Accept header
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The HTTP
Accept request and response header indicates which content types, expressed as MIME types, the sender is able to understand.
In requests, the server uses content negotiation to select one of the proposals and informs the client of the choice with the Content-Type response header.
In responses, it provides information about which content types the server can understand in messages to the requested resource, so that the content type can be used in subsequent requests to the resource.Browsers set required values for this header based on the context of the request.
For example, a browser uses different values in a request when fetching a CSS stylesheet, image, video, or a script.
| Header type | Request header, Response header |
|---|---|
| Forbidden request header | No |
| CORS-safelisted request header | Yes* |
* Values can't contain CORS-unsafe request header bytes, including
"():<>?@[\]{},, Delete 0x7F, and control characters 0x00 to 0x19, except for Tab 0x09.Syntax
http
Accept: <media-type>/<MIME_subtype>
Accept: <media-type>/*
Accept: */*
// Multiple types, weighted with the quality value syntax
Accept: text/html, application/xhtml+xml, application/xml;q=0.9, image/webp, */*;q=0.8
Directives
<media-type>/<subtype>-
A single, precise media type, like
text/html. <media-type>/*-
A media type without a subtype. For example,
image/*corresponds toimage/png,image/svg,image/gif, and other image types. */*-
Any media type.
;q=(q-factor weighting)-
A value in order of preference expressed using a relative quality value called the weight.
Examples
Using default Accept request headers
HTTP requests made using command line tools such as curl and wget use
*/* as the default Accept value:http
GET / HTTP/1.1
Host: example.com
User-Agent: curl/8.7.1
Accept: */*
Browser navigation typically has the following
Accept request header value:http
GET /en-US/ HTTP/2
Host: developer.mozilla.org
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
…
After receiving the document, the default
Accept values in requests for images on the developer.mozilla.org example look like this:http
Accept: image/avif,image/webp,image/png,image/svg+xml,image/*;q=0.8,*/*;q=0.5
Configuring Accept request headers for JSON responses
Systems that involve API interaction commonly request
application/json responses.
Here's an example of a GET request where the client specifically requests a JSON response:http
GET /users/123 HTTP/1.1
Host: example.com
Authorization: Bearer abcd123
Accept: application/json
Specifications
| Specification |
|---|
| HTTP Semantics # field.accept |
Browser compatibility
|
Chrome
|
Edge
|
Firefox
|
Opera
|
Safari
|
Chrome Android
|
Firefox for Android
|
Opera Android
|
Safari on iOS
|
Samsung Internet
|
WebView Android
|
WebView on iOS
|
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Legend
Tip: you can click/tap on a cell for more information.
Full support
See implementation notes.
See also
- HTTP content negotiation
- List of default Accept values
- CORS safelist request header restrictions
- A header with the result of the content negotiation:
Content-Type - Other similar headers:
TE,Accept-Encoding,Accept-Language
