Sec-CH-UA-Form-Factors

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

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

The HTTP Sec-CH-UA-Form-Factors request header is a user agent client hint which provides information on the user-agent's device form factor.

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

Syntax

http
Sec-CH-UA-Form-Factors: <form-factor>
Sec-CH-UA-Form-Factors: <form-factor>, …, <form-factor>

Directives

<form-factor>

A string indicating a common device form factor. All applicable form factors can be included. The meanings of the allowed values are:

"Desktop"

A user-agent running on a personal computer.

"Automotive"

A user-agent embedded in a vehicle, where the user may be responsible for operating the vehicle and have limited ability to interact.

"Mobile"

Small, touch-oriented device typically carried on a user's person.

"Tablet"

A touch-oriented device larger than "Mobile" and not typically carried on a user's person.

"XR"

Immersive devices that augment or replace the environment around the user.

"EInk"

A device characterized by slow screen updates and limited or no color resolution.

"Watch"

A mobile device with a tiny screen (typically less than 2 inches), carried in such a way that the user can glance at it quickly.

Examples

Using Sec-CH-UA-Form-Factors

A server requests the Sec-CH-UA-Form-Factors header by including the 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-Form-Factors

The client may choose to provide the hint, and add the Sec-CH-UA-Form-Factors header to subsequent requests. For example, the client might add the header as shown:

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

Sec-CH-UA-Mobile: ?0
Sec-CH-UA-Form-Factors: "EInk"

In this case, "EInk" means that the device is characterized by slow screen updates and limited color resolution, and as such, responses may differ depending on this hint.

Specifications

Specification
User-Agent Client Hints
# sec-ch-ua-form-factors

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-Form-Factors 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