Sec-CH-UA-Bitness

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The HTTP Sec-CH-UA-Bitness request header is a user agent client hint which provides the "bitness" of the user-agent's underlying CPU architecture. This is the size in bits of an integer or memory address—typically 64 or 32 bits.

This might be used by a server, for example, to select and offer the correct binary format of an executable for a user to download.

Header type Request header, Client hint
Forbidden header name Yes (Sec- prefix)

Syntax

http
Sec-CH-UA-Bitness: <bitness>

Directives

<bitness>

A string indicating the underlying platform architecture bitness, such as: "64", "32".

Examples

Using Sec-CH-UA-Bitness

A server requests the Sec-CH-UA-Bitness header by including Accept-CH in a response to any request from the client, using the name of the desired header as a token:

http
HTTP/1.1 200 OK
Accept-CH: Sec-CH-UA-Bitness

The client may choose to provide the hint, and add the Sec-CH-UA-Bitness header to subsequent requests. For example, on a Windows based 64-bit computer, the client might add the header as shown:

http
GET /GET /my/page HTTP/1.1
Host: example.site

Sec-CH-UA: " Not A;Brand";v="99", "Chromium";v="96", "Google Chrome";v="96"
Sec-CH-UA-Mobile: ?0
Sec-CH-UA-Platform: "Windows"
Sec-CH-UA-Bitness: "64"

Specifications

Specification
User-Agent Client Hints
# sec-ch-ua-bitness

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Sec-CH-UA-Bitness request header
Experimental

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
Experimental. Expect behavior to change in the future.

See also