We intend to deprecate PaymentAddress.languageCode, which is browser's best guess for the language of the text in the shipping, billing, delivery, or pickup address in Payment Request API.
The language of an address text is useful for choosing the right address formatting rules, but determining the language of any text can be done without user agent help. A W3C review of Chrome's existing language guessing heuristics revealed they were subpar.
Firefox: Removed languageCode.
Edge: No public signals
Safari: Removed languageCode.
Web developers: No signals
Usage counter for languageCode shows no usage of this field on the web.
Ongoing technical constraints
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)? Yes or no.
OWP launch tracking bug
Requesting approval to remove?
No. Going to add a deprecation warning first, wait a couple of months, then will request approval to remove here.