Sec-CH-UA-Form-Factors

Limited availability

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

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 request header 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

BCD tables only load in the browser

See also