AcceptLanguage
Accept-Language is an HTTP header used by clients to indicate the preferred languages for the response. It informs the server of the user’s language and regional preferences so that the server can perform content negotiation and return a representation in an appropriate language when available.
The header value is a prioritized list of language ranges and optional quality values. Language tags follow
Server behavior centers on content negotiation. The server compares the request’s language ranges against available representations
Practical use notes: user agents (browsers, apps) typically populate Accept-Language from user preferences and system locale.