Revision 1131805 of MediaTrackConstraints.deviceId

<div>{{APIRef("Media Capture and Streams")}}</div>

<p>The {{domxref("MediaTrackConstraints")}} dictionary's <code><strong>deviceId</strong></code> property is a {{domxref("ConstrainDOMString")}} describing the requested or mandatory constraints placed upon the value of the {{domxref("MediaTrackSettings.deviceId", "deviceId")}} constrainable property.</p>

<p>If needed, you can determine whether or not this constraint is supported by checking the value of {{domxref("MediaTrackSupportedConstraints.deviceId")}} as returned by a call to {{domxref("MediaDevices.getSupportedConstraints()")}}. However, typically this is unnecessary since browsers will simply ignore any constraints they're unfamiliar with.</p>

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

<pre class="syntaxbox">
var <em>constraintsObject</em> = { deviceId: <em>constraint</em> };

<em>constraintsObject</em>.deviceId = <em>constraint</em>;
</pre>

<h3 id="Value">Value</h3>

<p>An object based on {{domxref("ConstrainDOMString")}} specifying one or more acceptable, ideal, and/or exact (mandatory) device IDs which are acceptable as the source of media content.</p>

<p>Device IDs are unique for a given origin, and are guaranteed to be valid across browsing sessions on the same origin. However, the value of the deviceId is determined by the source of the track's content, and there's no particular format mandated by the specification (although some kind of GUID is recommended). That means that a given track will only return one value for the <code>deviceId</code> when you call {{domxref("MediaStreamTrack.getCapabilities", "getCapabilities()")}}</p>

<p>Because of this, there's no use for the device ID when calling {{domxref("MediaStreamTrack.applyConstraints()")}}, since there is only one possible value; however, you can record a <code>deviceId</code> and use it to ensure that you get the same source for multiple calls to {{domxref("MediaDevices.getUserMedia", "getUserMedia()")}}.</p>

<h2 id="Example" name="Example">Example</h2>

<p>See {{SectionOnPage("/en-US/docs/Web/API/Media_Streams_API/Constraints", "Example: Constraint exerciser")}} for an example.</p>

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

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{ SpecName('Media Capture', '#widl-MediaTrackConstraints-deviceId', 'deviceId') }}</td>
   <td>{{ Spec2('Media Capture') }}</td>
   <td>Initial specification.</td>
  </tr>
 </tbody>
</table>

<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>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{ CompatGeckoDesktop(50) }}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatVersionUnknown}}</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>Android Webview</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{ CompatGeckoMobile(50) }}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

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

<ul>
 <li><a href="/en-US/docs/Web/API/Media_Streams_API">Media Capture and Streams API</a></li>
 <li><a href="/en-US/docs/Web/API/Media_Streams_API/Constraints">Capabilities, constraints, and settings</a></li>
 <li>{{domxref("MediaTrackConstraints")}}</li>
 <li>{{domxref("MediaDevices.getSupportedConstraints()")}}</li>
 <li>{{domxref("MediaTrackSupportedConstraints")}}</li>
 <li>{{domxref("MediaStreamTrack")}}</li>
</ul>