Index

Found 170 pages:

# Page Tags and summary
1 HTTP headers HTTP, HTTP Header, Headers, Networking, Overview, Reference
HTTP headers let the client and the server pass additional information with an HTTP request or response. An HTTP header consists of its case-insensitive name followed by a colon (:), then by its value.
2 Accept-CH-Lifetime Client hints, HTTP, header
The Accept-CH-Lifetime header is set by the server to specify the persistence of Accept-CH header value that specifies for which Client Hints headers client should include in subsequent requests.
3 Accept-CH Client hints, HTTP, HTTP Header
The Accept-CH header is set by the server to specify which Client Hints headers a client should include in subsequent requests.
4 Accept-Charset Content Negotiation, HTTP, HTTP Header, Reference, Request header
The Accept-Charset request HTTP header was a header that advertised a client's supported character encoding. It is no longer widely used.
5 Accept-Encoding Content Negotiation, HTTP, HTTP Header, Reference, Request header
The Accept-Encoding request HTTP header advertises which content encoding, usually a compression algorithm, the client is able to understand. Using content negotiation, the server selects one of the proposals, uses it and informs the client of its choice with the Content-Encoding response header.
6 Accept-Language Accept-Language, Content Negotiation, HTTP, HTTP Header, Reference, Request header
The Accept-Language request HTTP header advertises which languages the client is able to understand, and which locale variant is preferred. (By languages, we mean natural languages, such as English, and not programming languages.) Using content negotiation, the server then selects one of the proposals, uses it and informs the client of its choice with the Content-Language response header. Browsers set adequate values for this header according to their user interface language and even if a user can change it, this happens rarely (and is frowned upon as it leads to fingerprinting).
7 Accept-Patch HTTP, Reference
The Accept-Patch response HTTP header advertises which media-type the server is able to understand in a PATCH request.
8 Accept-Post Accept-Post, HTTP, HTTP Header, Response Header
The Accept-Post response HTTP header advertises which media types are accepted by the server for HTTP post requests.
9 Accept-Ranges HTTP, HTTP Header, Range Requests, Reference, Response Header
The Accept-Ranges response HTTP header is a marker used by the server to advertise its support of partial requests. The value of this field indicates the unit that can be used to define a range.
10 Accept HTTP, HTTP Header, Reference, Request header
The Accept request HTTP header advertises which content types, expressed as MIME types, the client is able to understand. Using content negotiation, the server then selects one of the proposals, uses it and informs the client of its choice with the Content-Type response header. Browsers set adequate values for this header depending on the context where the request is done: when fetching a CSS stylesheet a different value is set for the request than when fetching an image, video or a script.
11 Access-Control-Allow-Credentials Access-Control-Allow-Credentials, CORS, HTTP, Reference, credentials, header
The Access-Control-Allow-Credentials response header tells browsers whether to expose the response to frontend JavaScript code when the request's credentials mode (Request.credentials) is include.
12 Access-Control-Allow-Headers CORS, HTTP, Reference, Response Header, header
The Access-Control-Allow-Headers response header is used in response to a preflight request which includes the Access-Control-Request-Headers to indicate which HTTP headers can be used during the actual request.
13 Access-Control-Allow-Methods CORS, HTTP, Reference, header
The Access-Control-Allow-Methods response header specifies the method or methods allowed when accessing the resource in response to a preflight request.
14 Access-Control-Allow-Origin Access Control, Access-Control-Allow-Origin, CORS, Dealing with CORS, HTTP, HTTP Header, How to Fix CORS, Reference, Security, cross-origin issue, header, origin
The Access-Control-Allow-Origin response header indicates whether the response can be shared with requesting code from the given origin.
15 Access-Control-Expose-Headers CORS, HTTP, Reference, header
The Access-Control-Expose-Headers response header allows a server to indicate which response headers should be made available to scripts running in the browser, in response to a cross-origin request.
16 Access-Control-Max-Age CORS, HTTP, Reference, header
The Access-Control-Max-Age response header indicates how long the results of a preflight request (that is the information contained in the Access-Control-Allow-Methods and Access-Control-Allow-Headers headers) can be cached.
17 Access-Control-Request-Headers CORS, HTTP, Reference, header
The Access-Control-Request-Headers request header is used by browsers when issuing a preflight request, to let the server know which HTTP headers the client might send when the actual request is made (such as with XMLHttpRequest.setRequestHeader()). This browser side header will be answered by the complementary server side header of Access-Control-Allow-Headers.
18 Access-Control-Request-Method CORS, HTTP, Reference, header
The Access-Control-Request-Method request header is used by browsers when issuing a preflight request, to let the server know which HTTP method will be used when the actual request is made. This header is necessary as the preflight request is always an OPTIONS and doesn't use the same method as the actual request.
19 Age Caching, HTTP, Response, header
The Age header contains the time in seconds the object has been in a proxy cache.
20 Allow Entity header, HTTP, HTTP Header, Reference, header
The Allow header lists the set of methods supported by a resource.
21 Alt-Svc HTTP, HTTP Header, NeedsCompatTable, Reference
The Alt-Svc HTTP header allows a server to indicate that a particular resource should be loaded from a different server — while still appearing to the user as if were loaded from the same server.
22 Authorization HTTP, HTTP Header, Reference, Request header, header
The HTTP Authorization request header contains the credentials to authenticate a user agent with a server, usually, but not necessarily, after the server has responded with a 401 Unauthorized status and the WWW-Authenticate header.
23 Cache-Control Cache-Control, General Header, HTTP, HTTP Header, Reference
The Cache-Control HTTP header holds directives (instructions) for caching in both requests and responses. A given directive in a request does not mean the same directive should be in the response.
24 Clear-Site-Data HTTP, HTTP Header, Reference, Response Header, header
The Clear-Site-Data header clears browsing data (cookies, storage, cache) associated with the requesting website. It allows web developers to have more control over the data stored locally by a browser for their origins.
25 Connection HTTP, Headers, Reference, Web
The Connection general header controls whether or not the network connection stays open after the current transaction finishes. If the value sent is keep-alive, the connection is persistent and not closed, allowing for subsequent requests to the same server to be done.
26 Content-Disposition HTTP, Reference, header
In a regular HTTP response, the Content-Disposition response header is a header indicating if the content is expected to be displayed inline in the browser, that is, as a Web page or as part of a Web page, or as an attachment, that is downloaded and saved locally.
27 Content-Encoding HTTP, Headers, Reference
The Content-Encoding representation header lists any encodings that have been applied to the representation (message payload), and in what order. This lets the recipient know how to decode the representation in order to obtain the original payload format. Content encoding is mainly used to compress the message data without losing information about the origin media type.
28 Content-Language HTTP, Headers, Reference
The Content-Language representation header is used to describe the language(s) intended for the audience, so that it allows a user to differentiate according to the users' own preferred language.
29 Content-Length HTTP, Headers, Reference
The Content-Length entity header indicates the size of the entity-body, in bytes, sent to the recipient.
30 Content-Location HTTP, Reference, header
The Content-Location header indicates an alternate location for the returned data. The principal use is to indicate the URL of a resource transmitted as the result of content negotiation.
31 Content-Range HTTP, HTTP Header, Reference, Response Header, header
The Content-Range response HTTP header indicates where in a full body message a partial message belongs.
32 Content-Security-Policy-Report-Only CSP, HTTP, HTTPS, Reference, Security, header
The HTTP Content-Security-Policy-Report-Only response header allows web developers to experiment with policies by monitoring (but not enforcing) their effects. These violation reports consist of JSON documents sent via an HTTP POST request to the specified URI.
33 Content-Security-Policy CSP, Content Security Policy, HTTP, Reference, Security, header
The HTTP Content-Security-Policy response header allows web site administrators to control resources the user agent is allowed to load for a given page. With a few exceptions, policies mostly involve specifying server origins and script endpoints. This helps guard against cross-site scripting attacks (XSS).
34 CSP: base-uri CSP, Directive, Document directive, HTTP, Security
The HTTP Content-Security-Policy base-uri directive restricts the URLs which can be used in a document's base element. If this value is absent, then any URI is allowed. If this directive is absent, the user agent will use the value in the base element.
35 CSP: block-all-mixed-content CSP, Content-Security-Policy, Directive, HTTP, Mixed Content, Reference, Security, block-all-mixed-content
The HTTP Content-Security-Policy (CSP) block-all-mixed-content directive prevents loading any assets over HTTP when the page uses HTTPS.
36 CSP: child-src CSP, Child, Content-Security-Policy, Directive, HTTP, Reference, Security, child-src, source
The HTTP Content-Security-Policy (CSP) child-src directive defines the valid sources for web workers and nested browsing contexts loaded using elements such as frame and iframe. For workers, non-compliant requests are treated as fatal network errors by the user agent.
37 CSP: connect-src CSP, Content-Security-Policy, Directive, HTTP, Reference, Security, connect-src, source
The HTTP Content-Security-Policy (CSP) connect-src directive restricts the URLs which can be loaded using script interfaces. The APIs that are restricted are:
38 CSP: default-src CSP, Content-Security-Policy, Directive, HTTP, Reference, Security, default, default-src, source
The HTTP Content-Security-Policy (CSP) default-src directive serves as a fallback for the other CSP fetch directive.
39 CSP: font-src CSP, Content-Security-Policy, Directive, HTTP, Reference, Security, font, source
The HTTP Content-Security-Policy (CSP) font-src directive specifies valid sources for fonts loaded using @font-face.
40 CSP: form-action CSP, Content-Security-Policy, Directive, HTTP, Security, action, form, form-action
The HTTP Content-Security-Policy (CSP) form-action directive restricts the URLs which can be used as the target of a form submissions from a given context.
41 CSP: frame-ancestors Ancestors, CSP, Content-Security-Policy, Directive, Frame, HTTP, Security, frame-ancestors
The HTTP Content-Security-Policy (CSP) frame-ancestors directive specifies valid parents that may embed a page using frame, iframe, object, embed, or applet.
42 CSP: frame-src CSP, Content-Security-Policy, Directive, Frame, HTTP, Reference, Security, frame-src, source
The HTTP Content-Security-Policy (CSP) frame-src directive specifies valid sources for nested browsing contexts loading using elements such as frame and iframe.
43 CSP: img-src CSP, Content-Security-Policy, Directive, HTTP, Image, Reference, Security, img-src, source
The HTTP Content-Security-Policy img-src directive specifies valid sources of images and favicons.
44 CSP: manifest-src CSP, Content-Security-Policy, Directive, HTTP, Manifest, Reference, Security, manifest-src, source
The HTTP Content-Security-Policy: manifest-src directive specifies which manifest can be applied to the resource.
45 CSP: media-src CSP, Content-Security-Policy, Directive, HTTP, Media, Reference, Security, media-src, source
The HTTP Content-Security-Policy (CSP) media-src directive specifies valid sources for loading media using the audio and video elements.
46 CSP: navigate-to CSP, Content-Security-Policy, Directive, HTTP, Navigation, Reference, Security
The HTTP Content-Security-Policy (CSP) navigate-to directive restricts the URLs to which a document can initiate navigations by any means including form (if form-action is not specified), a, window.location, window.open, etc. This is an enforcement on what navigations this document initiates not on what this document is allowed to navigate to.
47 CSP: object-src CSP, Content-Security-Policy, Directive, HTTP, Object, Reference, Security, object-src, source
The HTTP Content-Security-Policy object-src directive specifies valid sources for the object, embed, and applet elements.
48 CSP: plugin-types CSP, Content-Security-Policy, Directive, Flash, HTTP, Java, Plugin, Plugins, Security
The HTTP Content-Security-Policy (CSP) plugin-types directive restricts the set of plugins that can be embedded into a document by limiting the types of resources which can be loaded.
49 CSP: prefetch-src CSP, Content Security Policy, Directive, HTTP, Reference, prefetch-src
The HTTP Content-Security-Policy (CSP) prefetch-src directive specifies valid resources that may be prefetched or prerendered.
50 CSP: referrer CSP, Content-Security-Policy, Directive, HTTP, Obsolete, Reference, Security, referrer
The HTTP Content-Security-Policy (CSP) referrer directive used to specify information in the Referer header (with a single r as this was a typo in the original spec) for links away from a page. This API is deprecated and removed from browsers.
51 CSP: report-to CSP, Content Security Policy, Content-Security-Policy, HTTP, Reporting, Security, report-to
The Content-Security-Policy Report-To HTTP response header field instructs the user agent to store reporting endpoints for an origin.
52 CSP: report-uri CSP, Directive, HTTP, Reference, Security
The deprecated HTTP Content-Security-Policy (CSP) report-uri directive instructs the user agent to report attempts to violate the Content Security Policy. These violation reports consist of JSON documents sent via an HTTP POST request to the specified URI.
53 CSP: require-sri-for CSP, Directive, HTTP, Reference, Security, Subresource Integrity, require-sri-for
The HTTP Content-Security-Policy require-sri-for directive instructs the client to require the use of Subresource Integrity for scripts or styles on the page.
54 CSP: require-trusted-types-for CSP, Directive, HTTP, Security
The HTTP Content-Security-Policy (CSP) require-trusted-types-for  directive instructs user agents to control the data passed to DOM XSS sink functions, like Element.innerHTML setter.
55 CSP: sandbox CSP, Content-Security-Policy, Directive, HTTP, Sandbox, Security
The HTTP Content-Security-Policy (CSP) sandbox directive enables a sandbox for the requested resource similar to the iframe sandbox attribute. It applies restrictions to a page's actions including preventing popups, preventing the execution of plugins and scripts, and enforcing a same-origin policy.
56 CSP: script-src-attr CSP, Content, Content-Security-Policy, Directive, HTTP, Reference, Script, Security, script-src, source
The HTTP Content-Security-Policy (CSP) script-src-attr directive specifies valid sources for JavaScript inline event handlers. This includes only inline script event handlers like onclick, but not URLs loaded directly into script elements.
57 CSP: script-src-elem CSP, Content, Content-Security-Policy, Directive, HTTP, Reference, Script, Security, script-src, source
The HTTP Content-Security-Policy (CSP) script-src-elem directive specifies valid sources for JavaScript script elements, but not inline script event handlers like onclick.
58 CSP: script-src CSP, Content, Content-Security-Policy, Directive, HTTP, Reference, Script, Security, script-src, source
The HTTP Content-Security-Policy (CSP) script-src directive specifies valid sources for JavaScript. This includes not only URLs loaded directly into script elements, but also things like inline script event handlers (onclick) and XSLT stylesheets which can trigger script execution.
59 CSP: style-src-attr CSP, Content, Content-Security-Policy, Directive, HTTP, Reference, Security, Style, source, style-src, style-src-attr
The HTTP Content-Security-Policy (CSP) style-src-attr directive specifies valid sources for inline styles applied to individual DOM elements.
60 CSP: style-src-elem CSP, Content, Content-Security-Policy, Directive, HTTP, Reference, Security, Style, source, style-src, style-src-elem
The HTTP Content-Security-Policy (CSP) style-src-elem directive specifies valid sources for stylesheets style elements and link elements with rel="stylesheet".
61 CSP: style-src CSP, Content, Content-Security-Policy, Directive, HTTP, Reference, Security, Style, source, style-src
The HTTP Content-Security-Policy (CSP) style-src directive specifies valid sources for stylesheets.
62 CSP: trusted-types CSP, Directive, HTTP, Security
The HTTP Content-Security-Policy (CSP) trusted-types directive instructs user agents to restrict the creation of Trusted Types policies - functions that build non-spoofable, typed values intended to be passed to DOM XSS sinks in place of strings.
63 CSP: upgrade-insecure-requests CSP, Content-Security-Policy, Directive, HTTP, Reference, Requests, Security, Upgrade, upgrade-insecure-requests
The HTTP Content-Security-Policy (CSP) upgrade-insecure-requests directive instructs user agents to treat all of a site's insecure URLs (those served over HTTP) as though they have been replaced with secure URLs (those served over HTTPS). This directive is intended for web sites with large numbers of insecure legacy URLs that need to be rewritten.
64 CSP: worker-src CSP, Content-Security-Policy, Directive, HTTP, Reference, Security
The HTTP Content-Security-Policy (CSP) worker-src directive specifies valid sources for Worker, SharedWorker, or ServiceWorker scripts.
65 Content-Type Content-Type, Entity header, HTTP, Reference, header
The Content-Type entity header is used to indicate the MIME type of the resource.
66 Cookie Cookies, HTTP, Reference, header, request
The Cookie HTTP request header contains stored HTTP cookies associated with the server (i.e. previously sent by the server with the Set-Cookie header or set in Javascript using Document.cookie).
67 Cookie2 HTTP, Obsolete, Reference, header, request
The obsolete Cookie2 HTTP request header used to advise the server that the user agent understands "new-style" cookies, but nowadays user agents will use the Cookie header instead, not this one.
68 Cross-Origin-Embedder-Policy HTTP, HTTP Header, Reference, Response Header, header
The HTTP Cross-Origin-Embedder-Policy (COEP) response header prevents a document from loading any cross-origin resources that don't explicitly grant the document permission (using CORP or CORS).
69 Cross-Origin-Opener-Policy HTTP, HTTP Header, Reference, Response Header, header
The HTTP Cross-Origin-Opener-Policy (COOP) response header allows you to ensure a top-level document does not share a browsing context group with cross-origin documents.
70 Cross-Origin-Resource-Policy HTTP, HTTP Header, Reference, Response Header, header
The HTTP Cross-Origin-Resource-Policy response header conveys a desire that the browser blocks no-cors cross-origin/cross-site requests to the given resource.
71 Date General Header, HTTP, Reference, header
The Date general HTTP header contains the date and time at which the message was originated.
72 Device-Memory Client hints, Device Memory API, HTTP, HTTP Header
The Device-Memory header is a Device Memory API header that works like Client Hints header which represents the approximate amount of RAM client device has.
73 Digest HTTP, HTTP Header
The Digest response HTTP header provides a digest of the requested resource.
74 DNT DNT, HTTP, Reference, header
The DNT (Do Not Track) request header indicates the user's tracking preference. It lets users indicate whether they would prefer privacy rather than personalized content.
75 DPR Client hints, HTTP, HTTP Header, Non-standard, Obsolete
The DPR header is a Client Hints header which represents the client device pixel ratio (DPR), which is the number of physical device pixels corresponding to every CSS pixel.
76 Early-Data Client hints, HTTP, header, request
The Early-Data header is set by an intermediary to indicate that the request has been conveyed in TLS early data, and also indicates that the intermediary understands the 425 status code.
77 ETag HTTP, Reference, Response, header
The ETag HTTP response header is an identifier for a specific version of a resource. It lets caches be more efficient and save bandwidth, as a web server does not need to resend a full response if the content has not changed. Additionally, etags help prevent simultaneous updates of a resource from overwriting each other ("mid-air collisions").
78 Expect-CT HTTP, Reference, header
The Expect-CT header lets sites opt in to reporting and/or enforcement of Certificate Transparency requirements, to prevent the use of misissued certificates for that site from going unnoticed.
79 Expect HTTP, HTTP Header, Reference, Request header
The Expect HTTP request header indicates expectations that need to be fulfilled by the server in order to properly handle the request.
80 Expires Caching, HTTP, Response, header
The Expires header contains the date/time after which the response is considered stale.
81 Feature-Policy Authorization, Experimental, Feature Policy, Feature-Policy, HTTP, Permissions, Reference, Security, Web, header
The HTTP Feature-Policy header provides a mechanism to allow and deny the use of browser features in its own frame, and in content within any iframe elements in the document.
82 Feature-Policy: accelerometer Accelerometer, Directive, Feature Policy, HTTP, Reference
The HTTP Feature-Policy header accelerometer directive controls whether the current document is allowed to gather information about the acceleration of the device through the Accelerometer interface.
83 Feature-Policy: ambient-light-sensor Ambient Light Sensor, Feature Policy, HTTP
The HTTP Feature-Policy header ambient-light-sensor directive controls whether the current document is allowed to gather information about the amount of light in the environment around the device through the AmbientLightSensor interface.
84 Feature-Policy: autoplay Directive, Feature Policy, Feature-Policy, HTTP, Reference, autoplay
The HTTP Feature-Policy header autoplay directive controls whether the current document is allowed to autoplay media requested through the HTMLMediaElement interface.
85 Feature-Policy: battery
The HTTP Feature-Policy header battery directive controls whether the current document is allowed to gather information about the battery of the device through the BatteryManager interface obtained via Navigator.getBattery.
86 Feature-Policy: camera Directive, Feature Policy, Feature-Policy, HTTP, Reference, camera
The HTTP Feature-Policy header camera directive controls whether the current document is allowed to use video input devices. When this policy is enabled, the Promise returned by MediaDevices.getUserMedia() will reject with a NotAllowedError.
87 Feature-Policy: display-capture
The HTTP Feature-Policy header display-capture directive controls whether or not the document is permitted to use Screen Capture API, i.e.,MediaDevices.getDisplayMedia to capture the screen's contents.
88 Feature-Policy: document-domain Directive, Experimental, Feature Policy, Feature-Policy, HTTP, Reference, document-domain, header
The HTTP Feature-Policy header document-domain directive controls whether the current document is allowed to set document.domain. When this policy is disabled, attempting to set document.domain will fail and cause a SecurityError DOMException to be thrown.
89 Feature-Policy: encrypted-media Directive, EME, Feature Policy, Feature-Policy, HTTP, Reference
The HTTP Feature-Policy header encrypted-media directive controls whether the current document is allowed to use the Encrypted Media Extensions API (EME). When this policy is enabled, the Promise returned by Navigator.requestMediaKeySystemAccess will reject with a DOMException.
90 Feature-Policy: fullscreen Feature Policy, Feature-Policy, HTTP, fullscreen, header
The HTTP Feature-Policy header fullscreen directive controls whether the current document is allowed to use Element.requestFullScreen(). When this policy is enabled, the returned Promise rejects with a TypeError.
91 Feature-Policy: geolocation Feature Policy, Feature-Policy, Geolocation, HTTP, header
The HTTP Feature-Policy header geolocation directive controls whether the current document is allowed to use the Geolocation Interface. When this policy is enabled, calls to Geolocation.getCurrentPosition and Geolocation.watchPosition will cause those functions' callbacks to be invoked with a GeolocationPositionError code of PERMISSION_DENIED.
92 Feature-Policy: gyroscope
The HTTP Feature-Policy header gyroscope directive controls whether the current document is allowed to gather information about the orientation of the device through the Gyroscope interface.
93 Feature-Policy: layout-animations Directive, Feature-Policy, HTTP, Reference, layout-animations
The HTTP Feature-Policy header layout-animations directive controls whether the current document is allowed to show layout animations.
94 Feature-Policy: legacy-image-formats Direcive, Feature-Policy, HTTP, Reference, legacy-image-formats
The HTTP Feature-Policy header legacy-image-formats directive controls whether the current document is allowed to display images in legacy formats.
95 Feature-Policy: magnetometer Directive, Feature-Policy, HTTP, Magnetometer, Reference
The HTTP Feature-Policy header magnetometer directive controls whether the current document is allowed to gather information about the orientation of the device through the Magnetometer interface.
96 Feature-Policy: microphone Feature Policy, Feature-Policy, HTTP, header, microphone
The HTTP Feature-Policy header microphone directive controls whether the current document is allowed to use audio input devices. When this policy is enabled, the Promise returned by MediaDevices.getUserMedia() will reject with a NotAllowedError.
97 Feature-Policy: midi Directive, Feature Policy, Feature-Policy, HTTP, MIDI, Reference
The HTTP Feature-Policy header midi directive controls whether the current document is allowed to use the Web MIDI API. When this policy is enabled, the Promise returned by Navigator.requestMIDIAccess() will reject with a DOMException.
98 Feature-Policy: oversized-images Directive, Feature-Policy, HTTP, Reference
The HTTP Feature-Policy header oversized-images directive controls whether the current document is allowed to download and display large images.
99 Feature-Policy: payment Directive, Feature Policy, Feature-Policy, HTTP, Payment Request API, Payments API, Reference
The HTTP Feature-Policy header field's payment directive controls whether the current document is allowed to use the Payment Request API. When this policy is disabled, the PaymentRequest() constructor will throw a SyntaxError.
100 Feature-Policy: picture-in-picture Directive, Feature-Policy, HTTP, Picture in picture, Reference
The HTTP Feature-Policy header picture-in-picture directive controls whether the current document is allowed to play a video in a Picture-in-Picture mode via the corresponding API.
101 Feature-Policy: publickey-credentials-get
The HTTP Feature-Policy header publickey-credentials-get directive controls whether the current document is allowed to access the Web Authentication API to retrieve public-key credentials; i.e, via CredentialsContainer.get.
102 Feature-Policy: screen-wake-lock
The HTTP Feature-Policy header screen-wake-lock directive controls whether the current document is allowed to use Screen Wake Lock API to indicate that device should not dim or turn off the screen.
103 Feature-Policy: sync-xhr Directive, Feature Policy, Feature-Policy, HTTP, Reference, XMLHttpRequest
The HTTP Feature-Policy header sync-xhr directive controls whether the current document is allowed to make synchronous XMLHttpRequest requests.
104 Feature-Policy: unoptimized-images Directive, Feature-Policy, HTTP, Image, Reference
The HTTP Feature-Policy header unoptimized-images directive controls whether the current document is allowed to download and display unoptimized images.
105 Feature-Policy: unsized-media Directive, Feature-Policy, HTTP, Reference
The HTTP Feature-Policy header unsized-media directive controls whether the current document is allowed to change the size of media elements after the initial layout is complete.
106 Feature-Policy: usb Directive, Feature-Policy, HTTP, Reference, Vibration API, Web USB
The HTTP Feature-Policy header usb directive controls whether the current document is allowed to use the WebUSB API.
107 Feature-Policy: vibrate Directive, Feature-Policy, HTTP, Reference, Vibration API
The HTTP Feature-Policy header vibrate  directive controls whether the current document is allowed to trigger device vibrations via Navigator.vibrate method of Vibration API.
108 Feature-Policy: vr Directive, Feature Policy, Feature-Policy, HTTP, Reference, WebVR
The HTTP Feature-Policy header vr directive controls whether the current document is allowed to use the WebVR API. When this policy is enabled, the Promise returned by Navigator.getVRDisplays will reject with a DOMException.
109 Feature-Policy: wake-lock Directive, Feature-Policy, HTTP, Reference, Wake Lock API
Note: This API is still actively being developed and available only behind a flag on select browsers and platforms.
110 web-share Feature-Policy, HTTP, Web Share
The HTTP Feature-Policy header web-share directive controls whether the current document is allowed to use the Navigator.share method of the Web Share API to share text, links, images, and other content to arbitrary destinations of the user's choice.
111 Feature-Policy: xr-spatial-tracking
The HTTP Feature-Policy header xr-spatial-tracking directive controls whether the current document is allowed to use the WebXR Device API. This policy controls whether XRSystem/requestSession can return XRSession that requires spatial tracking and whether user agent can indicate support for sessions supporting spatial tracking via XRSystem/isSessionSupported and devicechange event on Navigator.xr object.
112 Feature-Policy: xr
This Feature Policy directive was at one point defined as xr (but implemented in Chrome as Feature-Policy/vr), use Feature-Policy/xr-spatial-tracking instead.
113 Forwarded HTTP, HTTP Header, Reference, Request header, header
The Forwarded header contains information from the reverse proxy servers that is altered or lost when a proxy is involved in the path of the request.
114 From HTTP, Reference, header
The From request header contains an Internet email address for a human user who controls the requesting user agent.
115 Host HTTP, Reference, header
The Host request header specifies the host and port number of the server to which the request is being sent.
116 If-Match Conditional Requests, HTTP, HTTP Header, Reference, Request header
The If-Match HTTP request header makes the request conditional. For GET and HEAD methods, the server will send back the requested resource only if it matches one of the listed ETags. For PUT and other non-safe methods, it will only upload the resource in this case.
117 If-Modified-Since Conditional Requests, HTTP, HTTP Header, Reference, Request header
The If-Modified-Since request HTTP header makes the request conditional: the server will send back the requested resource, with a 200 status, only if it has been last modified after the given date. If the resource has not been modified since, the response will be a 304 without any body; the Last-Modified response header of a previous request will contain the date of last modification. Unlike If-Unmodified-Since, If-Modified-Since can only be used with a GET or HEAD.
118 If-None-Match Conditional Requests, HTTP, HTTP Header, Reference, Request header
The If-None-Match HTTP request header makes the request conditional. For GET and HEAD methods, the server will send back the requested resource, with a 200 status, only if it doesn't have an ETag matching the given ones. For other methods, the request will be processed only if the eventually existing resource's ETag doesn't match any of the values listed.
119 If-Range Condtional Requests, HTTP, HTTP Header, Range Requests, Reference, Request header
The If-Range HTTP request header makes a range request conditional: if the condition is fulfilled, the range request will be issued and the server sends back a 206 Partial Content answer with the appropriate body. If the condition is not fulfilled, the full resource is sent back, with a 200 OK status.
120 If-Unmodified-Since HTTP, HTTP Header, Reference, Request header
The If-Unmodified-Since request HTTP header makes the request conditional: the server will send back the requested resource, or accept it in the case of a POST or another non-safe method, only if it has not been last modified after the given date. If the resource has been modified after the given date, the response will be a 412 (Precondition Failed) error.
121 Keep-Alive General Header, HTTP, HTTP Header, Reference
The Keep-Alive general header allows the sender to hint about how the connection may be used to set a timeout and a maximum amount of requests.
122 Large-Allocation HTTP, HTTP Header, Non-standard, Reference, Response Header, header
The non-standard Large-Allocation response header tells the browser that the page being loaded is going to want to perform a large allocation. It is currently only implemented in Firefox, but is harmless to send to every browser.
123 Last-Modified HTTP, HTTP Header, Reference, Response Header
The Last-Modified response HTTP header contains the date and time at which the origin server believes the resource was last modified. It is used as a validator to determine if a resource received or stored is the same. Less accurate than an ETag header, it is a fallback mechanism. Conditional requests containing If-Modified-Since or If-Unmodified-Since headers make use of this field.
124 Link Draft, HTTP, HTTP Header, Link, NeedsCompatTable, NeedsContent, NeedsSyntax, Reference
The HTTP Link entity-header field provides a means for serialising one or more links in HTTP headers. It is semantically equivalent to the HTML link element.
125 Location HTTP, HTTP Header, Reference, Response Header
The Location response header indicates the URL to redirect a page to. It only provides a meaning when served with a 3xx (redirection) or 201 (created) status response.
126 NEL HTTP, HTTP Header, Network Error Logging, Reference, Response Header, header
The HTTP NEL response header is used to configure network request logging.
127 Origin HTTP, Reference, Request header, header, origin
The Origin request header indicates where a request originates from. It doesn't include any path information. It is similar to the Referer header, but, unlike that header, it doesn't disclose the whole path.
128 Pragma Caching, Deprecated, HTTP, header, request
The Pragma HTTP/1.0 general header is an implementation-specific header that may have various effects along the request-response chain. It is used for backwards compatibility with HTTP/1.0 caches where the Cache-Control HTTP/1.1 header is not yet present.
129 Proxy-Authenticate HTTP, HTTP Header, Proxy, Reference, Response Header
The HTTP Proxy-Authenticate response header defines the authentication method that should be used to gain access to a resource behind a proxy server. It authenticates the request to the proxy server, allowing it to transmit the request further.
130 Proxy-Authorization HTTP, HTTP Header, Reference, Request header, header
The HTTP Proxy-Authorization request header contains the credentials to authenticate a user agent to a proxy server, usually after the server has responded with a 407 Proxy Authentication Required status and the Proxy-Authenticate header.
131 Public-Key-Pins-Report-Only Deprecated, HPKP, HTTP, Obsolete, Security, header
The HTTP Public-Key-Pins-Report-Only response header was used to send reports of pinning violation to the report-uri specified in the header but, unlike Public-Key-Pins still allows browsers to connect to the server if the pinning is violated. The header is silently ignored in modern browsers as support for HPKP has been removed. Use Certificate Transparency and the Expect-CT header instead.
132 Public-Key-Pins Deprecated, HPKP, HTTP, Obsolete, Reference, Security, header
The HTTP Public-Key-Pins response header used to associate a specific cryptographic public key with a certain web server to decrease the risk of MITM attacks with forged certificates, however, it has been removed from modern browsers and is no longer supported. Use Certificate Transparency and Expect-CT header instead.
133 Range HTTP, HTTP Header, Range Requests, Reference, Request header
The Range HTTP request header indicates the part of a document that the server should return. Several parts can be requested with one Range header at once, and the server may send back these ranges in a multipart document. If the server sends back ranges, it uses the 206 Partial Content for the response. If the ranges are invalid, the server returns the 416 Range Not Satisfiable error. The server can also ignore the Range header and return the whole document with a 200 status code.
134 Referer HTTP, Reference, header, referer, referrer
The Referer HTTP request header contains an absolute or partial address of the page making the request. When following a link, this would be the address of the page containing the link. When making resource requests to another domain, this would be the address of the page using the resource. The Referer header allows servers to identify where people are visiting them from, which can then be used for analytics, logging, optimized caching, and more.
135 Referrer-Policy HTTP, HTTP Header, Privacy, Reference, Referrer-Policy, Response, Response Header, referrer
The Referrer-Policy HTTP header controls how much referrer information (sent via the Referer header) should be included with requests. Aside from the HTTP header, you can set this policy in HTML.
136 Retry-After HTTP, Reference, Response, Response Header, header
The Retry-After response HTTP header indicates how long the user agent should wait before making a follow-up request. There are three main cases this header is used:
137 Save-Data HTTP, HTTP Header, Reference, Request header, Save-Data, header
The Save-Data header field is a boolean which, in requests, indicates the client's preference for reduced data usage. This could be for reasons such as high transfer costs, slow connection speeds, etc.
138 Sec-Fetch-Dest Fetch Metadata Request Headers, HTTP, HTTP Headers
The Sec-Fetch-Dest fetch metadata header indicates the request's destination, that is how the fetched data will be used.
139 Sec-Fetch-Mode Fetch Metadata Request Headers, HTTP, HTTP Header
The Sec-Fetch-Mode fetch metadata header indicates the request's mode.
140 Sec-Fetch-Site Fetch Metadata Request Headers, HTTP, HTTP Header
The Sec-Fetch-Site fetch metadata header indicates the relationship between a request initiator's origin and the origin of the resource.
141 Sec-Fetch-User Fetch metadate request headers, HTTP, HTTP Headers
The Sec-Fetch-User fetch metadata header is only sent for requests initiated by user activation, and its value will always be ?1.
142 Sec-WebSocket-Accept Draft, HTTP, NeedsCompatTable, NeedsContent, Reference, Sec-WebSocket-Accept, WebSockets, header
The Sec-WebSocket-Accept header is used in the websocket opening handshake. It would appear in the response headers. That is, this is header is sent from server to client to inform that server is willing to initiate a websocket connection.
143 Server-Timing HTTP, Performance, Reference, header
The Server-Timing header communicates one or more metrics and descriptions for a given request-response cycle. It is used to surface any backend server timing metrics (e.g. database read/write, CPU time, file system access, etc.) in the developer tools in the user's browser or in the PerformanceServerTiming interface.
144 Server HTTP, Reference, header
The Server header describes the software used by the origin server that handled the request — that is, the server that generated the response.
145 Set-Cookie Cookies, HTTP, Reference, Response, header, samesite
The Set-Cookie HTTP response header is used to send a cookie from the server to the user agent, so the user agent can send it back to the server later. To send multiple cookies, multiple Set-Cookie
146 SameSite cookies Cookies, HTTP, Reference, samesite
The SameSite attribute of the Set-Cookie HTTP response header allows you to declare if your cookie should be restricted to a first-party or same-site context.
147 Set-Cookie2 Cookies, HTTP, Obsolete, Reference, header
The obsolete Set-Cookie2 HTTP response header used to send cookies from the server to the user agent, but has been deprecated by the specification. Use Set-Cookie instead.
148 SourceMap HTTP, HTTP Header, Reference, Response Header, header
The SourceMap HTTP response header links generated code to a source map, enabling the browser to reconstruct the original source and present the reconstructed original in the debugger.
149 Strict-Transport-Security HSTS, HTTP, HTTPS, Security, header
The HTTP Strict-Transport-Security response header (often abbreviated as HSTS) lets a web site tell browsers that it should only be accessed using HTTPS, instead of using HTTP.
150 TE HTTP, Reference, header
The TE request header specifies the transfer encodings the user agent is willing to accept. (you could informally call it Accept-Transfer-Encoding, which would be more intuitive).
151 Timing-Allow-Origin CORS, HTTP, Reference, Timing-Allow-Origin, header
The 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.
152 Tk DNT, HTTP, Reference, Response, header, tracking
The Tk response header indicates the tracking status that applied to the corresponding request.
153 Trailer HTTP, Reference, header
The Trailer response header allows the sender to include additional fields at the end of chunked messages in order to supply metadata that might be dynamically generated while the message body is sent, such as a message integrity check, digital signature, or post-processing status.
154 Transfer-Encoding HTTP, Reference, header
The Transfer-Encoding header specifies the form of encoding used to safely transfer the Payload body to the user.
155 Upgrade-Insecure-Requests HTTP, HTTPS, Security, header
The HTTP Upgrade-Insecure-Requests request header sends a signal to the server expressing the client’s preference for an encrypted and authenticated response, and that it can successfully handle the upgrade-insecure-requests CSP directive.
156 Upgrade HTTP, HTTP Header, Upgrade
The HTTP 1.1 (only) Upgrade header can be used to upgrade an already established client/server connection to a different protocol (over the same transport protocol). For example, it can be used by a client to upgrade a connection from HTTP 1.1 to HTTP 2.0, or an HTTP or HTTPS connection into a WebSocket.
157 User-Agent HTTP, HTTP Header, Reference, User-agent
The User-Agent request header is a characteristic string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent.
158 Firefox user agent string reference Compatibility, Firefox, Firefox 4, Gecko, Gecko 2.0, Guide
This document describes the user agent string used in Firefox 4 and later and applications based on Gecko 2.0 and later. For a breakdown of changes to the string in Gecko 2.0, see Final User Agent string for Firefox 4 (blog post). See also this document on user agent sniffing and this Hacks blog post.
159 Vary HTTP, Reference, Response, Response Header, header
The Vary HTTP response header determines how to match future request headers to decide whether a cached response can be used rather than requesting a fresh one from the origin server. It is used by the server to indicate which headers it used when selecting a representation of a resource in a content negotiation algorithm.
160 Via HTTP, Reference, header
The Via general header is added by proxies, both forward and reverse proxies, and can appear in the request headers and the response headers. It is used for tracking message forwards, avoiding request loops, and identifying the protocol capabilities of senders along the request/response chain.
161 Want-Digest HTTP, HTTP Header
The Want-Digest HTTP header is primarily used in a HTTP request, to ask the responder to provide a digest of the requested resource using the Digest response header.
162 Warning General Header, HTTP, Reference, header
The Warning general HTTP header contains information about possible problems with the status of the message. More than one Warning header may appear in a response.
163 WWW-Authenticate HTTP, HTTP Header, Reference, Response Header, header
The HTTP WWW-Authenticate response header defines the authentication method that should be used to gain access to a resource.
164 X-Content-Type-Options HTTP, HTTP Header, Reference, Response Header
The X-Content-Type-Options response HTTP header is a marker used by the server to indicate that the MIME types advertised in the Content-Type headers should not be changed and be followed. This is a way to opt out of MIME type sniffing, or, in other words, to say that the MIME types are deliberately configured.
165 X-DNS-Prefetch-Control DNS, HTTP, X-DNS-Prefetch-Control, header
The X-DNS-Prefetch-Control HTTP response header controls DNS prefetching, a feature by which browsers proactively perform domain name resolution on both links that the user may choose to follow as well as URLs for items referenced by the document, including images, CSS, JavaScript, and so forth.
166 X-Forwarded-For HTTP, HTTP Header, Non-standard, Reference, Request header, header
The X-Forwarded-For (XFF) header is a de-facto standard header for identifying the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When traffic is intercepted between clients and servers, server access logs contain the IP address of the proxy or load balancer only. To see the original IP address of the client, the X-Forwarded-For request header is used.
167 X-Forwarded-Host HTTP, HTTP Header, Non-standard, Reference, Request header, header
The X-Forwarded-Host (XFH) header is a de-facto standard header for identifying the original host requested by the client in the Host HTTP request header.
168 X-Forwarded-Proto HTTP, HTTP Header, Non-standard, Reference, Request header, header
The X-Forwarded-Proto (XFP) header is a de-facto standard header for identifying the protocol (HTTP or HTTPS) that a client used to connect to your proxy or load balancer. Your server access logs contain the protocol used between the server and the load balancer, but not the protocol used between the client and the load balancer. To determine the protocol used between the client and the load balancer, the X-Forwarded-Proto request header can be used.
169 X-Frame-Options Gecko, HAProxy, HTTP, Response Header, Security, nginx
The X-Frame-Options HTTP response header can be used to indicate whether or not a browser should be allowed to render a page in a frame, iframe, embed or object. Sites can use this to avoid click-jacking attacks, by ensuring that their content is not embedded into other sites.
170 X-XSS-Protection HTTP, Reference, Security, XSS, header
The HTTP X-XSS-Protection response header is a feature of Internet Explorer, Chrome and Safari that stops pages from loading when they detect reflected cross-site scripting (XSS) attacks. Although these protections are largely unnecessary in modern browsers when sites implement a strong Content-Security-Policy that disables the use of inline JavaScript ('unsafe-inline'), they can still provide protections for users of older web browsers that don't yet support CSP.