The Access-Control-Allow-Headers response header is used in response to a preflight request to indicate which HTTP headers will be available via Access-Control-Expose-Headers when making the actual request.

The simple headers, Accept, Accept-Language, Content-Language, Content-Type (but only with a MIME type of its parsed value (ignoring parameters) of either application/x-www-form-urlencoded, multipart/form-data, or text/plain), are always available and don't need to be listed by this header.

This header is required if the request has an Access-Control-Request-Headers header.


Access-Control-Allow-Headers: <header-name>, <header-name>, ...


Comma-delimited list of the supported request headers.


Access-Control-Allow-Headers: X-Custom-Header


Specification Status Comment
The definition of 'Access-Control-Allow-Headers' in that specification.
Living Standard Initial definition.

Browser compatibility

Feature Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 4 12 3.5 10 12 4
Feature Android webview Chrome for Android Edge mobile Firefox for Android IE mobile Opera Android iOS Safari
Basic support 2.1 Yes Yes 4 Yes 12 3.2

Compatibility notes

  • The wildcard value (*) that is mentioned in the latest specification, is not yet implemented in browsers:

See also

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