The MediaDevices.getUserMedia()
method prompts the user for permission to use one video and/or one audio input device such as a camera or screensharing and/or a microphone. If the user provides permission, then the returned Promise
is resolved with the resulting MediaStream
object. If the user denies permission, or media is not available, then the promise is rejected with PermissionDeniedError
or NotFoundError
respectively. Note that it is possible for the returned promise to neither resolve nor reject, as the user is not required to make a choice.
Syntax
var gumPromise = MediaDevices.getUserMedia(constraints);
Generally, you will access the MediaDevices
singleton object using navigator.mediaDevices
, like this:
navigator.mediaDevices.getUserMedia(myConstraints).then(function(mediaStream) { /* use the stream */ }).catch(function(err) { /* handle the error */ });
Parameters
constraints
-
Is a
MediaStreamConstraints
object specifying the types of media to request, along with any requirements for each type.The constraints parameter is a
MediaStreamConstraints
object with two members:video
andaudio
, describing the media types requested. Either or both must be specified. If the browser cannot find all media tracks with the specified types that meet the constraints given, then the returned promise is rejected withNotFoundError
.The following requests both audio and video without any specific requirements:
{ audio: true, video: true }
If
true
is specified for a media type, the resulting stream is required to have that type of track in it. If one cannot be included for any reason, the call togetUserMedia()
will result in an error.While information about a user's cameras and microphones are inaccessible for privacy reasons, an application can request the camera and microphone capabilities it needs and wants, using additional constraints. The following expresses a preference for 1280x720 camera resolution:
{ audio: true, video: { width: 1280, height: 720 } }
The browser will try to honor this, but may return other resolutions if an exact match is not available, or the user overrides it.
To require a capability, use the keywords
min
,max
, orexact
(a.k.a. min == max). The following demands a minimum resolution of 1280x720:{ audio: true, video: { width: { min: 1280 }, height: { min: 720 } } }
If no camera exists with this resolution or higher, then the returned promise will be rejected with
NotFoundError
, and the user will not be prompted.The reason for the difference in behavior is that the keywords
min
,max
, andexact
are inherently mandatory, whereas plain values and a keyword calledideal
are not. Here's a fuller example:{ audio: true, video: { width: { min: 1024, ideal: 1280, max: 1920 }, height: { min: 776, ideal: 720, max: 1080 } } }
An
ideal
value, when used, has gravity, which means that the browser will try to find the setting (and camera, if you have more than one), with the smallest fitness distance from the ideal values given.Plain values are inherently ideal, which means that the first of our resolution examples above could have been written like this:
{ audio: true, video: { width: { ideal: 1280 }, height: { ideal: 720 } } }
Not all constraints are numbers. For example, on mobile devices, the following will prefer the front camera (if one is available) over the rear one:
{ audio: true, video: { facingMode: "user" } }
To require the rear camera, use:
{ audio: true, video: { facingMode: { exact: "environment" } } }
Return value
A Promise
whose fulfillment handler receives a MediaStream
object when the requested media has successfully been obtained.
Errors
Rejections of the returned promise are made by passing a DOMException
error object to the promise's failure handler. Possible errors are:
AbortError
- Although the user and operating system both granted access to the hardware device, and no hardware issues occurred that would cause a
NotReadableError
, some problem occurred which prevented the device from being used. NotAllowedError
- The user has specified that the current browsing instance is not permitted access to the device; or the user has denied access for the current session; or the user has denied all access to user media devices globally.
Older versions of the specification used
SecurityError
for this instead;SecurityError
has taken on a new meaning. NotFoundError
- No media tracks of the type specified were found that satisfy the given constraints.
NotReadableError
- Although the user granted permission to use the matching devices, a hardware error occurred at the operating system, browser, or Web page level which prevented access to the device.
OverConstrainedError
- The specified constraints resulted in no candidate devices which met the criteria requested. The error is an object of type
OverconstrainedError
, and has aconstraint
property whose string value is the name of a constraint which was impossible to meet, and amessage
property containing a human-readable string explaining the problem.Because this error can occur even when the user has not yet granted permission to use the underlying device, it can potentially be used as a fingerprinting surface. SecurityError
- User media support is disabled on the
Document
on whichgetUserMedia()
was called. The mechanism by which user media support is enabled and disabled is left up to the individual user agent. TypeError
- The list of constraints specified is empty, or has all constraints set to
false
.
Examples
Width and height
This example gives a preference for camera resolution, and assigns the resulting MediaStream
object to a video element.
// Prefer camera resolution nearest to 1280x720. var constraints = { audio: true, video: { width: 1280, height: 720 } }; navigator.mediaDevices.getUserMedia(constraints) .then(function(mediaStream) { var video = document.querySelector('video'); video.srcObject = mediaStream; video.onloadedmetadata = function(e) { video.play(); }; }) .catch(function(err) { console.log(err.name + ": " + err.message); }); // always check for errors at the end.
Using the new API in older browsers
Here's an example of using navigator.mediaDevices.getUserMedia()
, with a polyfill to cope with older browsers. Note that this polyfill does not correct for legacy differences in constraints syntax, which means constraints won't work well across browsers. It is recommended to use the adapter.js polyfill instead, which does handle constraints.
// Older browsers might not implement mediaDevices at all, so we set an empty object first if (navigator.mediaDevices === undefined) { navigator.mediaDevices = {}; } // Some browsers partially implement mediaDevices. We can't just assign an object // with getUserMedia as it would overwrite existing properties. // Here, we will just add the getUserMedia property if it's missing. if (navigator.mediaDevices.getUserMedia === undefined) { navigator.mediaDevices.getUserMedia = function(constraints) { // First get ahold of the legacy getUserMedia, if present var getUserMedia = (navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia); // Some browsers just don't implement it - return a rejected promise with an error // to keep a consistent interface if (!getUserMedia) { return Promise.reject(new Error('getUserMedia is not implemented in this browser')); } // Otherwise, wrap the call to the old navigator.getUserMedia with a Promise return new Promise(function(resolve, reject) { getUserMedia.call(navigator, constraints, resolve, reject); }); } } navigator.mediaDevices.getUserMedia({ audio: true, video: true }) .then(function(stream) { var video = document.querySelector('video'); // Older browsers may not have srcObject video.src = window.URL.createObjectURL(stream); video.onloadedmetadata = function(e) { video.play(); }; }) .catch(function(err) { console.log(err.name + ": " + err.message); });
Frame rate
Lower frame-rates may be desirable in some cases, like WebRTC transmissions with bandwidth restrictions.
var constraints = { video: { frameRate: { ideal: 10, max: 15 } } };
Front and back camera
On mobile phones.
var front = false; document.getElementById('flip-button').onclick = function() { front = !front; }; var constraints = { video: { facingMode: (front? "user" : "environment") } };
Permissions
To use getUserMedia()
in an installable app (for example, a Firefox OS app), you need to specify one or both of the following fields inside your manifest file:
"permissions": { "audio-capture": { "description": "Required to capture audio using getUserMedia()" }, "video-capture": { "description": "Required to capture video using getUserMedia()" } }
See permission: audio-capture and permission: video-capture for more information.
Specifications
Specification | Status | Comment |
---|---|---|
Media Capture and Streams The definition of 'MediaDevices.getUserMedia()' in that specification. |
Editor's Draft | Initial definition |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Microsoft Edge | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|---|
Basic support | 53.0[1][3] | 36 (36) [2] | ? | No support | 40[1] | No support |
Promises | 53.0 | 38 (38) | ? | No support | ? | No support |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|
Basic support | No support | 53.0[1][3] | 36.0 (36) [2] | No support | 40[1] | No support | 53.0[1][3] |
Promises | No support | 53.0 | 38.0 (38) | No support | ? | No support | 53.0 |
[1] Older versions of Chrome and Opera implement navigator.webkitGetUserMedia
, the prefixed version of the legacy navigator.getUserMedia
method.
From version 47 to 52, the promise-based interface was only available through the adapter.js polyfill, or using the flag chrome://flags/#enable-experimental-web-platform-features. Starting with version 53, the promise-based interface is on by default, though that interface is still not available through navigator
.
[2] Older versions of Firefox implement navigator.mozGetUserMedia
, the prefixed version of the legacy navigator.getUserMedia
method.
The promise-based version of this method and the constraint syntax described here are available as of Firefox 38. Earlier versions (32-37) used an outdated constraint syntax, but the syntax described here, as well as the promise-based interface, is available there through the adapter.js polyfill.
Firefox 49 includes changes to bring the possible errors up to date with the specification, including the change to the meaning of SecurityError
.
Opera uses an outdated constraint syntax, but the syntax described here is available through the adapter.js polyfill.
[3] Chrome throws error if the page serving the script is loaded from insecure origin (i.e. HTTP).
See also
- The older navigator.getUserMedia legacy API.
- navigator.enumerateDevices - learn the types and number of devices the user has available.
- WebRTC - the introductory page to the API
- MediaStream API - the API for the media stream objects
- Taking webcam photos - a tutorial on using
getUserMedia() for taking photos rather than video.