Does lang attribute or heuristics affect automatic translation?

[mitchellevan]

Firefox translation 2024-10-25 said it can't translate Japanese yet.

• Does it look at the lang attribute for this?
• Can I find a web page in a language that Firefox can't even name? It could be my test pages

Another example: Android Chrome on 2024-12-29 offered to translate French on my en.html demo page. The page has lang="en" and it has a section with lang="es" and a section with lang="fr". I took a screenshot on the device.