Feature-Policy: sync-xhr

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This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The HTTP Feature-Policy header sync-xhr directive controls whether the current document is allowed to make synchronous XMLHttpRequest requests.

Syntax

Feature-Policy: sync-xhr <allowlist>;
<allowlist>

An allowlist is a list of origins that takes one or more of the following values:

  • *: The feature will be allowed in this document, and all nested browsing contexts (iframes) regardless of their origin.
  • 'self': The feature will be allowed in this document, and in all nested browsing contexts (iframes) in the same origin.
  • 'src': (In an iframe allow attribute only) The feature will be allowed in this iframe, as long as the document loaded into it comes from the same origin as the URL in the iframe's src attribute.
  • 'none': The feature is disabled in top-level and nested browsing contexts.
  • <origin(s)>: The feature is allowed for specific origins (for example, https://example.com). Origins should be separated by a space.

The values * (enable for all origins) or 'none' (disable for all origins) may only be used alone, while 'self' and 'src' may be used with one or more origins.

Features are each defined to have a default allowlist, which is one of:

  • *: The feature is allowed by default in top-level browsing contexts and all nested browsing contexts (iframes).
  • 'self': The feature is allowed by default in top-level browsing contexts and in nested browsing contexts (iframes) in the same origin. The feature is not allowed in cross-origin documents in nested browsing contexts.
  • 'none': The feature is disabled in top-level and nested browsing contexts.

Default policy

By default the policy is set to *, which means synchronous requests are allowed in all frames.

Specification

Specification Status Comment
Feature Policy Editor's Draft Initial definition.
WHATWG Spec Default policy is *.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
sync-xhr
Experimental
Chrome Full support 65Edge No support NoFirefox No support NoIE No support NoOpera Full support 52Safari No support NoWebView Android Full support 65Chrome Android Full support 65Firefox Android No support NoOpera Android Full support 47Safari iOS No support NoSamsung Internet Android No support No

Legend

Full support  
Full support
No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

See also

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Contribuidores para esta página: bershanskiy
Última atualização por: bershanskiy,