Specifies the language that the intended audience should be able to speak.
This header indicates the language that the audience for this page should be familiar with. It usually indicates the language that the page is written in, but not necessarily.
If this field is blank, then it means the webpage is intended for all languages. To specific the audience's language, set this to an ISO 639 language code, with multiple languages separated by commas.
For more information, please read the documentation on MDN Web Docs.
Ready to validate your website to check for this header and 100+ others important tests?