lang and xml:lang values must match
WCAG 3.1.1
Language of Page Accessibility isn’t only about avoiding violations — it’s about ensuring your product can be used confidently by everyone. This guide explains the principle of this rule, shows what goes wrong in real-world code, and provides a verified fix that meets WCAG and the European Accessibility Act (EAA).
Why this matters and how to fix it
Why this matters
Correct language declarations ensure proper pronunciation and processing by assistive technologies.
How to fix this issue
Set `lang` (and `xml:lang` where present) to the correct primary language of the page and keep them in sync.
Automated detection · Manual review recommended
Developer guidance
Drive language from a single locale source. Validate with the W3C Internationalization Checker in CI.
Code examples
Incorrect Implementation
<html lang="en" xml:lang="fr">…</html>Correct Implementation
<html lang="en" xml:lang="en">…</html>
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