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)
Sec-CH-UA-Form-Factors: <form-factor>
Sec-CH-UA-Form-Factors: <form-factor>, …, <form-factor><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.
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/1.1 200 OK
Accept-CH: Sec-CH-UA-Form-FactorsThe 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:
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.