The HTTPSec-Fetch-Sitefetch metadata request header indicates the relationship between a request initiator's origin and the origin of the requested resource.

In other words, this header tells a server whether a request for a resource is coming from the same origin, the same site, a different site, or is a "user initiated" request. The server can then use this information to decide if the request should be allowed.

Same-origin requests would usually be allowed by default, but what happens for requests from other origins may further depend on what resource is being requested, or information in anotherfetch metadata request header. By default, requests that are not accepted should be rejected with a403 response code.

Syntax

Sec-Fetch-Site: cross-siteSec-Fetch-Site: same-originSec-Fetch-Site: same-siteSec-Fetch-Site: none

Directives

cross-site

The request initiator and the server hosting the resource have a different site (i.e., a request by "potentially-evil.com" for a resource at "example.com").

same-origin

The request initiator and the server hosting the resource have the sameorigin (same scheme, host and port).

same-site

The request initiator and the server hosting the resource have the samesite, including the scheme.

none

This request is a user-originated operation. For example: entering a URL into the address bar, opening a bookmark, or dragging-and-dropping a file into the browser window.

Examples

A fetch request tohttps://mysite.example/foo.json originating from a web page onhttps://mysite.example (with the same port) is a same-origin request.The browser will generate theSec-Fetch-Site: same-origin header as shown below, and the server will typically allow the request:

GET /foo.jsonSec-Fetch-Dest: emptySec-Fetch-Mode: corsSec-Fetch-Site: same-origin

A fetch request to the same URL from another site, for examplepotentially-evil.com, causes the browser to generate a different header (e.g.,Sec-Fetch-Site: cross-site), which the server can choose to accept or reject:

GET /foo.jsonSec-Fetch-Dest: emptySec-Fetch-Mode: corsSec-Fetch-Site: cross-site

Specifications

Browser compatibility

See also

• Sec-Fetch-Mode,Sec-Fetch-User,Sec-Fetch-Dest fetch metadata request headers
• Protect your resources from web attacks with Fetch Metadata (web.dev)
• Fetch Metadata Request Headers playground (secmetadata.appspot.com)