as defined by the operator:
field-tuple values exactly match the resource's corresponding field values.
field-tuple values do not match the resource's corresponding field values.
1*DIGIT) and lexical comparison (for all others).
Except for "ne", any comparison to a field not defined by the resource evaluates to false.
HTTP-message = Simple-Request ; HTTP/0.9 messages
| Simple-Response
| Full-Request ; HTTP/1.1 messages
| Full-Response
Full-Request and Full-Response use the generic
message format of RFC 822 [9] for transferring
entities. Both messages may include optional header fields (also known as "headers") and an
entity body. The entity body is separated from the headers by a null line (i.e., a line with nothing
preceding the CRLF).
Full-Request = Request-Line ; Section 5.1
*( General-Header ; Section 4.3
| Request-Header ; Section 5.2
| Entity-Header ) ; Section 7.1
CRLF
[ Entity-Body ] ; Section 7.2
Full-Response = Status-Line ; Section 6.1
*( General-Header ; Section 4.3
| Response-Header ; Section 6.2
| Entity-Header ) ; Section 7.1
CRLF
[ Entity-Body ] ; Section 7.2
Simple-Request and Simple-Response do not allow the use of any header information and are
limited to a single request method (GET).
Simple-Request = "GET" SP Request-URI CRLF
Simple-Response = [ Entity-Body ]
Use of the Simple-Request format is discouraged because it prevents the client from using
content negotiation and the server from identifying the media type of the returned entity.
General-Header (Section 4.3), Request-Header (Section 5.2),
Response-Header (Section 6.2), and Entity-Header (Section 7.1) fields, follow the same generic
format as that given in Section 3.1 of RFC 822 [9]. Each header field consists of a name
followed by a colon (":") and the field value. Field names are case-insensitive. The field value
may be preceded by any amount of LWS, though a single SP is preferred. Header fields can be
extended over multiple lines by preceding each extra line with at least one SP or HT.
HTTP-header = field-name ":" [ field-value ] CRLF
field-name = token
field-value = *( field-content | LWS )
field-content = <the OCTETs making up the field-value
and consisting of either *TEXT or combinations
of token, tspecials, and quoted-string>
The order in which header fields are received is not significant. However, it is "good practice"
to send General-Header fields first, followed by Request-Header or Response-Header fields prior
to the Entity-Header fields.
Multiple HTTP-header fields with the same field-name may be present in a message if and only
if the entire field-value for that header field is defined as a comma-separated list [i.e., #(values)].
It must be possible to combine the multiple header fields into one "field-name: field-value" pair,
without changing the semantics of the message, by appending each subsequent field-value to
the first, each separated by a comma.
General-Header = Cache-Control ; Section 10.8
| Connection ; Section 10.9
| Date ; Section 10.17
| Forwarded ; Section 10.20
| Keep-Alive ; Section 10.24
| MIME-Version ; Section 10.28
| Pragma ; Section 10.29
| Upgrade ; Section 10.41
General header field names can be extended reliably only in combination with a change in the
protocol version. However, new or experimental header fields may be given the semantics of
general header fields if all parties in the communication recognize them to be general header
fields. Unrecognized header fields are treated as Entity-Header fields.
Request = Simple-Request | Full-Request
Simple-Request = "GET" SP Request-URI CRLF
Full-Request = Request-Line ; Section 5.1
*( General-Header ; Section 4.3
| Request-Header ; Section 5.2
| Entity-Header ) ; Section 7.1
CRLF
[ Entity-Body ] ; Section 7.2
If an HTTP/1.1 server receives a Simple-Request, it must respond with an HTTP/0.9
Simple-Response. An HTTP/1.1 client must never generate a Simple-Request.
Request-Line begins with a method token, followed by the Request-URI and the protocol
version, and ending with CRLF. The elements are separated by SP characters. No CR or LF are
allowed except in the final CRLF sequence.
Request-Line = Method SP Request-URI SP HTTP-Version CRLF
Note that the difference between a Simple-Request and the Request-Line of a Full-Request is the
presence of the HTTP-Version field and the availability of methods other than GET.
Method token indicates the method to be performed on the resource identified by the
Request-URI. The method is case-sensitive.
Method = "OPTIONS" ; Section 8.1
| "GET" ; Section 8.2
| "HEAD" ; Section 8.3
| "POST" ; Section 8.4
| "PUT" ; Section 8.5
| "PATCH" ; Section 8.6
| "COPY" ; Section 8.7
| "MOVE" ; Section 8.8
| "DELETE" ; Section 8.9
| "LINK" ; Section 8.10
| "UNLINK" ; Section 8.11
| "TRACE" ; Section 8.12
| "WRAPPED" ; Section 8.13
| extension-method
extension-method = token
The list of methods acceptable by a specific resource can be specified in an Allow header field
(Section 10.5). However, the client is always notified through the return code of the response
whether a method is currently allowed on a specific resource, as this can change dynamically.
Servers should return the status code 405 (method not allowed) if the method is known by the
server but not allowed for the requested resource, and 501 (not implemented) if the method is
unrecognized or not implemented by the server. The list of methods known by a server can be
listed in a Public response header field (Section 10.32).
The methods GET and HEAD must be supported by all general-purpose servers. Servers which provide Last-Modified dates for resources must also support the conditional GET method. All other methods are optional; however, if the above methods are implemented, they must be implemented with the same semantics as those specified in Section 8.
Request-URI is a Uniform Resource Identifier (Section 3.2) and identifies the resource upon
which to apply the request.
Request-URI = "*" | absoluteURI | abs_path
The three options for Request-URI are dependent on the nature of the request. The asterisk "*"
means that the request does not apply to a particular resource, but to the server itself, and is
only allowed when the Method used does not necessarily apply to a resource. One example
would be
OPTIONS * HTTP/1.1
The absoluteURI form is only allowed when the request is being made to a proxy. The proxy is
requested to forward the request and return the response. If the request is GET or HEAD and a
prior response is cached, the proxy may use the cached message if it passes any restrictions in
the Cache-Control and Expires header fields. Note that the proxy may forward the request on to
another proxy or directly to the server specified by the absoluteURI. In order to avoid request
loops, a proxy must be able to recognize all of its server names, including any aliases, local
variations, and the numeric IP address. An example Request-Line would be:
GET http://www.w3.org/pub/WWW/TheProject.html HTTP/1.1
The most common form of Request-URI is that used to identify a resource on an origin server
or gateway. In this case, only the absolute path of the URI is transmitted (see Section 3.2.1,
abs_path). For example, a client wishing to retrieve the resource above directly from the origin
server would create a TCP connection to port 80 of the host "www.w3.org" and send the line:
GET /pub/WWW/TheProject.html HTTP/1.1
followed by the remainder of the Full-Request. Note that the absolute path cannot be empty; if
none is present in the original URI, it must be given as "/" (the server root).
If a proxy receives a request without any path in the Request-URI and the method used is capable
of supporting the asterisk form of request, then the last proxy on the request chain must forward
the request with "*" as the final Request-URI. For example, the request
OPTIONS http://www.ics.uci.edu:8001 HTTP/1.1
would be forwarded by the proxy as
OPTIONS * HTTP/1.1
after connecting to port 8001 of host "www.ics.uci.edu".
The Request-URI is transmitted as an encoded string, where some characters may be escaped using the "% hex hex" encoding defined by RFC 1738 [4]. The origin server must decode the Request-URI in order to properly interpret the request.
Request-Header = Accept ; Section 10.1
| Accept-Charset ; Section 10.2
| Accept-Encoding ; Section 10.3
| Accept-Language ; Section 10.4
| Authorization ; Section 10.6
| From ; Section 10.21
| Host ; Section 10.22
| If-Modified-Since ; Section 10.23
| Proxy-Authorization ; Section 10.31
| Range ; Section 10.33
| Referer ; Section 10.34
| Unless ; Section 10.40
| User-Agent ; Section 10.43
Request-Header field names can be extended reliably only in combination with a change in the
protocol version. However, new or experimental header fields may be given the semantics of
request header fields if all parties in the communication recognize them to be request header
fields. Unrecognized header fields are treated as Entity-Header fields.
Response = Simple-Response | Full-Response
Simple-Response = [ Entity-Body ]
Full-Response = Status-Line ; Section 6.1
*( General-Header ; Section 4.3
| Response-Header ; Section 6.2
| Entity-Header ) ; Section 7.1
CRLF
[ Entity-Body ] ; Section 7.2
A Simple-Response should only be sent in response to an HTTP/0.9 Simple-Request or if the
server only supports the more limited HTTP/0.9 protocol. If a client sends an HTTP/1.1
Full-Request and receives a response that does not begin with a
Status-Line, it should assume that
the response is a Simple-Response and parse it accordingly. Note that the Simple-Response
consists only of the entity body and is terminated by the server closing the connection.
Full-Response message is the
Status-Line, consisting of the protocol version
followed by a numeric status code and its associated textual phrase, with each element
separated by SP characters. No CR or LF
is allowed except in the final CRLF sequence.
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
Since a status line always begins with the protocol version and status code
"HTTP/" 1*DIGIT "." 1*DIGIT SP 3DIGIT SP
(e.g., "HTTP/1.1 200 "), the presence of that expression is sufficient to differentiate a
Full-Response from a Simple-Response.
Although the Simple-Response format may allow such
an expression to occur at the beginning of an entity body, and thus cause a misinterpretation of
the message if it was given in response to a Full-Request, most HTTP/0.9 servers are limited to
responses of type "text/html" and therefore would never generate such a response.
Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy
the request. The Reason-Phrase is intended to give a short
textual description of the Status-Code.
The Status-Code is intended for use by automata and the Reason-Phrase is intended for the
human user. The client is not required to examine or display the Reason-Phrase.
The first digit of the Status-Code defines the class of response. The last two digits do not have
any categorization role. There are 5 values for the first digit:
Reason-Phrase's, are presented below. The reason phrases listed here are only
recommended -- they may be replaced by local equivalents without affecting the protocol.
These codes are fully defined in Section 9.
Status-Code = "100" ; Continue
| "101" ; Switching Protocols
| "200" ; OK
| "201" ; Created
| "202" ; Accepted
| "203" ; Non-Authoritative Information
| "204" ; No Content
| "205" ; Reset Content
| "206" ; Partial Content
| "300" ; Multiple Choices
| "301" ; Moved Permanently
| "302" ; Moved Temporarily
| "303" ; See Other
| "304" ; Not Modified
| "305" ; Use Proxy
| "400" ; Bad Request
| "401" ; Unauthorized
| "402" ; Payment Required
| "403" ; Forbidden
| "404" ; Not Found
| "405" ; Method Not Allowed
| "406" ; None Acceptable
| "407" ; Proxy Authentication Required
| "408" ; Request Timeout
| "409" ; Conflict
| "410" ; Gone
| "411" ; Length Required
| "412" ; Unless True
| "500" ; Internal Server Error
| "501" ; Not Implemented
| "502" ; Bad Gateway
| "503" ; Service Unavailable
| "504" ; Gateway Timeout
| extension-code
extension-code = 3DIGIT
Reason-Phrase = *<TEXT, excluding CR, LF>
HTTP status codes are extensible. HTTP applications are not required to understand the
meaning of all registered status codes, though such understanding is obviously desirable.
However, applications must understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the x00 status code of that
class, with the exception that an unrecognized response must not be cached. For example, if an
unrecognized status code of 431 is received by the client, it can safely assume that there was
something wrong with its request and treat the response as if it had received a 400 status code.
In such cases, user agents should present to the user the entity returned with the response, since
that entity is likely to include human-readable information which will explain the unusual
status.
Status-Line. These header fields are not intended to give
information about an Entity-Body returned in the response, but about access to the resource or
the server itself.
Response-Header = Location ; Section 10.27
| Proxy-Authenticate ; Section 10.30
| Public ; Section 10.32
| Retry-After ; Section 10.36
| Server ; Section 10.37
| WWW-Authenticate ; Section 10.44
Response-Header field names can be extended reliably only in combination with a change in the
protocol version. However, new or experimental header fields may be given the semantics of
response header fields if all parties in the communication recognize them to be response header
fields. Unrecognized header fields are treated as Entity-Header fields.
Full-Request and Full-Response messages may transfer an entity within some requests and
responses. An entity consists of Entity-Header fields
and (usually) an Entity-Body. In this section,
both sender and recipient refer to either the client or the server, depending on who sends and
who receives the entity.
Entity-Header fields define optional metainformation about the Entity-Body or, if no body is
present, about the resource identified by the request.
Entity-Header = Allow ; Section 10.5
| Content-Encoding ; Section 10.10
| Content-Language ; Section 10.11
| Content-Length ; Section 10.12
| Content-MD5 ; Section 10.13
| Content-Range ; Section 10.14
| Content-Type ; Section 10.15
| Content-Version ; Section 10.16
| Derived-From ; Section 10.18
| Expires ; Section 10.19
| Last-Modified ; Section 10.25
| Link ; Section 10.26
| Title ; Section 10.38
| Transfer-Encoding ; Section 10.39
| URI-header ; Section 10.42
| extension-header
extension-header = HTTP-header
The extension-header mechanism allows additional Entity-Header fields to be defined without
changing the protocol, but these fields cannot be assumed to be recognizable by the recipient.
Unrecognized header fields should be ignored by the recipient and forwarded by proxies.
Entity-Header fields.
Entity-Body = *OCTET
An entity body is included with a request message only when the request method calls for one.
The presence of an entity body in a request is signaled by the inclusion of a Content-Length
and/or Content-Type header field in the request message headers.
For response messages, whether or not an entity body is included with a message is dependent
on both the request method and the response code. All responses to the HEAD request method
must not include a body, even though the presence of entity header fields may lead one to
believe they do. All 1xx (informational), 204 (no content), and 304 (not modified) responses
must not include a body. All other responses must include an entity body or a Content-Length
header field defined with a value of zero (0).
Content-Type, Content-Encoding, and Transfer-Encoding. These define a
three-layer, ordered encoding model:
entity-body :=
Transfer-Encoding( Content-Encoding( Content-Type( data ) ) )
The default for both encodings is none (i.e., the identity function). Content-Type specifies the
media type of the underlying data. Content-Encoding may be used to indicate any additional
content codings applied to the type, usually for the purpose of data compression, that are a
property of the resource requested. Transfer-Encoding may be used to indicate any additional
transfer codings applied by an application to ensure safe and proper transfer of the message.
Note that Transfer-Encoding is a property of the message, not of the resource.
Any HTTP/1.1 message containing an entity body should include a Content-Type header field
defining the media type of that body. If and only if
the media type is not given by a Content-Type
header, as is the case for Simple-Response messages, the recipient may attempt to guess the
media type via inspection of its content and/or the name extension(s) of the URL used to
identify the resource. If the media type remains unknown, the recipient should treat it as type
"application/octet-stream".
Content-Length header field is present, its value in bytes represents the
length of the entity body. Otherwise, the body length is determined by the Transfer-Encoding (if
the "chunked" transfer coding has been applied), by the Content-Type (for multipart types with
an explicit end-of-body delimiter), or by the server closing the connection.
Note: Any response message which must not include an entity body (such as the 1xx, 204, and 304 responses and any response to a HEAD request) is always terminated by the first empty line after the header fields, regardless of the entity header fields present in the message.Closing the connection cannot be used to indicate the end of a request body, since it leaves no possibility for the server to send back a response. For compatibility with HTTP/1.0 applications, HTTP/1.1 requests containing an entity body must include a valid
Content-Length
header field unless the server is known to be HTTP/1.1 compliant. HTTP/1.1 servers must
accept the "chunked" transfer coding (Section 3.6)
and multipart media types (Section 3.7.2),
thus allowing either mechanism to be used for a request when Content-Length is unknown.
If a request contains an entity body and Content-Length is not specified, the server should
respond with 400 (bad request) if it cannot determine the length of the request message's
content, or with 411 (length required) if it wishes to insist on receiving a valid Content-Length.
Messages must not include both a Content-Length header field and the "chunked" transfer
coding. If both are received, the Content-Length must be ignored.
When a Content-Length is given in a message where an entity body is allowed, its field value
must exactly match the number of OCTETs in the entity body. HTTP/1.1 user agents must notify
the user when an invalid length is received and detected.
The semantics of all methods may be affected by the presence of an Unless request header field,
as described in Section 10.40.
OPTIONS method represents a request for information about the communication options
available on the request/response chain identified by the Request-URI. This method allows the
client to determine the options and/or requirements associated with a resource, or the
capabilities of a server, without implying a resource action or initiating a resource retrieval.
Unless the server's response is an error, the response must not include entity information other
than what can be considered as communication options (e.g., Allow is appropriate, but
Content-Type is not) and must include a Content-Length with a value of zero (0). Responses to
this method are not cachable.
If the Request-URI is an asterisk ("*"), the OPTIONS
request is intended to apply to the server
as a whole. A 200 response should include any header fields which indicate optional features
implemented by the server (e.g., Public), including any extensions not defined by this
specification, in addition to any applicable general or response header fields. As described in
Section 5.1.2, an "OPTIONS *" request
can be applied through a proxy by specifying the
destination server in the Request-URI without any path information.
If the Request-URI is not an asterisk, the OPTIONS
request applies only to the options that are
available when communicating with that resource. A 200 response should include any header
fields which indicate optional features implemented by the server and applicable to that
resource (e.g., Allow), including any extensions not defined by this specification, in addition to
any applicable general or response header fields. If the OPTIONS request passes through a
proxy, the proxy must edit the response to exclude those options known to be unavailable
through that proxy.
GET method means retrieve whatever information (in the form of an entity) is identified by
the Request-URI. If the Request-URI refers to a data-producing process, it is the produced data
which shall be returned as the entity in the response and not the source text of the process,
unless that text happens to be the output of the process.
The semantics of the GET method change to a "conditional GET" if the request message
includes an If-Modified-Since header field.
A conditional GET method requests that the identified
resource be transferred only if it has been modified since the date given by the If-Modified-Since
header, as described in Section 10.23.
The conditional GET method is intended to reduce
unnecessary network usage by allowing cached entities to be refreshed without requiring
multiple requests or transferring data already held by the client.
The semantics of the GET method change to a "partial GET" if the request message includes a
Range header field. A partial GET requests that only part of the identified resource be
transferred, as described in Section 10.33.
The partial GET method is intended to reduce
unnecessary network usage by allowing partially-retrieved entities to be completed without
transferring data already held by the client.
The response to a GET request may be cachable if and only if it meets the requirements for
HTTP caching described in Section 13.
HEAD method is identical to GET except that
the server must not return any Entity-Body in
the response. The metainformation contained in the HTTP headers in response to a HEAD
request should be identical to the information sent in response to a GET request. This method
can be used for obtaining metainformation about the resource identified by the Request-URI
without transferring the Entity-Body itself. This method is often used for testing hypertext links
for validity, accessibility, and recent modification.
The response to a HEAD request may be cachable in the sense that the information contained in
the response may be used to update a previously cached entity from that resource. If the new
field values indicate that the cached entity differs from the current resource (as would be
indicated by a change in Content-Length, Content-MD5,
or Content-Version), then the cache must discard the cached entity.
There is no "conditional HEAD" or "partial HEAD" request analogous to those associated with
the GET method. If an If-Modified-Since and/or
Range header field is included with a HEAD request, they should be ignored.
POST method is used to request that the destination server accept the entity enclosed in the
request as a new subordinate of the resource identified by the Request-URI in the Request-Line.
POST is designed to allow a uniform method to cover the following functions:
Request-URI. The posted entity is subordinate to that URI in the same way
that a file is subordinate to a directory containing it, a news article is subordinate to a
newsgroup to which it is posted, or a record is subordinate to a database.
HTTP/1.1 allows for a two-phase process to occur in accepting and processing a POST request.
If the media type of the posted entity is not "application/x-www-form-urlencoded" [5], an
HTTP/1.1 client must pause between sending the message header fields (including the empty
line signifying the end of the headers) and sending the message body; the duration of the pause
is five (5) seconds or until a response is received from the server, whichever is shorter. If no
response is received during the pause period, or if the initial response is 100 (continue), the
client may continue sending the POST request. If the response indicates an error, the client must
discontinue the request and close the connection with the server after reading the response.
Upon receipt of a POST request, the server must examine the header fields and determine
whether or not the client should continue its request. If any of the header fields indicate the
request is insufficient or unacceptable to the server (i.e., will result in a 4xx or 5xx response),
or if the server can determine the response without reading the entity body (e.g., a 301 or 302
response due to an old Request-URI), the server must send that response immediately upon its
determination. If, on the other hand, the request appears (at least initially) to be acceptable and
the client has indicated HTTP/1.1 compliance, the server must transmit an interim 100 response
message after receiving the empty line terminating the request headers and continue processing
the request. After processing has finished, a final response message must be sent to indicate the
actual result of the request. A 100 response should not be sent in response to an HTTP/1.0
request except under experimental conditions, since an HTTP/1.0 client may mistake the 100
response for the final response.
For compatibility with HTTP/1.0 applications, all POST requests must include a valid
Content-Length header field unless the server is known to be HTTP/1.1 compliant. When
sending a POST request to an HTTP/1.1 server, a client must use at least one of: a valid
Content-Length, a multipart Content-Type, or the
"chunked" Transfer-Encoding. The server should
respond with a 400 (bad request) message if it cannot determine the length of the request
message's content, or with 411 (length required) if it wishes to insist on receiving a valid
Content-Length.
The client can suggest one or more URIs for the new resource by including a URI header field in the request. However, the server should treat those URIs as advisory and may store the entity under a different URI, additional URIs, or without any URI.
The client may apply relationships between the new resource and other existing resources by including Link header fields, as described in Section 10.26. The server may use the Link information to perform other operations as a result of the new resource being added. For example, lists and indexes might be updated. However, no mandatory operation is imposed on the origin server. The origin server may also generate its own or additional links to other resources.
A successful POST does not require that the entity be created as a resource on the origin server
or made accessible for future reference. That is, the action performed by the POST method
might not result in a resource that can be identified by a URI. In this case, either 200 (ok) or
204 (no content) is the appropriate response status, depending on whether or not the response
includes an entity that describes the result.
If a resource has been created on the origin server, the response should be 201 (created) and contain an entity (preferably of type "text/html") which describes the status of the request and refers to the new resource.
Responses to this method are not cachable. However, the 303 (see other) response can be used to direct the user agent to retrieve a cachable resource.
If the request passes through a cache and the Request-URI identifies a currently cached entity,
that entity must be removed from the cache. Responses to this method are not cachable.
The fundamental difference between the POST and PUT requests is reflected in the different
meaning of the Request-URI. The URI in a POST request identifies the resource that will handle
the enclosed entity as an appendage. That resource may be a data-accepting process, a gateway
to some other protocol, or a separate entity that accepts annotations. In contrast, the URI in a
PUT request identifies the entity enclosed with the request -- the user agent knows what URI
is intended and the server must not attempt to apply the request to some other resource. If the
server desires that the request be applied to a different URI, it must send a 301 (moved
permanently) response; the user agent may then make its own decision regarding whether or
not to redirect the request.
A single resource may be identified by many different URIs. For example, an article may have
a URI for identifying "the current version" which is separate from the URI identifying each
particular version. In this case, a PUT request on a general URI may result in several other URIs
being defined by the origin server. The user agent should be informed of these URIs via one or
more URI header fields in the response.
HTTP/1.1 allows for a two-phase process to occur in accepting and processing a PUT request.
An HTTP/1.1 client must pause between sending the message header fields (including the
empty line signifying the end of the headers) and sending the message body; the duration of the
pause is five (5) seconds or until a response is received from the server, whichever is shorter.
If no response is received during the pause period, or if the initial response is 100 (continue),
the client may continue sending the PUT request. If the response indicates an error, the client
must discontinue the request and close the connection with the server after reading the
response.
Upon receipt of a PUT request, the server must examine the header fields and determine
whether or not the client should continue its request. If any of the header fields indicate the
request is insufficient or unacceptable to the server (i.e., will result in a 4xx or 5xx response),
or if the server can determine the response without reading the entity body (e.g., a 301 or 302
response due to an old Request-URI), the server must send that response immediately upon its
determination. If, on the other hand, the request appears (at least initially) to be acceptable and
the client has indicated HTTP/1.1 compliance, the server must transmit an interim 100 response
message after receiving the empty line terminating the request headers and continue processing
the request. After processing has finished, a final response message must be sent to indicate the
actual result of the request. A 100 response should not be sent in response to an HTTP/1.0
request except under experimental conditions, since an HTTP/1.0 client may mistake the 100
response for the final response.
For compatibility with HTTP/1.0 applications, all PUT requests must include a valid
Content-Length header field unless the server is known to be HTTP/1.1 compliant. When
sending a PUT request to an HTTP/1.1 server, a client must use at least one of: a valid
Content-Length, a multipart Content-Type,
or the "chunked" Transfer-Encoding. The server should
respond with a 400 (bad request) message if it cannot determine the length of the request
message's content, or with 411 (length required) if it wishes to insist on receiving a valid
Content-Length.
The client can create or modify relationships between the enclosed entity and other existing resources by including Link header fields, as described in Section 10.26. As with POST, the server may use the Link information to perform other operations as a result of the request. However, no mandatory operation is imposed on the origin server. The origin server may generate its own or additional links to other resources.
The actual method for determining how the resource is placed, and what happens to its
predecessor, is defined entirely by the origin server. If version control is implemented by the
origin server, then Link relationships should be defined by the server to help identify and control
revisions to a resource. If the entity being PUT was derived from an existing resource which
included a Content-Version header field,
the new entity must include a Derived-From header field
corresponding to the value of the original Content-Version header field. Multiple Derived-From
values may be included if the entity was derived from multiple resources with Content-Version
information. Applications are encouraged to use these fields for constructing versioning
relationships and resolving version conflicts.
PATCH method is similar to PUT except that
the entity contains a list of differences between
the original version of the resource identified by the Request-URI and the desired content of the
resource after the PATCH action has been applied. The list of differences is in a format defined
by the media type of the entity (e.g., "application/diff") and must include sufficient information
to allow the server to recreate the changes necessary to convert the original version of the
resource to the desired version.
If the request passes through a cache and the Request-URI identifies a currently cached entity,
that entity must be removed from the cache. Responses to this method are not cachable.
HTTP/1.1 allows for a two-phase process to occur in accepting and processing a PATCH
request. An HTTP/1.1 client must pause between sending the message header fields (including
the empty line signifying the end of the headers) and sending the message body; the duration
of the pause is five (5) seconds or until a response is received from the server, whichever is
shorter. If no response is received during the pause period, or if the initial response is 100
(continue), the client may continue sending the PATCH request. If the response indicates an
error, the client must discontinue the request and close the connection with the server after
reading the response.
Upon receipt of a PATCH request, the server must examine the header fields and determine
whether or not the client should continue its request. If any of the header fields indicate the
request is insufficient or unacceptable to the server (i.e., will result in a 4xx or 5xx response),
or if the server can determine the response without reading the entity body (e.g., a 301 or 302
response due to an old Request-URI), the server must send that response immediately upon its
determination. If, on the other hand, the request appears (at least initially) to be acceptable and
the client has indicated HTTP/1.1 compliance, the server must transmit an interim 100 response
message after receiving the empty line terminating the request headers and continue processing
the request. After processing has finished, a final response message must be sent to indicate the
actual result of the request. A 100 response should not be sent in response to an HTTP/1.0
request except under experimental conditions, since an HTTP/1.0 client may mistake the 100
response for the final response.
For compatibility with HTTP/1.0 applications, all PATCH requests must include a valid
Content-Length header field unless the server is known to be HTTP/1.1 compliant. When
sending a PATCH request to an HTTP/1.1 server, a client must use at least one of: a valid
Content-Length, a multipart Content-Type,
or the "chunked" Transfer-Encoding. The server should
respond with a 400 (bad request) message if it cannot determine the length of the request
message's content, or with 411 (length required) if it wishes to insist on receiving a valid
Content-Length.
The client can create or modify relationships between the new resource and other existing resources by including Link header fields, as described in Section 10.26. As with POST, the server may use the Link information to perform other operations as a result of the request. However, no mandatory operation is imposed on the origin server. The origin server may generate its own or additional links to other resources.
The actual method for determining how the patched resource is placed, and what happens to its
predecessor, is defined entirely by the origin server. If version control is implemented by the
origin server, then Link relationships should be defined by the server to help identify and control
revisions to a resource. If the original version of the resource being patched included a
Content-Version header field, the request entity must include a Derived-From header field
corresponding to the value of the original Content-Version header field. Applications are
encouraged to use these fields for constructing versioning relationships and resolving version
conflicts.
COPY method requests that the resource identified by the Request-URI be copied to the
location(s) given in the URI header field of the request. Responses to this method are not
cachable.
MOVE method requests that the resource identified by the Request-URI be moved to the
location(s) given in the URI header field of the request. This method is equivalent to a COPY
immediately followed by a DELETE, but enables both to occur within a single transaction.
If the request passes through a cache and the Request-URI identifies a currently cached entity,
that entity must be removed from the cache. Responses to this method are not cachable.
A successful response should be 200 (ok) if the response includes an entity describing the status, 202 (accepted) if the action has not yet been enacted, or 204 (no content) if the response is OK but does not include an entity.
If the request passes through a cache and the Request-URI identifies a currently cached entity,
that entity must be removed from the cache. Responses to this method are not cachable.
If the request passes through a cache and the Request-URI identifies a currently cached entity,
that entity must be removed from the cache. Responses to this method are not cachable.
If the request passes through a cache and the Request-URI identifies a currently cached entity,
that entity must be removed from the cache. Responses to this method are not cachable.
Request-URI reflect whatever is
received back to the client as the entity body of the response. In this way, the client can see what
is being received at the other end of the request chain, and may use this data for testing or
diagnostic information.
If successful, the response should contain the entire, unedited request message in the entity body, with a Content-Type of "message/http", "application/http", or "text/plain". Responses to this method are not cachable.
Responses to this method are not cachable. Applications should not use this method for making requests that would normally be public and cachable.
The request entity must include at least one encapsulated message, with the media type
identifying the protocol of that message. For example, if the wrapped request is another HTTP
request message, then the media type must be either "message/http" (for a single message) or
"application/http" (for a request stream containing one or more requests), with any codings
identied by the Content-Encoding and Transfer-Encoding header fields.
HTTP/1.1 allows for a two-phase process to occur in accepting and processing a WRAPPED
request. An HTTP/1.1 client must pause between sending the message header fields (including
the empty line signifying the end of the headers) and sending the message body; the duration
of the pause is five (5) seconds or until a response is received from the server, whichever is
shorter. If no response is received during the pause period, or if the initial response is 100
(continue), the client may continue sending the WRAPPED request. If the response indicates an
error, the client must discontinue the request and close the connection with the server after
reading the response.
Upon receipt of a WRAPPED request, the server must examine the header fields and determine
whether or not the client should continue its request. If any of the header fields indicate the
request is insufficient or unacceptable to the server (i.e., will result in a 4xx or 5xx response),
or if the server can determine the response without reading the entity body (e.g., a 301 or 302
response due to an old Request-URI), the server must send that response immediately upon its
determination. If, on the other hand, the request appears (at least initially) to be acceptable and
the client has indicated HTTP/1.1 compliance, the server must transmit an interim 100 response
message after receiving the empty line terminating the request headers and continue processing
the request. After processing has finished, a final response message must be sent to indicate the
actual result of the request. A 100 response should not be sent in response to an HTTP/1.0
request except under experimental conditions, since an HTTP/1.0 client may mistake the 100
response for the final response.
For compatibility with HTTP/1.0 applications, all WRAPPED requests must include a valid
Content-Length header field unless the server is known to be HTTP/1.1 compliant. When
sending a WRAPPED request to an HTTP/1.1 server, a client must use at least one of: a valid
Content-Length, a multipart Content-Type,
or the "chunked" Transfer-Encoding. The server should
respond with a 400 (bad request) message if it cannot determine the length of the request
message's content, or with 411 (length required) if it wishes to insist on receiving a valid
Content-Length.
Status-Code is described below, including a description of which method(s) it can follow
and any metainformation required in the response.
Status-Line and
optional headers, and is terminated by an empty line. Since HTTP/1.0 did not define any 1xx
statu