Fetch metadata request header

A fetch metadata request header is an HTTP request header that provides additional information about the context from which the request originated. This allows the server to make decisions about whether a request should be allowed based on where the request came from and how the resource will be used.

With this information a server can implement a resource isolation policy, allowing external sites to request only those resources that are intended for sharing, and that are used appropriately. This approach can help mitigate common cross-site web vulnerabilities such as CSRF, Cross-site Script Inclusion('XSSI'), timing attacks, and cross-origin information leaks.

These headers are prefixed with Sec-, and hence have forbidden header names. As such, they cannot be modified from JavaScript.

The fetch metadata request headers are:

• Sec-Fetch-Site
• Sec-Fetch-Mode
• Sec-Fetch-User
• Sec-Fetch-Dest

• Protect your resources from web attacks with Fetch Metadata (web.dev)
• Fetch Metadata Request Headers playground (secmetadata.appspot.com)
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• List of all HTTP headers > Fetch metadata request headers
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