# jsx-a11y/lang <!-- end auto-generated rule header --> The `lang` prop on the `<html>` element must be a valid IETF's BCP 47 language tag. ## Rule details This rule takes no arguments. ### Succeed ```jsx <html lang="en"> <html lang="en-US"> ``` ### Fail ```jsx <html> <html lang="foo"> ``` ## Accessibility guidelines - [WCAG 3.1.1](https://www.w3.org/WAI/WCAG21/Understanding/language-of-page) ### Resources - [axe-core, valid-lang](https://dequeuniversity.com/rules/axe/3.2/valid-lang) - [Language tags in HTML and XML](https://www.w3.org/International/articles/language-tags/) - [IANA Language Subtag Registry](https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry)