Revision 1106837 of Accept-Language

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<p>The <strong><code>Accept-Language</code></strong> request HTTP header advertises which languages the client is able to understand, and which locale variant is preferred. Using <a href="/en-US/docs/Web/HTTP/Content_negotiation">content negotiation</a>, the server then selects one of the proposal, use it and inform the client of its choice with the {{HTTPHeader("Content-Language")}} response header. Browsers set adequate values for this header according their user interface language and even if a user can change it, this happens rarely (and is frown upon as it leads to fingerprinting).</p>

<p>This header is a hint to be used when the server has no way of determining the language via another way, like a specific URL, that is controlled by an explicit user decision. It is recommended that the server never overrides an explicit decision. The content of the <code>Accept-Language</code> is often out of the control of the user (like when he is traveling and using an Internet Cafe); the user may also want to visit a page in another language than the locale of its user interface.</p>

<p>If the server cannot serve any matching language, it can theoretically send back a {{HTTPStatus("406")}} <code>Not Acceptable</code> error code. But, for UX reason, this is rarely done and the standard way is to ignore the <code>Accept-Language</code> header in this case.</p>

<table class="properties">
 <tbody>
  <tr>
   <th scope="row">Header type</th>
   <td>{{Glossary("Request header")}}</td>
  </tr>
  <tr>
   <th scope="row">{{Glossary("Forbidden header name")}}</th>
   <td>no</td>
  </tr>
 </tbody>
</table>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">
Accept-Language: &lt;language&gt;
Accept-Language: &lt;locale&gt;
Accept-Language: *

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

<h2 id="Directives">Directives</h2>

<dl>
 <dt><code>&lt;language&gt;</code></dt>
 <dd>A language expressed as a 2 or 3-character string</dd>
 <dt><code>&lt;locale&gt;</code></dt>
 <dd>A full language tag. In addition to the language itself, it may contains additional information after a <code>'-'</code>. The most common extra information are the country variant (like <code>'en-US'</code>) or the type of alphabet to use (like <code>'sr-Lat'</code>). Other variant like the type of orthography (<code>'de-DE-1996'</code>) are normally never used in the context of this header</dd>
 <dt><code>*</code></dt>
 <dd>Any language, <code>'*'</code> being used as a wildcard.</dd>
 <dt><code>;q=</code> (q-factor weighting)</dt>
 <dd>Any value used is placed in an order of preference expressed using relative <a href="/en-US/docs/Glossary/Q-factor">quality factor</a> called the <em>weight</em>.</dd>
</dl>

<h2 id="Examples">Examples</h2>

<pre>
Accept-Language: de

Accept-Language: de-CH

Accept-Language: en-US,en;q=0.5
</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Title</th>
  </tr>
  <tr>
   <td>{{RFC("7232", "Accept-Language", "5.3.5")}}</td>
   <td>Hypertext Transfer Protocol (HTTP/1.1): Semantics and Context</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p class="hidden">The compatibility table in this page is generated from structured data. If you’d like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data/README.md">https://github.com/mdn/browser-compat-data/README.md</a> and send us a pull request.</p>

<p>{{Compat}}</p>

<h2 id="See_also">See also</h2>

<ul>
 <li>HTTP <a href="/en-US/docs/Web/HTTP/Content_negotiation">content negotiation</a></li>
 <li>Header with the result of the content negotiation: {{HTTPHeader("Content-Language")}}</li>
 <li>Other similar headers: {{HTTPHeader("TE")}}, {{HTTPHeader("Accept-Encoding")}}, {{HTTPHeader("Accept-Charset")}}, {{HTTPHeader("Accept")}}</li>
</ul>