Accept-Language

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The HTTP Accept-Language request header indicates the natural language and locale that the client prefers. The server uses content negotiation to select one of the proposals and informs the client of the choice with the Content-Language response header. Browsers set required values for this header according to their active user interface language. Users can also configure additional preferred languages through browser settings.

The Accept-Language header generally lists the same locales as the navigator.languages property, with decreasing q values (quality values). Some browsers, like Chrome and Safari, add language-only fallback tags in Accept-Language. For example, en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7 when navigator.languages is ["en-US", "zh-CN"]. For privacy purposes (reducing fingerprinting), both Accept-Language and navigator.languages may not include the full list of user preferences. For example, in Safari (always) and Chrome's incognito mode, only one language is listed.

This header serves as a hint when the server cannot determine the target content language otherwise (for example, use a specific URL that depends on an explicit user decision). The server should never override an explicit user language choice. The content of Accept-Language is often out of a user's control (when traveling, for instance). A user may also want to visit a page in a language different from the user interface language.

The server may send back a 406 Not Acceptable error code when unable to serve content in a matching language, but this is rarely implemented. Servers often ignore the Accept-Language header in such cases and send a successful response with the most appropriate resource instead for a better user experience.

Header type	Request header
Forbidden header name	No
CORS-safelisted request header	Yes*

* Values can only be 0-9, A-Z, a-z, space, or the characters *,-.;=.

Syntax

http

Accept-Language: <language>
Accept-Language: *

// Multiple types, weighted with the quality value syntax:
Accept-Language: fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5

Directives

<language>: A language tag (which is sometimes referred to as a "locale identifier"). This consists of a 2-3 letter base language tag that indicates a language, optionally followed by additional subtags separated by -. The most common extra information is the country or region variant (like en-US or fr-CA) or the type of alphabet to use (like sr-Latn). Other variants, like the type of orthography (de-DE-1996), are usually not used in the context of this header.
* (wildcard): Any language not matched by any other language present in the Accept-Language field.
;q= (q-factor weighting): Any value placed in an order of preference expressed using a relative quality value called weight. The quality value defaults to 1.

Examples

Using Accept-Language headers

The following request has a preference for German using the de base language:

http

Accept-Language: de

Using quality values in Accept-Language

The following request indicates a stronger preference for Danish, but accepts British English and other types of English at a lower priority:

http

Accept-Language: da, en-gb;q=0.8, en;q=0.7

Specifications

Specification
HTTP Semantics # field.accept-language

Browser compatibility

BCD tables only load in the browser