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var appliedPromise = MediaStreamTrack.applyConstraints(constraints);


constraints 可选
A MediaTrackConstraints object listing the constraints to apply to the track's constrainable properties; any existing constraints are replaced with the new values specified, and any constrainable properties not included are restored to their default constraints. If this parameter is omitted, all currently set custom constraints are cleared. This object represents the basic set of constraints that must apply for the Promise to resolve. The object may contain an advanced property containing an array of additional MediaTrackConstrants objects, which are treated as exact requires. 

Return value

A Promise which resolves when the constraints have been successfully applied. If the constraints cannot be applied, the promise is rejected with a MediaStreamError whose name is OverconstrainedError, to indicate that the constraints could not be met. This can happen if the specified constraints are too strict to find a match when attempting to configure the track.


The following shows how to specify a basic and advanced set of constraints. It specifies that the page or web app needs a width between 640 and 1280 and a height between 480 and 720, with the later number in each pair being preferred. The advanced property further specifies that an image size of 1920 by 1280 is the preferred or an aspect ratio of 1.333 if that is not available. Note that these constraints also illustrate what the spec refers to as a backoff strategy.

const constraints = {
  width: {min: 640, ideal: 1280},
  height: {min: 480, ideal: 720},
  advanced: [
    {width: 1920, height: 1280},
    {aspectRatio: 1.333}

navigator.mediaDevices.getUserMedia({ video: true })
.then(mediaStream => {
  const track = mediaStream.getVideoTracks()[0];
  .then(() => {
    // Do something with the track such as using the Image Capture API.
  .catch(e => {
    // The constraints could not be satisfied by the available devices.


Specification Status Comment
Media Capture and Streams
Candidate Recommendation Initial definition.
MediaStream Image Capture
Working Draft Adds image constraints.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
applyConstraintsChrome Full support 63Edge Full support 12Firefox Full support 50IE No support NoOpera Full support 46Safari Full support YesWebView Android Full support 63Chrome Android Full support 63Firefox Android Full support 50Opera Android Full support 43Safari iOS Full support YesSamsung Internet Android Full support 7.0


Full support  
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See also