Use valid language codes in the `lang` attribute
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
Assistive technologies depend on standardized language codes to apply correct pronunciation and braille translation rules. Invalid or misspelled codes can cause screen readers to fall back to the wrong voice profile.
How to fix this issue
Use valid BCP 47 language codes (e.g., `en`, `en-US`, `sv-SE`, `fr-FR`). Avoid custom or incomplete tags like `english` or `us-en`.
Developer guidance
Validate all `lang` attributes using a linter or accessibility testing tool. Maintain a locale map if your app supports multiple languages.
Code examples
Incorrect Implementation
<html lang='english'>Correct Implementation
<html lang='en'>
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