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Access-Control-Expose-Headers header

files/en-us/web/http/reference/headers/access-control-expose-headers/index.md

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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.

<table class="properties"> <tbody> <tr> <th scope="row">Header type</th> <td>{{Glossary("Response header")}}</td> </tr> <tr> <th scope="row">{{Glossary("Forbidden request header")}}</th> <td>No</td> </tr> </tbody> </table>

Syntax

http
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:

http
Access-Control-Expose-Headers: Content-Encoding

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

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

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

http
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")}}