The guideline
Put a lang attribute on the html element of every page, holding a well-formed BCP 47 language tag for the language the page mainly uses (for example en, fr or pt-BR). Make it match the text: a translated page needs its own value, so a template must not leave lang="en" on a German page. On a site in several languages, each language version declares its own. Where a page mixes languages, declare the one used most.
Common failures
- The page does not declare its language correctly: the lang attribute is missing, empty, malformed, or names a different language from the text.
Where it applies
Where
Disciplines
Devices
Why it matters, how to fix it, and the research behind it
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