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The Access-Control-Allow-Headers response header is used in response to a preflight request which includes the Access-Control-Request-Headers to indicate which HTTP headers can be used during the actual request.

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

Header type Response header
Forbidden header name no

Syntax

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

Directives

<header-name>
The name of a supported request header. The header may list any number of headers, separated by commas.
* (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. Note that the Authorization header can't be wildcarded and always needs to be listed explicitly.

The CORS-safelisted request headers, Accept, Accept-Language, Content-Language, Content-Type are always allowed and don't need to be listed by this header necessarily. However, note that additional restrictions apply with these headers which you circumvent by listing these headers in an Access-Control-Allow-Headers header as well.

Examples

A custom header

Here's an example of what an Access-Control-Allow-Headers header might look like. It indicates that in addition to the CORS-safelisted request headers, a custom header named X-Custom-Header is supported by CORS requests to the server.

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

Multiple headers

This example shows Access-Control-Allow-Headers when it specifies support for multiple headers.

Access-Control-Allow-Headers: X-Custom-Header, Upgrade-Insecure-Requests

Bypassing additional restrictions

Although CORS-safelisted request headers are always allowed and don't usually need to be listed in Access-Control-Allow-Headers, listing them anyway will circumvent the additional restrictions that apply.

Access-Control-Allow-Headers: Accept

Example preflight request

Let's look at an example of a preflight request involving Access-Control-Allow-Headers.

Request

First, the request.  The preflight request is an OPTIONS request which includes some combination of the three preflight request headers: Access-Control-Request-Method, Access-Control-Request-Headers, and Origin, such as:

OPTIONS /resource/foo
Access-Control-Request-Method: DELETE
Access-Control-Request-Headers: origin, x-requested-with
Origin: https://foo.bar.org

Response

If the server allows CORS requests to use the DELETE method, it responds with an Access-Control-Allow-Methods response header, which lists DELETE along with the other methods it supports:

HTTP/1.1 200 OK
Content-Length: 0
Connection: keep-alive
Access-Control-Allow-Origin: https://foo.bar.org
Access-Control-Allow-Methods: POST, GET, OPTIONS, DELETE
Access-Control-Max-Age: 86400

If the requested method isn't supported, the server will respond with an error.

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Access-Control-Allow-HeadersChrome Full support 4Edge Full support 12Firefox Full support 3.5IE Full support 10Opera Full support 12Safari Full support 4WebView Android Full support 2Chrome Android Full support YesFirefox Android Full support 4Opera Android Full support 12Safari iOS Full support 3.2Samsung Internet Android Full support Yes
Wildcard (*)Chrome Full support 63Edge No support NoFirefox Full support 69IE No support NoOpera Full support 50Safari No support NoWebView Android Full support 63Chrome Android Full support 63Firefox Android No support NoOpera Android Full support 46Safari iOS No support NoSamsung Internet Android Full support 8.2

Legend

Full support  
Full support
No support  
No support

See also

Etiquetas do documento e colaboradores

Colaboradores desta página: mfuji09, AliMirlou, fscholz, wbamberg, mdnwebdocs-bot, Sheppy, othree, smaximov, teoli
Última atualização por: mfuji09,