Revision 997319 of WebSockets

<p>{{DefaultAPISidebar("Websockets API")}}</p>

<p><strong>WebSockets</strong> is an advanced technology that makes it possible to open an interactive communication session between the user's browser and a server. With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply.</p>

<h2 id="Interfaces">Interfaces</h2>

<dl>
 <dt><a href="/en-US/docs/Web/API/WebSocket" title="en/WebSockets/WebSockets reference/WebSocket"><code>WebSocket</code></a></dt>
 <dd>The primary interface for connecting to a WebSocket server and then sending and receiving data on the connection.</dd>
 <dt><code><a href="/en-US/docs/Web/API/CloseEvent" title="en/WebSockets/WebSockets reference/CloseEvent">CloseEvent</a></code></dt>
 <dd>The event sent by the WebSocket object when the connection closes.</dd>
 <dt><a href="/en-US/docs/Web/API/MessageEvent" title="en/WebSockets/WebSockets reference/MessageEvent"><code>MessageEvent</code></a></dt>
 <dd>The event sent by the WebSocket object when a message is received from the server.</dd>
</dl>

<h2 class="Tools" id="Tools" name="Tools">Tools</h2>

<p>&nbsp;</p>

<ul>
 <li><a class="external" href="https://socket.io" title="https://socket.io/">Socket.IO</a>: A powerful cross-platform WebSocket API for <a class="external" href="https://nodejs.org" title="https://nodejs.org/">Node.js</a>.</li>
 <li><a class="link-https" href="https://github.com/Worlize/WebSocket-Node" title="https://github.com/Worlize/WebSocket-Node">WebSocket-Node</a>: A WebSocket server API implementation for <a class="external" href="https://nodejs.org" title="https://nodejs.org/">Node.js</a>.</li>
 <li><a href="https://www.totaljs.com">Total.js</a>: Web application framework for <a href="https://www.nodejs.org">Node.js</a>&nbsp;(Example: <a href="https://github.com/totaljs/examples/tree/master/websocket">WebSocket chat</a>)</li>
 <li><a href="https://www.npmjs.com/package/faye-websocket">Faye</a>: A <a href="https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API">WebSocket</a>&nbsp;(two-ways connections) and <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventSource/">EventSource</a>&nbsp;(one-way connections) for <a class="external" href="https://nodejs.org" title="https://nodejs.org/">Node.js</a>&nbsp;Server and Client.</li>
 <li><a href="https://ajf.me/websocket/#libs" title="https://websocket.us/#libs">A more extensive list of frameworks and libraries here</a></li>
</ul>

<h2 class="Related_Topics" id="Related_Topics" name="Related_Topics">Related Topics</h2>

<ul>
 <li><a href="/en-US/docs/AJAX" title="AJAX">AJAX</a>, <a href="/en-US/docs/JavaScript" title="JavaScript">JavaScript</a></li>
</ul>

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

<ul>
 <li><a class="external" href="https://tools.ietf.org/html/rfc6455">RFC 6455 - The WebSocket Protocol</a></li>
 <li><a class="external" href="https://www.w3.org/TR/websockets/">WebSocket API Specification</a></li>
 <li><a href="/en-US/docs/Server-sent_events" title="Server-sent_events">Server-Sent Events</a></li>
</ul>

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

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Version -76 support {{obsolete_inline}}</td>
   <td>6</td>
   <td>{{CompatGeckoDesktop("2.0")}}</td>
   <td>{{CompatNo}}</td>
   <td>11.00 (disabled)</td>
   <td>5.0.1</td>
  </tr>
  <tr>
   <td>Protocol version 7 support {{obsolete_inline}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatGeckoDesktop("6.0")}}<br />
    {{property_prefix("Moz")}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
  <tr>
   <td>Protocol version 10 support {{obsolete_inline}}</td>
   <td>14</td>
   <td>{{CompatGeckoDesktop("7.0")}}<br />
    {{property_prefix("Moz")}}</td>
   <td>HTML5 Labs</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Standard - RFC 6455 Support</td>
   <td>16</td>
   <td>{{CompatGeckoDesktop("11.0")}}</td>
   <td>10</td>
   <td>12.10</td>
   <td>6.0</td>
  </tr>
  <tr>
   <td>Usable in Workers</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop("37.0")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Version -76 support {{obsolete_inline}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Protocol version 7 support {{obsolete_inline}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Protocol version 8 support (IETF draft 10) {{obsolete_inline}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatGeckoMobile("7.0")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Standard - RFC 6455 Support</td>
   <td>4.4</td>
   <td>{{CompatGeckoDesktop("11.0")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>12.10</td>
   <td>6.0</td>
  </tr>
  <tr>
   <td>Usable in Workers</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoMobile("37.0")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h3 id="Gecko_notes">Gecko notes</h3>

<p>WebSockets support in Firefox is continuing to track the evolving WebSocket specification. Firefox 6 implements version 7 of the underlying protocol, while Firefox 7 implements version 8 (as specified by IETF draft 10). Firefox mobile received WebSocket support in Firefox mobile 7.0.</p>

<h4 id="Gecko_6.0">Gecko 6.0</h4>

<p>Prior to Gecko 6.0 {{geckoRelease("6.0")}}, there was, incorrectly, a <code>WebSocket</code> object that some sites were thinking implied that <code>WebSocket</code> services were not prefixed; this object has been renamed to <code>MozWebSocket</code>.</p>

<h4 id="Gecko_7.0">Gecko 7.0</h4>

<p>Starting in Gecko 7.0 {{geckoRelease("7.0")}}, the <code>network.websocket.max-connections</code> preference is used to determine the maximum number of WebSocket connections that can be open at a time. The default value is 200.</p>

<h4 id="Gecko_8.0">Gecko 8.0</h4>

<p>Starting in Gecko 8.0 {{geckoRelease("8.0")}}, the deflate-stream extension to the WebSocket protocol has been disabled, since it's been deprecated from the specification drafts. This resolves incompatibilities with some sites.</p>

<h4 id="Gecko_11.0">Gecko 11.0</h4>

<p>Prior to Gecko 11.0, both incoming and outgoing messages were limited to 16 MB in size. They may now be up to 2 GB in size. Note, however, that memory limitations (especially on mobile devices) make that a theoretical maximum, not a practical one. In reality, transfers of that size will fail on devices that don't have enough memory.</p>

<p>Additionally, ArrayBuffer send and receive support for binary data has been implemented.</p>

<p>Starting in Gecko 11.0, the WebSocket API is no longer prefixed.</p>