Access-Control-Expose-Headers header

The HTTP Access-Control-Expose-Headers {{Glossary("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 {{Glossary("CORS-safelisted response header", "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.

Syntax

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

Directives

• <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 {{Glossary("CORS-safelisted response header", "CORS-safelisted response headers")}}.
• * (wildcard)
  • : Any header. 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 *.

Examples

The {{Glossary("CORS-safelisted response header", "CORS-safelisted response headers")}} are: {{HTTPHeader("Cache-Control")}}, {{HTTPHeader("Content-Language")}}, {{HTTPHeader("Content-Length")}}, {{HTTPHeader("Content-Type")}}, {{HTTPHeader("Expires")}}, {{HTTPHeader("Last-Modified")}}, {{HTTPHeader("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 Kuma-Revision, you can specify multiple headers separated by a comma:

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

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

Access-Control-Expose-Headers: *

A server can also respond with the * value for requests with credentials, but in this case it would refer to a header named *.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{HTTPHeader("Access-Control-Allow-Headers")}}
• {{HTTPHeader("Access-Control-Allow-Origin")}}