Revision 1097513 of Host

<div>{{HTTPSidebar}}</div>

<p>The <code><strong>Host</strong></code> request header specifies the domain name of the server (for virtual hosting), and (optionally) the TCP port number on which the server is listening.</p>

<p>If no port is given, the default port for the service requested (e.g., "80" for an HTTP URL) is implied.</p>

<p>A <code>Host</code> header field must be sent in all HTTP/1.1 request messages. A {{HTTPStatus("400")}} (Bad Request) status code will be sent to any HTTP/1.1 request message that lacks a <code>Host</code> header field or contains more than one.</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>yes</td>
  </tr>
 </tbody>
</table>

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

<pre class="syntaxbox">
Host: &lt;host&gt;:&lt;port&gt;
</pre>

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

<dl>
 <dt>&lt;host&gt;</dt>
 <dd>the domain name of the server (for virtual hosting).</dd>
 <dt>&lt;port&gt; {{optional_inline}}</dt>
 <dd>TCP port number on which the server is listening.</dd>
</dl>

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

<pre>
Host: developer.cdn.mozilla.net</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("7230", "Host", "5.4")}}</td>
   <td>Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing</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>{{HTTPStatus("400")}}</li>
</ul>