# Accept-Language header > Advertises the natural languages the client prefers for the response. Source: https://apiguide.dev/headers/accept-language Direction: request Registered: yes Defined in: RFC 9110, Section 12.5.4 Updated: 2026-07-10 ## What is the Accept-Language header? The `Accept-Language` request header tells the server which natural languages the client prefers, using language tags with optional quality (`q`) values to express relative preference. The server uses it during content negotiation to choose a language variant. ## API Usage & Best Practices * **Use q-values to rank**: A weight from `0` to `1` orders preferences, for example `fr-CH, fr;q=0.9, en;q=0.8`. * **Handle unsupported languages**: If no acceptable language can be served, the server may respond with `406 Not Acceptable`, though returning a sensible default is often friendlier. * **Confirm with `Content-Language`**: The chosen variant should be echoed back in the response's `Content-Language` header. ## Examples ```http GET /articles/42 HTTP/1.1 Host: api.example.com Accept-Language: fr-CH, fr;q=0.9, en;q=0.8, *;q=0.5 ```