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List of HTTP header fields

HTTP header fields are a list of strings sent and received by both the client program and server on every HTTP request and response. These headers are usually invisible to the end-user and are only processed or logged by the server and client applications. They define how information sent/received through the connection are encoded (as in Content-Encoding), the session verification and identification of the client (as in browser cookies, IP address, user-agent) or their anonymity thereof (VPN or proxy masking, user-agent spoofing), how the server should handle data (as in Do-Not-Track or Global Privacy Control), the age (the time it has resided in a shared cache) of the document being downloaded, amongst others.

General format

In HTTP version 1.x, header fields are transmitted after the request line (in case of a request HTTP message) or the response line (in case of a response HTTP message), which is the first line of a message. Header fields are colon-separated key-value pairs in clear-text string format, terminated by a carriage return (CR) and line feed (LF) character sequence. The end of the header section is indicated by an empty field line, resulting in the transmission of two consecutive CR-LF pairs. In the past, long lines could be folded into multiple lines; continuation lines are indicated by the presence of a space (SP) or horizontal tab (HT) as the first character on the next line. This folding was deprecated in RFC 7230.1

HTTP/22 and HTTP/3 instead use a binary protocol, where headers are encoded in a single HEADERS and zero or more CONTINUATION frames using HPACK3 (HTTP/2) or QPACK (HTTP/3), which both provide efficient header compression. The request or response line from HTTP/1 has also been replaced by several pseudo-header fields, each beginning with a colon (:).

Field names

A core set of fields is standardized by the Internet Engineering Task Force (IETF) in RFC 9110 and 9111. The Field Names, Header Fields and Repository of Provisional Registrations are maintained by the IANA. Additional field names and permissible values may be defined by each application.

Header field names are case-insensitive.4 This is in contrast to HTTP method names (GET, POST, etc.), which are case-sensitive.5

HTTP/2 makes some restrictions on specific header fields (see below).

Non-standard header fields were conventionally marked by prefixing the field name with X- but this convention was deprecated in June 2012 because of the inconveniences it caused when non-standard fields became standard.6 An earlier restriction on use of Downgraded- was lifted in March 2013.7

Field values

A few fields can contain comments (i.e. in User-Agent, Server, Via fields), which can be ignored by software.8

Many field values may contain a quality (q) key-value pair separated by equals sign, specifying a weight to use in content negotiation.9 For example, a browser may indicate that it accepts information in German or English, with German as preferred by setting the q value for de higher than that of en, as follows:

Accept-Language: de; q=1.0, en; q=0.5

Size limits

The standard imposes no limits to the size of each header field name or value, or to the number of fields. However, most servers, clients, and proxy software impose some limits for practical and security reasons. For example, the Apache 2.3 server by default limits the size of each field to 8,190 bytes, and there can be at most 100 header fields in a single request.10

Request fields

Standard request fields

NameDescriptionExampleStatusStandard
A-IMAcceptable instance-manipulations for the request.11A-IM: feedPermanentRFC 3229
AcceptMedia type(s) that is/are acceptable for the response. See Content negotiation.Accept: text/htmlPermanentRFC 9110
Accept-CharsetCharacter sets that are acceptable.Accept-Charset: utf-8PermanentRFC 9110
Accept-DatetimeAcceptable version in time.Accept-Datetime: Thu, 31 May 2007 20:35:00 GMTProvisionalRFC 7089
Accept-EncodingList of acceptable encodings. See HTTP compression.Accept-Encoding: gzip, deflatePermanentRFC 9110
Accept-LanguageList of acceptable human languages for response. See Content negotiation.Accept-Language: en-USPermanentRFC 9110
Access-Control-Request-Method,Access-Control-Request-Headers12Initiates a request for cross-origin resource sharing with Origin (below).Access-Control-Request-Method: GETPermanent: standard
AuthorizationAuthentication credentials for HTTP authentication.Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==PermanentRFC 9110
Cache-ControlUsed to specify directives that must be obeyed by all caching mechanisms along the request-response chain.Cache-Control: no-cachePermanentRFC 9111
ConnectionControl options for the current connection and list of hop-by-hop request fields.13

Must not be used with HTTP/2.14

Connection: keep-alive

Connection: Upgrade

PermanentRFC 9110
Content-EncodingThe type of encoding used on the data. See HTTP compression.Content-Encoding: gzipPermanentRFC 9110
Content-LengthThe length of the request body in octets (8-bit bytes).Content-Length: 348PermanentRFC 9110
Content-MD5A Base64-encoded binary MD5 sum of the content of the request body.Content-MD5: Q2hlY2sgSW50ZWdyaXR5IQ==Obsolete15RFC 1544, 1864, 4021
Content-TypeThe Media type of the body of the request (used with POST and PUT requests).Content-Type: application/x-www-form-urlencodedPermanentRFC 9110
CookieAn HTTP cookie previously sent by the server with Set-Cookie (below).Cookie: $Version=1; Skin=new;Permanent: standardRFC 2965, 6265
DateThe date and time at which the message was originated (in "HTTP-date" format as defined by RFC 9110: HTTP Semantics, section 5.6.7 "Date/Time Formats").Date: Tue, 15 Nov 1994 08:12:31 GMTPermanentRFC 9110
ExpectIndicates that particular server behaviors are required by the client.Expect: 100-continuePermanentRFC 9110
ForwardedDisclose original information of a client connecting to a web server through an HTTP proxy.16Forwarded: for=192.0.2.60;proto=http;by=203.0.113.43 Forwarded: for=192.0.2.43, for=198.51.100.17PermanentRFC 7239
FromThe email address of the user making the request.From: [email protected]PermanentRFC 9110
HostThe domain name of the server (for virtual hosting), and the TCP port number on which the server is listening. The port number may be omitted if the port is the standard port for the service requested.

Mandatory since HTTP/1.1.17If the request is generated directly in HTTP/2, it should not be used.18

Host: en.wikipedia.org:8080

Host: en.wikipedia.org

PermanentRFC 9110, 9113
HTTP2-SettingsA request that upgrades from HTTP/1.1 to HTTP/2 MUST include exactly one HTTP2-Settings header field. The HTTP2-Settings header field is a connection-specific header field that includes parameters that govern the HTTP/2 connection, provided in anticipation of the server accepting the request to upgrade.1920HTTP2-Settings: token64ObsoleteRFC 7540, 9113
If-MatchOnly perform the action if the client supplied entity matches the same entity on the server. This is mainly for methods like PUT to only update a resource if it has not been modified since the user last updated it.If-Match: "737060cd8c284d8af7ad3082f209582d"PermanentRFC 9110
If-Modified-SinceAllows a 304 Not Modified to be returned if content is unchanged.If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMTPermanentRFC 9110
If-None-MatchAllows a 304 Not Modified to be returned if content is unchanged, see HTTP ETag.If-None-Match: "737060cd8c284d8af7ad3082f209582d"PermanentRFC 9110
If-RangeIf the entity is unchanged, send me the part(s) that I am missing; otherwise, send me the entire new entity.If-Range: "737060cd8c284d8af7ad3082f209582d"PermanentRFC 9110
If-Unmodified-SinceOnly send the response if the entity has not been modified since a specific time.If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMTPermanentRFC 9110
Max-ForwardsLimit the number of times the message can be forwarded through proxies or gateways.Max-Forwards: 10PermanentRFC 9110
Origin21Initiates a request for cross-origin resource sharing (asks server for Access-Control-* response fields).Origin: http://www.example-social-network.comPermanent: standardRFC 6454
PragmaImplementation-specific fields that may have various effects anywhere along the request-response chain.Pragma: no-cacheOutdatedRFC 9111
PreferAllows client to request that certain behaviors be employed by a server while processing a request.Prefer: return=representationPermanentRFC 7240
Proxy-AuthorizationAuthorization credentials for connecting to a proxy.Proxy-Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==PermanentRFC 9110
RangeRequest only part of an entity. Bytes are numbered from 0. See Byte serving.Range: bytes=500-999PermanentRFC 9110
Referer [sic]This is the address of the previous web page from which a link to the currently requested page was followed. (The word "referrer" has been misspelled in the RFC as well as in most implementations to the point that it has become standard usage and is considered correct terminology.)Referer: http://en.wikipedia.org/wiki/Main_PagePermanentRFC 9110
TEThe transfer encodings the user agent is willing to accept: the same values as for the response header field Transfer-Encoding can be used, plus the "trailers" value (related to the "chunked" transfer method) to notify the server it expects to receive additional fields in the trailer after the last, zero-sized, chunk.

Only trailers is supported in HTTP/2.22

TE: trailers, deflatePermanentRFC 9110
TrailerThe Trailer general field value indicates that the given set of header fields is present in the trailer of a message encoded with chunked transfer coding.Trailer: Max-ForwardsPermanentRFC 9110
Transfer-EncodingThe form of encoding used to safely transfer the entity to the user. Currently defined methods are: chunked, compress, deflate, gzip, identity.

Must not be used with HTTP/2.23

Transfer-Encoding: chunkedPermanentRFC 9110
User-AgentThe user agent string of the user agent.User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/12.0PermanentRFC 9110
UpgradeAsk the server to upgrade to another protocol.

Must not be used in HTTP/2.24

Upgrade: h2c, HTTPS/1.3, IRC/6.9, RTA/x11, websocketPermanentRFC 9110
ViaInforms the server of proxies through which the request was sent.Via: 1.0 fred, 1.1 example.com (Apache/1.1)PermanentRFC 9110
WarningA general warning about possible problems with the entity body.Warning: 199 Miscellaneous warningObsolete25RFC 7234, 9111

Common non-standard request fields

Field nameDescriptionExample
Upgrade-Insecure-Requests26Tells a server which (presumably in the middle of a HTTP -> HTTPS migration) hosts mixed content that the client would prefer redirection to HTTPS and can handle Content-Security-Policy: upgrade-insecure-requestsUpgrade-Insecure-Requests: 1
X-Requested-WithMainly used to identify Ajax requests (most JavaScript frameworks send this field with value of XMLHttpRequest); also identifies Android apps using WebView27 X-Requested-With: XMLHttpRequest
DNT28Requests a web application to disable their tracking of a user. This is Mozilla's version of the X-Do-Not-Track header field (since Firefox 4.0 Beta 11). Safari and IE9 also have support for this field.29 On March 7, 2011, a draft proposal was submitted to IETF.30 The W3C Tracking Protection Working Group is producing a specification.31DNT: 1 (Do Not Track Enabled)

DNT: 0 (Do Not Track Disabled)

X-Forwarded-For32A de facto standard for identifying the originating IP address of a client connecting to a web server through an HTTP proxy or load balancer. Superseded by Forwarded header.X-Forwarded-For: client1, proxy1, proxy2

X-Forwarded-For: 129.78.138.66, 129.78.64.103

X-Forwarded-Host33A de facto standard for identifying the original host requested by the client in the Host HTTP request header, since the host name and/or port of the reverse proxy (load balancer) may differ from the origin server handling the request. Superseded by Forwarded header.X-Forwarded-Host: en.wikipedia.org:8080

X-Forwarded-Host: en.wikipedia.org

X-Forwarded-Proto34A de facto standard for identifying the originating protocol of an HTTP request, since a reverse proxy (or a load balancer) may communicate with a web server using HTTP even if the request to the reverse proxy is HTTPS. An alternative form of the header (X-ProxyUser-Ip) is used by Google clients talking to Google servers. Superseded by Forwarded header.X-Forwarded-Proto: https
Front-End-Https35Non-standard header field used by Microsoft applications and load-balancersFront-End-Https: on
X-Http-Method-Override36Requests a web application to override the method specified in the request (typically POST) with the method given in the header field (typically PUT or DELETE). This can be used when a user agent or firewall prevents PUT or DELETE methods from being sent directly (this is either a bug in the software component, which ought to be fixed, or an intentional configuration, in which case bypassing it may be the wrong thing to do).X-HTTP-Method-Override: DELETE
X-ATT-DeviceId37Allows easier parsing of the MakeModel/Firmware that is usually found in the User-Agent String of AT&T DevicesX-Att-Deviceid: GT-P7320/P7320XXLPG
X-Wap-Profile38Links to an XML file on the Internet with a full description and details about the device currently connecting. In the example to the right is an XML file for an AT&T Samsung Galaxy S2.x-wap-profile: http://wap.samsungmobile.com/uaprof/SGH-I777.xml
Proxy-Connection39Implemented as a misunderstanding of the HTTP specifications. Common because of mistakes in implementations of early HTTP versions. Has exactly the same functionality as standard Connection field.

Must not be used with HTTP/2.40

Proxy-Connection: keep-alive
X-UIDH414243Server-side deep packet inspection of a unique ID identifying customers of Verizon Wireless; also known as "perma-cookie" or "supercookie"X-UIDH: ...
X-Csrf-Token44Used to prevent cross-site request forgery. Alternative header names are: X-CSRFToken45 and X-XSRF-TOKEN46X-Csrf-Token: i8XNjC4b8KVok4uw5RftR38Wgp2BFwql
X-Request-ID,4748

X-Correlation-ID,49Correlation-ID50

Correlates HTTP requests between a client and server. Superseded by the traceparent header

51

X-Request-ID: f058ebd6-02f7-4d3f-942e-904344e8cde5
Save-Data52The Save-Data client hint request header available in Chrome, Opera, and Yandex browsers lets developers deliver lighter, faster applications to users who opt-in to data saving mode in their browser.Save-Data: on
Sec-GPC53The Sec-GPC (Global Privacy Control[broken anchor]) request header indicates whether the user consents to a website or service selling or sharing their personal information with third parties.Sec-GPC: 1

Response fields

Standard response fields

Field nameDescriptionExampleStatusStandard
Access-Control-Allow-Origin,Access-Control-Allow-Credentials,Access-Control-Expose-Headers,Access-Control-Max-Age,Access-Control-Allow-Methods,Access-Control-Allow-Headers54Specifying which web sites can participate in cross-origin resource sharingAccess-Control-Allow-Origin: *Permanent: standardRFC 7480
Accept-Patch55Specifies which patch document formats this server supportsAccept-Patch: text/example;charset=utf-8PermanentRFC 5789
Accept-RangesWhat partial content range types this server supports via byte servingAccept-Ranges: bytesPermanentRFC 9110
AgeThe age the object has been in a proxy cache in secondsAge: 12PermanentRFC 9111
AllowValid methods for a specified resource. To be used for a 405 Method not allowedAllow: GET, HEADPermanentRFC 9110
Alt-Svc56A server uses "Alt-Svc" header (meaning Alternative Services) to indicate that its resources can also be accessed at a different network location (host or port) or using a different protocol

When using HTTP/2, servers should instead send an ALTSVC frame.57

Alt-Svc: http/1.1="http2.example.com:8001"; ma=7200Permanent
Cache-ControlTells all caching mechanisms from server to client whether they may cache this object. It is measured in secondsCache-Control: max-age=3600PermanentRFC 9111
ConnectionControl options for the current connection and list of hop-by-hop response fields.58

Must not be used with HTTP/2.59

Connection: closePermanentRFC 9110
Content-LanguageThe natural language or languages of the intended audience for the enclosed content60Content-Language: idPermanentRFC 9110
Content-TypeThe MIME type of this contentContent-Type: text/html; charset=utf-8PermanentRFC 9110
LocationUsed in redirection, or when a new resource has been created.
  • Example 1: Location: http://www.w3.org/pub/WWW/People.html
  • Example 2: Location: /pub/WWW/People.html
PermanentRFC 9110
Proxy-AuthenticateRequest authentication to access the proxy.Proxy-Authenticate: BasicPermanentRFC 9110
Public-Key-Pins61HTTP Public Key Pinning, announces hash of website's authentic TLS certificatePublic-Key-Pins: max-age=2592000; pin-sha256="E9CZ9INDbd+2eRQozYqqbQ2yXLVKB9+xcprMF+44U1g=";PermanentRFC 7469
Retry-AfterIf an entity is temporarily unavailable, this instructs the client to try again later. Value could be a specified period of time (in seconds) or a HTTP-date.62
  • Example 1: Retry-After: 120
  • Example 2: Retry-After: Fri, 07 Nov 2014 23:59:59 GMT

Permanent

RFC 9110
ServerA name for the serverServer: Apache/2.4.1 (Unix)PermanentRFC 9110
WWW-AuthenticateIndicates the authentication scheme that should be used to access the requested entity.WWW-Authenticate: BasicPermanentRFC 9110

Common non-standard response fields

Field nameDescriptionExample
Content-Security-Policy,X-Content-Security-Policy,X-WebKit-CSP63Content Security Policy definition.X-WebKit-CSP: default-src 'self'
Expect-CT64Notify to prefer to enforce Certificate Transparency.Expect-CT: max-age=604800, enforce, report-uri="https://example.example/report"
NEL65Used to configure network request logging.NEL: { "report_to": "name_of_reporting_group", "max_age": 12345, "include_subdomains": false, "success_fraction": 0.0, "failure_fraction": 1.0 }
Permissions-Policy66To allow or disable different features or APIs of the browser.Permissions-Policy: fullscreen=(), camera=(), microphone=(), geolocation=(), interest-cohort=()67
RefreshTells the browser to refresh the page or redirect to a different URL, after a given number of seconds (0 meaning immediately); or when a new resource has been created. Header introduced by Netscape in 1995 and became a de facto standard supported by most web browsers. Eventually standardized in the HTML Living Standard in 2017.68Refresh: 5; url=http://www.w3.org/pub/WWW/People.html
Report-To69Instructs the user agent to store reporting endpoints for an origin.Report-To: { "group": "csp-endpoint", "max_age": 10886400, "endpoints": [ { "url": "https-url-of-site-which-collects-reports" } ] }
StatusCGI header field specifying the status of the HTTP response. Normal HTTP responses use a separate "Status-Line" instead, defined by RFC 9110.70Status: 200 OK
Timing-Allow-OriginThe Timing-Allow-Origin response header specifies origins that are allowed to see values of attributes retrieved via features of the Resource Timing API, which would otherwise be reported as zero due to cross-origin restrictions.71Timing-Allow-Origin: *

Timing-Allow-Origin: <origin>[, <origin>]*

X-Content-Duration72Provide the duration of the audio or video in seconds. Not supported by current browsers – the header was only supported by Gecko browsers, from which support was removed in 2015.73X-Content-Duration: 42.666
X-Content-Type-Options74The only defined value, "nosniff", prevents Internet Explorer from MIME-sniffing a response away from the declared content-type. This also applies to Google Chrome, when downloading extensions.75X-Content-Type-Options: nosniff76
X-Powered-By77Specifies the technology (e.g. ASP.NET, PHP, JBoss) supporting the web application (version details are often in X-Runtime, X-Version, or X-AspNet-Version)X-Powered-By: PHP/5.4.0
X-Redirect-By78Specifies the component that is responsible for a particular redirect.X-Redirect-By: WordPressX-Redirect-By: Polylang
X-Request-ID, X-Correlation-ID79Correlates HTTP requests between a client and server.X-Request-ID: f058ebd6-02f7-4d3f-942e-904344e8cde5
X-UA-Compatible80Recommends the preferred rendering engine (often a backward-compatibility mode) to use to display the content. Also used to activate Chrome Frame in Internet Explorer. In HTML Standard, only the IE=edge value is defined.81X-UA-Compatible: IE=edgeX-UA-Compatible: IE=EmulateIE7X-UA-Compatible: Chrome=1
X-XSS-Protection82Cross-site scripting (XSS) filterX-XSS-Protection: 1; mode=block

Effects of selected fields

Avoiding caching

If a web server responds with Cache-Control: no-cache then a web browser or other caching system (intermediate proxies) must not use the response to satisfy subsequent requests without first checking with the originating server (this process is called validation). This header field is part of HTTP version 1.1, and is ignored by some caches and browsers. It may be simulated by setting the Expires HTTP version 1.0 header field value to a time earlier than the response time. Notice that no-cache is not instructing the browser or proxies about whether or not to cache the content. It just tells the browser and proxies to validate the cache content with the server before using it (this is done by using If-Modified-Since, If-Unmodified-Since, If-Match, If-None-Match attributes mentioned above). Sending a no-cache value thus instructs a browser or proxy to not use the cache contents merely based on "freshness criteria" of the cache content. Another common way to prevent old content from being shown to the user without validation is Cache-Control: max-age=0. This instructs the user agent that the content is stale and should be validated before use.

The header field Cache-Control: no-store is intended to instruct a browser application to make a best effort not to write it to disk (i.e not to cache it).

The request that a resource should not be cached is no guarantee that it will not be written to disk. In particular, the HTTP/1.1 definition draws a distinction between history stores and caches. If the user navigates back to a previous page a browser may still show you a page that has been stored on disk in the history store. This is correct behavior according to the specification. Many user agents show different behavior in loading pages from the history store or cache depending on whether the protocol is HTTP or HTTPS.

The Cache-Control: no-cache HTTP/1.1 header field is also intended for use in requests made by the client. It is a means for the browser to tell the server and any intermediate caches that it wants a fresh version of the resource. The Pragma: no-cache header field, defined in the HTTP/1.0 spec, has the same purpose. It, however, is only defined for the request header. Its meaning in a response header is not specified.83 The behavior of Pragma: no-cache in a response is implementation specific. While some user agents do pay attention to this field in responses,84 the HTTP/1.1 RFC specifically warns against relying on this behavior.

See also

As of this edit, this article uses content from "What is the X-REQUEST-ID http header?", authored by Stefan Kögl at Stack Exchange, which is licensed in a way that permits reuse under the Creative Commons Attribution-ShareAlike 3.0 Unported License, but not under the GFDL. All relevant terms must be followed.

As of this edit, this article uses content from "Why does ASP.NET framework add the 'X-Powered-By:ASP.NET' HTTP Header in responses?", authored by Adrian Grigore at Stack Exchange, which is licensed in a way that permits reuse under the Creative Commons Attribution-ShareAlike 3.0 Unported License, but not under the GFDL. All relevant terms must be followed.

References

  1. "Field Parsing". Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing. June 2014. sec. 3.2.4. doi:10.17487/RFC7230. RFC 7230. https://datatracker.ietf.org/doc/html/rfc7230#section-3.2.4 ↩

  2. HTTP/2. June 2022. doi:10.17487/RFC9113. RFC 9113. https://datatracker.ietf.org/doc/html/rfc9113 ↩

  3. Peon, R.; Ruellan, H. (May 2015). "HPACK: Header Compression for HTTP/2". IETF. doi:10.17487/RFC7541. Retrieved December 13, 2021. {{cite journal}}: Cite journal requires |journal= (help) https://tools.ietf.org/html/rfc7541 ↩

  4. "Field Names". HTTP Semantics. June 2022. sec. 5.1. doi:10.17487/RFC9110. RFC 9110. https://datatracker.ietf.org/doc/html/rfc9110#section-5.1 ↩

  5. "Methods: Overview". HTTP Semantics. June 2022. sec. 9.1. doi:10.17487/RFC9110. RFC 9110. https://datatracker.ietf.org/doc/html/rfc9110#section-9.1 ↩

  6. Internet Engineering Task Force (June 1, 2012). "RFC 6648". doi:10.17487/RFC6648. Retrieved November 12, 2012. {{cite journal}}: Cite journal requires |journal= (help) http://tools.ietf.org/html/rfc6648 ↩

  7. "Message Headers". Iana.org. June 11, 2014. Retrieved June 12, 2014. https://www.iana.org/assignments/message-headers/message-headers.xml ↩

  8. "Comments". HTTP Semantics. June 2022. sec. 5.6.5. doi:10.17487/RFC9110. RFC 9110. https://datatracker.ietf.org/doc/html/rfc9110#section-5.6.5 ↩

  9. "Quality Values". HTTP Semantics. June 2022. sec. 12.4.2. doi:10.17487/RFC9110. RFC 9110. https://datatracker.ietf.org/doc/html/rfc9110#section-12.4.2 ↩

  10. "core - Apache HTTP Server". Httpd.apache.org. Archived from the original on May 9, 2012. Retrieved March 13, 2012. https://web.archive.org/web/20120509104709/https://httpd.apache.org/docs/2.3/mod/core.html#limitrequestfieldsize ↩

  11. RFC 3229. doi:10.17487/RFC3229. https://datatracker.ietf.org/doc/html/rfc3229 ↩

  12. "Cross-Origin Resource Sharing". Retrieved July 24, 2017. https://www.w3.org/TR/cors/ ↩

  13. "Connection header". HTTP Semantics. June 2022. sec. 7.6.1. doi:10.17487/RFC9110. RFC 9110. https://datatracker.ietf.org/doc/html/rfc9110#section-7.6.1 ↩

  14. "Connection-Specific Header Fields". HTTP/2. June 2022. sec. 8.2.2. doi:10.17487/RFC9113. RFC 9113. https://datatracker.ietf.org/doc/html/rfc9113#section-8.2.2 ↩

  15. "Changes from RFC 2616". Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. June 2014. sec. B. doi:10.17487/RFC7231. RFC 7231. https://datatracker.ietf.org/doc/html/rfc7231#appendix-B ↩

  16. Petersson, A.; Nilsson, M. (June 2014). "Forwarded HTTP Extension: Introduction". IETF. doi:10.17487/RFC7239. Retrieved January 7, 2016. {{cite journal}}: Cite journal requires |journal= (help) http://tools.ietf.org/html/rfc7239#section-1 ↩

  17. "Host and :authority". HTTP Semantics. June 2022. sec. 7.2. doi:10.17487/RFC9110. RFC 9110. https://datatracker.ietf.org/doc/html/rfc9110#section-7.2 ↩

  18. "Request Pseudo-Header Fields". HTTP/2. June 2022. sec. 8.3.1. doi:10.17487/RFC9113. RFC 9113. https://datatracker.ietf.org/doc/html/rfc9113#section-8.3.1 ↩

  19. "Message Headers". www.iana.org. Retrieved November 26, 2018. https://www.iana.org/assignments/message-headers/message-headers.xml ↩

  20. "HTTP2-Settings Header Field". Hypertext Transfer Protocol Version 2 (HTTP/2). sec. 3.2.1. doi:10.17487/RFC7540. RFC 7540. https://datatracker.ietf.org/doc/html/rfc7540#section-3.2.1 ↩

  21. "Cross-Origin Resource Sharing". Retrieved July 24, 2017. https://www.w3.org/TR/cors/ ↩

  22. "Connection-Specific Header Fields". HTTP/2. June 2022. sec. 8.2.2. doi:10.17487/RFC9113. RFC 9113. https://datatracker.ietf.org/doc/html/rfc9113#section-8.2.2 ↩

  23. "Connection-Specific Header Fields". HTTP/2. June 2022. sec. 8.2.2. doi:10.17487/RFC9113. RFC 9113. https://datatracker.ietf.org/doc/html/rfc9113#section-8.2.2 ↩

  24. "Connection-Specific Header Fields". HTTP/2. June 2022. sec. 8.2.2. doi:10.17487/RFC9113. RFC 9113. https://datatracker.ietf.org/doc/html/rfc9113#section-8.2.2 ↩

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