Support Sec-CH-UA-Form-Factor

[nielsbasjes]

This website https://github.com/WICG/ua-client-hints mentions:

The Sec-CH-UA-Form-Factor header field represents the form-factor of a device, historically represented as a <deviceCompat> token in the User-Agent string (e.g., "Tablet", "VR", etc.)

For example:

Sec-CH-UA-Form-Factor: "XR"

https://wicg.github.io/ua-client-hints/#sec-ch-ua-form-factor

3.4. The 'Sec-CH-UA-Form-Factor' Header Field
The Sec-CH-UA-Form-Factor request header field gives a server information about the user agent's form-factor. It is a Structured Header whose value MUST be a string. Its value SHOULD match one of the following common form-factor values: "Automotive", "Mobile", "Tablet", "TV", "VR", "XR", "Unknown" or the empty string. [RFC8941].

NOTE: A "desktop" form-factor would be represented by the empty string.

The header’s ABNF is:

Sec-CH-UA-Form-Factor = sf-string

[nielsbasjes]

Initial changes https://github.com/nielsbasjes/yauaa/tree/SecChUaFormFactor

Currently some of the values are unclear to me.

See also WICG/ua-client-hints#333

[nielsbasjes]

The field is supported.
Because there are no browsers yet that have it there are no rules yet that can do anything with it.