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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

• Field names

• Field values

• Size limits

• Request fields

• Standard request fields

• Common non-standard request fields

• Response fields

• Standard response fields

• Common non-standard response fields

• Effects of selected fields

• Avoiding caching

• See also

• References

• External links

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.cite-ref-1[1]

HTTP/2cite-ref-rfc9113-2-0[2] and HTTP/3 instead use a binary protocol, where headers are encoded in a single HEADERS and zero or more CONTINUATION frames using HPACKcite-ref-rfc7541-3-0[3] (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 The request or response line from HTTP/1 has also been replaced by several pseudo-header fields, each beginning with a colon (:).

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.cite-ref-4[4] This is in contrast to HTTP method names (GET, POST, etc.), which are case-sensitive.cite-ref-5[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.cite-ref-6[6] An earlier restriction on use of Downgraded- was lifted in March 2013.cite-ref-7[7]

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

Many field values may contain a quality (q) key-value pair separated by equals sign, specifying a weight to use in content negotiation.cite-ref-9[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:

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.cite-ref-10[10]

| Name | Description |

|---|---|

| A-IM | Acceptable instance-manipulations for t… |

| Accept | Media type(s) that is/are acceptable fo… |

| Accept-Charset | Character sets that are acceptable. |

| Accept-Datetime | Acceptable version in time. |

| Accept-Encoding | List of acceptable encodings. See HTTP… |

| Accept-Language | List of acceptable human languages for… |

| Access-Control-Request-Method, Access-C… | Initiates a request for cross-origin re… |

| Authorization | Authentication credentials for HTTP aut… |

| Cache-Control | Used to specify directives that must be… |

| Connection | Control options for the current connect… |

| Content-Encoding | The type of encoding used on the data.… |

| Content-Length | The length of the request body in octet… |

| Content-MD5 | A Base64 -encoded binary MD5 sum of the… |

| Content-Type | The Media type of the body of the reque… |

| Cookie | An HTTP cookie previously sent by the s… |

| Date | The date and time at which the message… |

| Expect | Indicates that particular server behavi… |

| Forwarded | Disclose original information of a clie… |

| From | The email address of the user making th… |

| Host | The domain name of the server (for virt… |

| HTTP2-Settings | A request that upgrades from HTTP/1.1 t… |

| If-Match | Only perform the action if the client s… |

| If-Modified-Since | Allows a 304 Not Modified to be returne… |

| If-None-Match | Allows a 304 Not Modified to be returne… |

| If-Range | If the entity is unchanged, send me the… |

| If-Unmodified-Since | Only send the response if the entity ha… |

| Max-Forwards | Limit the number of times the message c… |

| Origin | Initiates a request for cross-origin re… |

| Pragma | Implementation-specific fields that may… |

| Prefer | Allows client to request that certain b… |

| Proxy-Authorization | Authorization credentials for connectin… |

| Range | Request only part of an entity. Bytes a… |

| Referer [ sic ] | This is the address of the previous web… |

| TE | The transfer encodings the user agent i… |

| Trailer | The Trailer general field value indicat… |

| Transfer-Encoding | The form of encoding used to safely tra… |

| User-Agent | The user agent string of the user agent. |

| Upgrade | Ask the server to upgrade to another pr… |

| Via | Informs the server of proxies through w… |

| Warning | A general warning about possible proble… |

| Name | Example |

|---|---|

| A-IM | A-IM: feed |

| Accept | Accept: text/html |

| Accept-Charset | Accept-Charset: utf-8 |

| Accept-Datetime | Accept-Datetime: Thu, 31 May 2007 20:35… |

| Accept-Encoding | Accept-Encoding: gzip, deflate |

| Accept-Language | Accept-Language: en-US |

| Access-Control-Request-Method, Access-C… | Access-Control-Request-Method: GET |

| Authorization | Authorization: Basic QWxhZGRpbjpvcGVuIH… |

| Cache-Control | Cache-Control: no-cache |

| Connection | Connection: keep-alive Connection: Upgr… |

| Content-Encoding | Content-Encoding: gzip |

| Content-Length | Content-Length: 348 |

| Content-MD5 | Content-MD5: Q2hlY2sgSW50ZWdyaXR5IQ== |

| Content-Type | Content-Type: application/x-www-form-ur… |

| Cookie | Cookie: $Version=1; Skin=new; |

| Date | Date: Tue, 15 Nov 1994 08:12:31 GMT |

| Expect | Expect: 100-continue |

| Forwarded | Forwarded: for=192.0.2.60;proto=http;by… |

| From | From: user@example.com |

| Host | Host: en.wikipedia.org:8080 Host: en.wi… |

| HTTP2-Settings | HTTP2-Settings: token64 |

| If-Match | If-Match: "737060cd8c284d8af7ad3082f209… |

| If-Modified-Since | If-Modified-Since: Sat, 29 Oct 1994 19:… |

| If-None-Match | If-None-Match: "737060cd8c284d8af7ad308… |

| If-Range | If-Range: "737060cd8c284d8af7ad3082f209… |

| If-Unmodified-Since | If-Unmodified-Since: Sat, 29 Oct 1994 1… |

| Max-Forwards | Max-Forwards: 10 |

| Origin | Origin: http://www.example-social-netwo… |

| Pragma | Pragma: no-cache |

| Prefer | Prefer: return=representation |

| Proxy-Authorization | Proxy-Authorization: Basic QWxhZGRpbjpv… |

| Range | Range: bytes=500-999 |

| Referer [ sic ] | Referer: http://en.wikipedia.org/wiki/M… |

| TE | TE: trailers, deflate |

| Trailer | Trailer: Max-Forwards |

| Transfer-Encoding | Transfer-Encoding: chunked |

| User-Agent | User-Agent: Mozilla/5.0 (X11; Linux x86… |

| Upgrade | Upgrade: h2c, HTTPS/1.3, IRC/6.9, RTA/x… |

| Via | Via: 1.0 fred, 1.1 example.com (Apache/… |

| Warning | Warning: 199 Miscellaneous warning |

| Name | Status | Standard |

|---|---|---|

| A-IM | Permanent | RFC 3229 |

| Accept | Permanent | RFC 9110 |

| Accept-Charset | Permanent | RFC 9110 |

| Accept-Datetime | Provisional | RFC 7089 |

| Accept-Encoding | Permanent | RFC 9110 |

| Accept-Language | Permanent | RFC 9110 |

| Access-Control-Request-Method, Access-C… | Permanent: standard | |

| Authorization | Permanent | RFC 9110 |

| Cache-Control | Permanent | RFC 9111 |

| Connection | Permanent | RFC 9110 |

| Content-Encoding | Permanent | RFC 9110 |

| Content-Length | Permanent | RFC 9110 |

| Content-MD5 | Obsolete | RFC 1544 , 1864 , 4021 |

| Content-Type | Permanent | RFC 9110 |

| Cookie | Permanent: standard | RFC 2965 , 6265 |

| Date | Permanent | RFC 9110 |

| Expect | Permanent | RFC 9110 |

| Forwarded | Permanent | RFC 7239 |

| From | Permanent | RFC 9110 |

| Host | Permanent | RFC 9110 , 9113 |

| HTTP2-Settings | Obsolete | RFC 7540 , 9113 |

| If-Match | Permanent | RFC 9110 |

| If-Modified-Since | Permanent | RFC 9110 |

| If-None-Match | Permanent | RFC 9110 |

| If-Range | Permanent | RFC 9110 |

| If-Unmodified-Since | Permanent | RFC 9110 |

| Max-Forwards | Permanent | RFC 9110 |

| Origin | Permanent: standard | RFC 6454 |

| Pragma | Outdated | RFC 9111 |

| Prefer | Permanent | RFC 7240 |

| Proxy-Authorization | Permanent | RFC 9110 |

| Range | Permanent | RFC 9110 |

| Referer [ sic ] | Permanent | RFC 9110 |

| TE | Permanent | RFC 9110 |

| Trailer | Permanent | RFC 9110 |

| Transfer-Encoding | Permanent | RFC 9110 |

| User-Agent | Permanent | RFC 9110 |

| Upgrade | Permanent | RFC 9110 |

| Via | Permanent | RFC 9110 |

| Warning | Obsolete | RFC 7234 , 9111 |

| Field name | Description |

|---|---|

| Upgrade-Insecure-Requests | Tells a server which (presumably in the… |

| X-Requested-With | Mainly used to identify Ajax requests (… |

| DNT | Requests a web application to disable t… |

| X-Forwarded-For | A de facto standard for identifying the… |

| X-Forwarded-Host | A de facto standard for identifying the… |

| X-Forwarded-Proto | A de facto standard for identifying the… |

| Front-End-Https | Non-standard header field used by Micro… |

| X-Http-Method-Override | Requests a web application to override… |

| X-ATT-DeviceId | Allows easier parsing of the MakeModel/… |

| X-Wap-Profile | Links to an XML file on the Internet wi… |

| Proxy-Connection | Implemented as a misunderstanding of th… |

| X-UIDH | Server-side deep packet inspection of a… |

| X-Csrf-Token | Used to prevent cross-site request forg… |

| X-Request-ID, X-Correlation-ID, Correla… | Correlates HTTP requests between a clie… |

| Save-Data | The Save-Data client hint request heade… |

| Sec-GPC | The Sec-GPC ( Global Privacy Control )… |

| Field name | Example |

|---|---|

| Upgrade-Insecure-Requests | Upgrade-Insecure-Requests: 1 |

| X-Requested-With | X-Requested-With: XMLHttpRequest |

| DNT | DNT: 1 (Do Not Track Enabled) DNT: 0 (D… |

| X-Forwarded-For | X-Forwarded-For: client1, proxy1, proxy… |

| X-Forwarded-Host | X-Forwarded-Host: en.wikipedia.org:8080… |

| X-Forwarded-Proto | X-Forwarded-Proto: https |

| Front-End-Https | Front-End-Https: on |

| X-Http-Method-Override | X-HTTP-Method-Override: DELETE |

| X-ATT-DeviceId | X-Att-Deviceid: GT-P7320/P7320XXLPG |

| X-Wap-Profile | x-wap-profile: http://wap.samsungmobile… |

| Proxy-Connection | Proxy-Connection: keep-alive |

| X-UIDH | X-UIDH: ... |

| X-Csrf-Token | X-Csrf-Token: i8XNjC4b8KVok4uw5RftR38Wg… |

| X-Request-ID, X-Correlation-ID, Correla… | X-Request-ID: f058ebd6-02f7-4d3f-942e-9… |

| Save-Data | Save-Data: on |

| Sec-GPC | Sec-GPC: 1 |

| Field name | Description |

|---|---|

| Accept-CH | Requests HTTP Client Hints |

| Access-Control-Allow-Origin, Access-Con… | Specifying which web sites can particip… |

| Accept-Patch | Specifies which patch document formats… |

| Accept-Ranges | What partial content range types this s… |

| Age | The age the object has been in a proxy… |

| Allow | Valid methods for a specified resource.… |

| Alt-Svc | A server uses "Alt-Svc" header (meaning… |

| Cache-Control | Tells all caching mechanisms from serve… |

| Connection | Control options for the current connect… |

| Content-Disposition | An opportunity to raise a "File Downloa… |

| Content-Encoding | The type of encoding used on the data.… |

| Content-Language | The natural language or languages of th… |

| Content-Length | The length of the response body in octe… |

| Content-Location | An alternate location for the returned… |

| Content-MD5 | A Base64 -encoded binary MD5 sum of the… |

| Content-Range | Where in a full body message this parti… |

| Content-Type | The MIME type of this content |

| Date | The date and time that the message was… |

| Delta-Base | Specifies the delta-encoding entity tag… |

| ETag | An identifier for a specific version of… |

| Expires | Gives the date/time after which the res… |

| IM | Instance-manipulations applied to the r… |

| Last-Modified | The last modified date for the requeste… |

| Link | Used to express a typed relationship wi… |

| Location | Used in redirection , or when a new res… |

| P3P | This field is supposed to set P3P polic… |

| Pragma | Implementation-specific fields that may… |

| Preference-Applied | Indicates which Prefer tokens were hono… |

| Proxy-Authenticate | Request authentication to access the pr… |

| Public-Key-Pins | HTTP Public Key Pinning , announces has… |

| Retry-After | If an entity is temporarily unavailable… |

| Server | A name for the server |

| Set-Cookie | An HTTP cookie |

| Strict-Transport-Security | A HSTS Policy informing the HTTP client… |

| Trailer | The Trailer general field value indicat… |

| Transfer-Encoding | The form of encoding used to safely tra… |

| Tk | Tracking Status header, value suggested… |

| Upgrade | Ask the client to upgrade to another pr… |

| Vary | Tells downstream proxies how to match f… |

| Via | Informs the client of proxies through w… |

| Warning | A general warning about possible proble… |

| WWW-Authenticate | Indicates the authentication scheme tha… |

| X-Frame-Options | Clickjacking protection: deny - no rend… |

| Field name | Example |

|---|---|

| Accept-CH | Accept-CH: UA, Platform |

| Access-Control-Allow-Origin, Access-Con… | Access-Control-Allow-Origin: * |

| Accept-Patch | Accept-Patch: text/example;charset=utf-8 |

| Accept-Ranges | Accept-Ranges: bytes |

| Age | Age: 12 |

| Allow | Allow: GET, HEAD |

| Alt-Svc | Alt-Svc: http/1.1="http2.example.com:80… |

| Cache-Control | Cache-Control: max-age=3600 |

| Connection | Connection: close |

| Content-Disposition | Content-Disposition: attachment; filena… |

| Content-Encoding | Content-Encoding: gzip |

| Content-Language | Content-Language: da |

| Content-Length | Content-Length: 348 |

| Content-Location | Content-Location: /index.htm |

| Content-MD5 | Content-MD5: Q2hlY2sgSW50ZWdyaXR5IQ== |

| Content-Range | Content-Range: bytes 21010-47021/47022 |

| Content-Type | Content-Type: text/html; charset=utf-8 |

| Date | Date: Tue, 15 Nov 1994 08:12:31 GMT |

| Delta-Base | Delta-Base: "abc" |

| ETag | ETag: "737060cd8c284d8af7ad3082f209582d" |

| Expires | Expires: Thu, 01 Dec 1994 16:00:00 GMT |

| IM | IM: feed |

| Last-Modified | Last-Modified: Tue, 15 Nov 1994 12:45:2… |

| Link | Link: </feed>; rel="alternate" |

| Location | Example 1: Location: http://www.w3.org/… |

| P3P | P3P: CP="This is not a P3P policy! See… |

| Pragma | Pragma: no-cache |

| Preference-Applied | Preference-Applied: return=representati… |

| Proxy-Authenticate | Proxy-Authenticate: Basic |

| Public-Key-Pins | Public-Key-Pins: max-age=2592000; pin-s… |

| Retry-After | Example 1: Retry-After: 120 Example 2:… |

| Server | Server: Apache/2.4.1 (Unix) |

| Set-Cookie | Set-Cookie: CookieName=CookieValue; Max… |

| Strict-Transport-Security | Strict-Transport-Security: max-age=1607… |

| Trailer | Trailer: Max-Forwards |

| Transfer-Encoding | Transfer-Encoding: chunked |

| Tk | Tk: ? |

| Upgrade | Upgrade: h2c, HTTPS/1.3, IRC/6.9, RTA/x… |

| Vary | Example 1: Vary: * Example 2: Vary: Acc… |

| Via | Via: 1.0 fred, 1.1 example.com (Apache/… |

| Warning | Warning: 199 Miscellaneous warning |

| WWW-Authenticate | WWW-Authenticate: Basic |

| X-Frame-Options | X-Frame-Options: deny |

| Field name | Status | Standard |

|---|---|---|

| Accept-CH | Experimental | RFC 8942 |

| Access-Control-Allow-Origin, Access-Con… | Permanent: standard | RFC 7480 |

| Accept-Patch | Permanent | RFC 5789 |

| Accept-Ranges | Permanent | RFC 9110 |

| Age | Permanent | RFC 9111 |

| Allow | Permanent | RFC 9110 |

| Alt-Svc | Permanent | |

| Cache-Control | Permanent | RFC 9111 |

| Connection | Permanent | RFC 9110 |

| Content-Disposition | Permanent | RFC 2616 , 4021 , 6266 |

| Content-Encoding | Permanent | RFC 9110 |

| Content-Language | Permanent | RFC 9110 |

| Content-Length | Permanent | RFC 9110 |

| Content-Location | Permanent | RFC 9110 |

| Content-MD5 | Obsolete | RFC 1544 , 1864 , 4021 |

| Content-Range | Permanent | RFC 9110 |

| Content-Type | Permanent | RFC 9110 |

| Date | Permanent | RFC 9110 |

| Delta-Base | Permanent | RFC 3229 |

| ETag | Permanent | RFC 9110 |

| Expires | Permanent: standard | RFC 9111 |

| IM | Permanent | RFC 3229 |

| Last-Modified | Permanent | RFC 9110 |

| Link | Permanent | RFC 8288 |

| Location | Permanent | RFC 9110 |

| P3P | Permanent | |

| Pragma | Permanent | RFC 9111 |

| Preference-Applied | Permanent | RFC 7240 |

| Proxy-Authenticate | Permanent | RFC 9110 |

| Public-Key-Pins | Permanent | RFC 7469 |

| Retry-After | Permanent | RFC 9110 |

| Server | Permanent | RFC 9110 |

| Set-Cookie | Permanent: standard | RFC 6265 |

| Strict-Transport-Security | Permanent: standard | |

| Trailer | Permanent | RFC 9110 |

| Transfer-Encoding | Permanent | RFC 9110 |

| Tk | Permanent | |

| Upgrade | Permanent | RFC 9110 |

| Vary | Permanent | RFC 9110 |

| Via | Permanent | RFC 9110 |

| Warning | Obsolete | RFC 7234 , 9111 |

| WWW-Authenticate | Permanent | RFC 9110 |

| X-Frame-Options | Obsolete | |

| Field name | Description |

|---|---|

| Content-Security-Policy, X-Content-Secu… | Content Security Policy definition. |

| Expect-CT | Notify to prefer to enforce Certificate… |

| NEL | Used to configure network request loggi… |

| Permissions-Policy | To allow or disable different features… |

| Refresh | Tells the browser to refresh the page o… |

| Report-To | Instructs the user agent to store repor… |

| Status | CGI header field specifying the status… |

| Timing-Allow-Origin | The Timing-Allow-Origin response header… |

| X-Content-Duration | Provide the duration of the audio or vi… |

| X-Content-Type-Options | The only defined value, "nosniff", prev… |

| X-Powered-By | Specifies the technology (e.g. ASP.NET,… |

| X-Redirect-By | Specifies the component that is respons… |

| X-Request-ID, X-Correlation-ID | Correlates HTTP requests between a clie… |

| X-UA-Compatible | Recommends the preferred rendering engi… |

| X-XSS-Protection | Cross-site scripting (XSS) filter |

| Field name | Example |

|---|---|

| Content-Security-Policy, X-Content-Secu… | X-WebKit-CSP: default-src 'self' |

| Expect-CT | Expect-CT: max-age=604800, enforce, rep… |

| NEL | NEL : { "report_to" : "name_of_reportin… |

| Permissions-Policy | Permissions-Policy: fullscreen=(), came… |

| Refresh | Refresh: 5; url= http://www.w3.org/pub/… |

| Report-To | Report-To : { "group" : "csp-endpoint"… |

| Status | Status: 200 OK |

| Timing-Allow-Origin | Timing-Allow-Origin: * Timing-Allow-Ori… |

| X-Content-Duration | X-Content-Duration: 42.666 |

| X-Content-Type-Options | X-Content-Type-Options: nosniff |

| X-Powered-By | X-Powered-By: PHP/5.4.0 |

| X-Redirect-By | X-Redirect-By: WordPress X-Redirect-By:… |

| X-Request-ID, X-Correlation-ID | X-Request-ID: f058ebd6-02f7-4d3f-942e-9… |

| X-UA-Compatible | X-UA-Compatible: IE=edge X-UA-Compatibl… |

| X-XSS-Protection | X-XSS-Protection: 1; mode=block |

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.cite-ref-79[77] The behavior of Pragma: no-cache in a response is implementation specific. While some user agents do pay attention to this field in responses,cite-ref-q234067-80-0[78] the HTTP/1.1 RFC specifically warns against relying on this behavior.

• HTTP header injection

• HTTP ETag

• List of HTTP status codes

cite-note-11. ↑ "Field Parsing". Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing. June 2014. sec. 3.2.4. doi:10.17487/RFC7230. RFC 7230.

cite-note-rfc9113-22. ↑ HTTP/2. June 2022. doi:10.17487/RFC9113. RFC 9113.

cite-note-rfc7541-33. ↑ citerefpeonruellan2015Peon, 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)

cite-note-44. ↑ "Field Names". HTTP Semantics. June 2022. sec. 5.1. doi:10.17487/RFC9110. RFC 9110.

cite-note-55. ↑ "Methods: Overview". HTTP Semantics. June 2022. sec. 9.1. doi:10.17487/RFC9110. RFC 9110.

cite-note-66. ↑ citerefinternet-engineering-task-force2012Internet Engineering Task Force (June 1, 2012). "RFC 6648". doi:10.17487/RFC6648. Retrieved November 12, 2012. {{cite journal}}: Cite journal requires |journal= (help)

cite-note-77. ↑ "Message Headers". Iana.org. June 11, 2014. Retrieved June 12, 2014.

cite-note-88. ↑ "Comments". HTTP Semantics. June 2022. sec. 5.6.5. doi:10.17487/RFC9110. RFC 9110.

cite-note-99. ↑ "Quality Values". HTTP Semantics. June 2022. sec. 12.4.2. doi:10.17487/RFC9110. RFC 9110.

cite-note-1010. ↑ "core - Apache HTTP Server". Httpd.apache.org. Archived from the original on May 9, 2012. Retrieved March 13, 2012.

cite-note-rfc3229-111. RFC 3229. doi:10.17487/RFC3229.

cite-note-cors-122. "Cross-Origin Resource Sharing". Retrieved July 24, 2017.

cite-note-rfc9110-connection-133. "Connection header". HTTP Semantics. June 2022. sec. 7.6.1. doi:10.17487/RFC9110. RFC 9110.

cite-note-rfc9113-connection-144. "Connection-Specific Header Fields". HTTP/2. June 2022. sec. 8.2.2. doi:10.17487/RFC9113. RFC 9113.

cite-note-7231-appendixb-155. "Changes from RFC 2616". Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. June 2014. sec. B. doi:10.17487/RFC7231. RFC 7231.

cite-note-166. citerefpeterssonnilsson2014Petersson, 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)

cite-note-177. "Host and :authority". HTTP Semantics. June 2022. sec. 7.2. doi:10.17487/RFC9110. RFC 9110.

cite-note-rfc9113-request-pseudo-header-fields-188. "Request Pseudo-Header Fields". HTTP/2. June 2022. sec. 8.3.1. doi:10.17487/RFC9113. RFC 9113.

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cite-note-2010. "HTTP2-Settings Header Field". Hypertext Transfer Protocol Version 2 (HTTP/2). sec. 3.2.1. doi:10.17487/RFC7540. RFC 7540.

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cite-note-4938. citerefdusseaultsnell2010Dusseault, L.; Snell, J. (2010). "RFC 5789". doi:10.17487/RFC5789. S2CID 42062521. Retrieved December 24, 2014. {{cite journal}}: Cite journal requires |journal= (help)

cite-note-5039. citerefnottinghammcmanusreschke2016Nottingham, M.; McManus, P.; Reschke, J. (April 2016). "HTTP Alternative Services". IETF. doi:10.17487/RFC7838. Retrieved April 19, 2016. {{cite journal}}: Cite journal requires |journal= (help)

cite-note-5140. citerefnottinghammcmanusreschke2016Nottingham, M.; McManus, P.; Reschke, J. (April 2016). "HTTP Alternative Services, section 3". IETF. doi:10.17487/RFC7838. Retrieved June 8, 2017. {{cite journal}}: Cite journal requires |journal= (help)

cite-note-5241. citerefreschke2011Reschke, J. (2011). "RFC 6266". doi:10.17487/RFC6266. Retrieved March 13, 2015. {{cite journal}}: Cite journal requires |journal= (help)

cite-note-5342. "Content-Language". HTTP Semantics. June 2022. sec. 8.5. doi:10.17487/RFC9110. RFC 9110.

cite-note-google-canonical-5443. Indicate the canonical version of a URL by responding with the Link rel="canonical" HTTP header Retrieved: 2012-02-09

cite-note-5544. W3C P3P Work Suspended

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cite-note-5746. "Retry-After". HTTP Semantics. June 2022. sec. 10.2.3. doi:10.17487/RFC9110. RFC 9110.

cite-note-5847. citerefrossgondrom2013Ross, D.; Gondrom, T. (2013). "HTTP Header Field X-Frame-Options". IETF. doi:10.17487/RFC7034. Retrieved June 12, 2014. {{cite journal}}: Cite journal requires |journal= (help)

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cite-note-6655. "CSP: report-to". Mozilla Developer Network. 2021. Retrieved May 18, 2021.

cite-note-6756. RFC 9110: HTTP Semantics

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cite-note-7059. "Clean up duration tracking and use mirroring for cross-thread access". Bugzilla@Mozilla. Retrieved February 9, 2024.

cite-note-7160. citereferic-lawrence2008Eric Lawrence (September 3, 2008). "IE8 Security Part VI: Beta 2 Update". Retrieved September 28, 2010.

cite-note-7261. "Hosting - Google Chrome Extensions - Google Code". Retrieved June 14, 2012.

cite-note-whatwg-fetch-xcto-7362. citerefvan-kesteren2016van Kesteren, Anne (August 26, 2016). "Fetch standard". WHATWG. Archived from the original on August 26, 2016. Retrieved August 26, 2016.

cite-note-7563. "X-Redirect-By HTTP response header". Retrieved May 29, 2021.

cite-note-7664. "Defining Document Compatibility: Specifying Document Compatibility Modes". April 1, 2011. Retrieved January 24, 2012.

cite-note-7765. "HTML Living Standard 4.2.5.3 Pragma directives, X-UA-Compatible state". WHATWG. March 12, 2021. Retrieved March 14, 2021. For meta elements with an http-equiv attribute in the X-UA-Compatible state, the content attribute must have a value that is an ASCII case-insensitive match for the string"IE=edge".

cite-note-7866. citereferic-lawrence2008Eric Lawrence (July 2, 2008). "IE8 Security Part IV: The XSS Filter". Retrieved September 30, 2010.

cite-note-7977. ↑ "Pragme". HTTP Caching. June 2022. sec. 5.4. doi:10.17487/RFC9111. RFC 9111.

cite-note-q234067-8078. ↑ "How to prevent caching in Internet Explorer". Microsoft. September 22, 2011. Retrieved April 15, 2015.

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.

cite-note-stackoverflow2-4267. stackoverflow2"What is the X-REQUEST-ID http header?". Retrieved March 20, 2022.

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.

cite-note-stackoverflow1-7468. stackoverflow1"Why does ASP.NET framework add the 'X-Powered-By:ASP.NET' HTTP Header in responses? - Stack Overflow". Retrieved March 20, 2022.

• Headers: Permanent Message Header Field Names

• RFC 6265: IETF HTTP State Management Mechanism

• RFC 9110: HTTP Semantics

• RFC 9111: HTTP Caching

• RFC 9112: HTTP/1.1

• RFC 9113: HTTP/2

• RFC 9114: HTTP/3

• RFC 7239: Forwarded HTTP Extension

• RFC 7240: Prefer Header for HTTP

• HTTP/1.1 headers from a web server point of view

• Internet Explorer and Custom HTTP Headers - EricLaw's IEInternals - Site Home - MSDN Blogs