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.

Header type Response header
Forbidden header name no


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 Servo
Basic Support4123.510124?
Feature Android Chrome for Android Edge Mobile Firefox for Android IE Mobile Opera Mobile Safari Mobile
Basic Support2.1(Yes)(Yes)1.0(Yes)123.2

Compatibility notes

See also

Document Tags and Contributors

 Contributors to this page: fscholz, teoli
 Last updated by: fscholz,