The lang prop on the <html> element must be a valid IETF's BCP 47 language tag.
This rule takes no arguments.
```jsx
``` ### Fail ```jsx ``` ## 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)