SEO checks / Internationalization
Declared <html lang> does not match the language of the text
What this means
The document declares one language in <html lang> while the body copy reads as another. A wrong lang attribute misdirects screen readers, browser translation prompts and hreflang clustering. NOTE: the detector behind this check is deliberately narrow — it scores function words for English, Spanish, French, German, Portuguese, Italian and Dutch only, needs at least 50 words, and stays silent unless one language wins by a factor of two. It cannot see any other language, and it will say nothing rather than guess.
How to fix it
Set <html lang> to the BCP 47 tag the page is actually written in. If the page genuinely mixes languages, tag the document with its primary language and mark the inline exceptions with their own lang attributes.
Fix effort
This check needs review: the change can be drafted for you, but a person has to approve the wording or choose the target before it ships.
Authoritative source
https://developers.google.com/search/docs/specialty/international/localized-versions
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