jsx_a11y/lang Correctness
What it does
The lang prop on the <html> element must be a valid IETF's BCP 47 language tag.
Why is this bad?
If the language of a webpage is not specified as valid, the screen reader assumes the default language set by the user. Language settings become an issue for users who speak multiple languages and access website in more than one language.
Examples
Examples of incorrect code for this rule:
jsx
<html>
<html lang="foo">Examples of correct code for this rule:
jsx
<html lang="en">
<html lang="en-US">