Access-Control-Expose-Headers

The Access-Control-Expose-Headers response header allows a server to indicate which response headers should be made available to scripts running in the browser, in response to a cross-origin request.

Only the CORS-safelisted response headers are exposed by default. For clients to be able to access other headers, the server must list them using the Access-Control-Expose-Headers header.

Access-Control-Expose-Headers: [<header-name>[, <header-name>]*]
Access-Control-Expose-Headers: *

<header-name>

A list of zero or more comma-separated header names that clients are allowed to access from a response. These are in addition to the CORS-safelisted response headers.

* (wildcard)

The value "*" only counts as a special wildcard value for requests without credentials (requests without HTTP cookies or HTTP authentication information). In requests with credentials, it is treated as the literal header name "*" without special semantics.

The CORS-safelisted response headers are: Cache-Control, Content-Language, Content-Length, Content-Type, Expires, Last-Modified, Pragma. To expose a non-CORS-safelisted response header, you can specify:

Access-Control-Expose-Headers: Content-Encoding

To additionally expose a custom header, like X-Kuma-Revision, you can specify multiple headers separated by a comma:

Access-Control-Expose-Headers: Content-Encoding, X-Kuma-Revision

For requests without credentials, a server can also respond with a wildcard value:

Access-Control-Expose-Headers: *

However, this won't wildcard the Authorization header, so if you need to expose that, you will need to list it explicitly:

Access-Control-Expose-Headers: *, Authorization

• Access-Control-Allow-Headers
• Access-Control-Allow-Origin