:focus-visible is now in the HTML standard, replacing :focus in the default user agent style sheet: https://html.spec.whatwg.org/multipage/rendering.html#phrasing-content-3

Thanks Emilio Cobos for the PR: https://github.com/whatwg/html/pull/6256

This is part of the work Igalia has been doing related to adding :focus-visible support in WebKit.