ThegetUserMedia() method of theMediaDevices interface prompts the user for permission to use a media input which produces aMediaStream with tracks containing the requested types of media.

That stream can include, for example, a video track (produced by either a hardware or virtual video source such as a camera, video recording device, screen sharing service, and so forth), an audio track (similarly, produced by a physical or virtual audio source like a microphone, A/D converter, or the like), and possibly other track types.

It returns aPromise that resolves to aMediaStream object.If the user denies permission, or matching media is not available, then the promise is rejected withNotAllowedError orNotFoundErrorDOMException respectively.

Syntax

getUserMedia(constraints)

Parameters

constraints

An object specifying the types of media to request, along with any requirements for each type.

Theconstraints parameter is an 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 withNotFoundErrorDOMException.

For bothvideo andaudio, its value is either a boolean or an object.The default value isfalse.

• Iftrue is specified for a media type, the resulting stream isrequired to have that type of track in it.If one cannot be included for any reason, the returned promise will reject.
• Iffalse is specified for a media type, the resulting streammust not have that type of track, or the returned promise will reject.Because bothvideo andaudio default tofalse, if theconstraints object contains neither property or if it's not present at all, the returned promise will always reject.
• If an object is specified for a media type, the object is read as aMediaTrackConstraints dictionary.

Return value

APromise whose fulfillment handler receives aMediaStream object when the requested media has successfully been obtained.

Exceptions

AbortErrorDOMException

Although the user and operating system both granted access to the hardware device, and no hardware issues occurred that would cause aNotReadableErrorDOMException, throw if some problem occurred which prevented the device from being used.

InvalidStateErrorDOMException

Thrown if current document is not fully active.

NotAllowedErrorDOMException

Thrown if one or more of the requested source devices cannot be used at this time.This will happen if the browsing context is insecure (that is, the page was loaded using HTTP rather than HTTPS).It also happens if the user has specified that the current browsing instance is not permitted access to the device, the user has denied access for the current session, or the user has denied all access to user media devices globally.On browsers that support managing media permissions withPermissions Policy, this error is returned if Permissions Policy is not configured to allow access to the input source(s).

Note:Older versions of the specification usedSecurityError for this instead;SecurityError has taken on a new meaning.

NotFoundErrorDOMException

Thrown if no media tracks of the type specified were found that satisfy the given constraints.

NotReadableErrorDOMException

Thrown if, 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.

OverconstrainedErrorDOMException

Thrown if the specified constraints resulted in no candidate devices which met the criteria requested.The error is an object of typeOverconstrainedError, 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.

Note: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 afingerprinting surface.

SecurityErrorDOMException

Thrown if user media support is disabled on theDocument on whichgetUserMedia() was called.The mechanism by which user media support is enabled and disabled is left up to the individual user agent.

TypeError

Thrown if the list of constraints specified is empty, or has all constraints set tofalse.This can also happen if you try to callgetUserMedia() in an insecure context, sincenavigator.mediaDevices isundefined in an insecure context.

Privacy and security

As an API that may involve significant privacy concerns,getUserMedia()'s specification lays out a wide array of privacy and security requirements that browsers are obligated to meet.

getUserMedia() is a powerful feature that can only be used insecure contexts; in insecure contexts,navigator.mediaDevices isundefined, preventing access togetUserMedia().A secure context is, in short, a page loaded using HTTPS or thefile:/// URL scheme, or a page loaded fromlocalhost.

In addition, user permission is always required to access the user's audio and video inputs.Only a window's top-level document context for a valid origin can even request permission to usegetUserMedia(), unless the top-level context expressly grants permission for a given<iframe> to do so usingPermissions Policy.Otherwise, the user will never even be asked for permission to use the input devices.

For additional details on these requirements and rules, how they are reflected in the context in which your code is running, and about how browsers manage user privacy and security issues, read on.

User privacy

As an API that may involve significant privacy concerns,getUserMedia() is held by the specification to very specific requirements for user notification and permission management.First,getUserMedia() must always get user permission before opening any media gathering input such as a webcam or microphone.Browsers may offer a once-per-domain permission feature, but they must ask at least the first time, and the user must specifically grant ongoing permission if they choose to do so.

Of equal importance are the rules around notification.Browsers are required to display an indicator that shows that a camera or microphone is in use, above and beyond any hardware indicator that may exist.They must also show an indicator that permission has been granted to use a device for input, even if the device is not actively recording at the moment.

For example in Firefox, the URL bar displays a pulsing red icon to indicate that recording is underway.The icon is gray if the permission is in place but recording is not currently underway.The device's physical light is used to indicate whether or not recording is currently active.If you've muted your camera (so-called "facemuting"), your camera's activity light goes out to indicate that the camera is not actively recording you, without discarding the permission to resume using the camera once muting is over.

Security

There are a number of ways security management and controls in auser agent can causegetUserMedia() to return a security-related error.

Permissions Policy

The twoPermissions Policy directives that apply togetUserMedia() arecamera andmicrophone.

For example, this HTTP header will enable use of a camera by the document and any embedded<iframe> elements that are loaded from the same origin:

Permissions-Policy: camera=(self)

This will request access to the microphone for the current origin and the specific originhttps://developer.mozilla.org:

Permissions-Policy: microphone=(self "https://developer.mozilla.org")

If you're usinggetUserMedia() within an<iframe>, you can request permission just for that frame, which is clearly more secure than requesting a more general permission.Here, indicate we need the ability to use both camera and microphone:

<iframe src="https://mycode.example.net/etc" allow="camera; microphone"></iframe>

Encryption based security

ThegetUserMedia() method is only available insecure contexts.A secure context is one the browser is reasonably confident contains a document which was loaded securely, using HTTPS/TLS, and has limited exposure to insecure contexts.If a document isn't loaded in a secure context, thenavigator.mediaDevices property isundefined, making access togetUserMedia() impossible.

Attempting to accessgetUserMedia() in this situation will result in aTypeError.

Document source security

Because of the obvious security concern associated withgetUserMedia() if used unexpectedly or without security being carefully managed, it can only be used in secure contexts.There are a number of insecure ways to load a document that might, in turn, attempt to callgetUserMedia().The following are examples of situations in whichgetUserMedia() is not permitted to be called:

• A document loaded into a sandboxed<iframe> element cannot callgetUserMedia() unless the<iframe> has itssandbox attribute set toallow-same-origin.
• A document loaded using adata:// orblob:// URL which has no origin (such as when one of these URLs is typed by the user into the address bar) cannot callgetUserMedia().These kinds of URLs loaded from JavaScript code inherit the script's permissions.
• Any other situation in which there is no origin, such as when thesrcdoc attribute is used to specify the contents of a frame.

Examples

Using getUserMedia()

Generally, you will access theMediaDevices singleton object usingnavigator.mediaDevices, like this:

async function getMedia(constraints) {  let stream = null;  try {    stream = await navigator.mediaDevices.getUserMedia(constraints);    /* use the stream */  } catch (err) {    /* handle the error */  }}

Similarly, using the raw promises directly, the code looks like this:

navigator.mediaDevices  .getUserMedia(constraints)  .then((stream) => {    /* use the stream */  })  .catch((err) => {    /* handle the error */  });

Below are some examples of theconstraints parameter.

The following requests both audio and video without any specific requirements:

getUserMedia({  audio: true,  video: true,});

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:

getUserMedia({  audio: true,  video: { width: 1280, height: 720 },});

The browser will try to honor the constraints, and will return a matching track if supported by the underlying hardware.If not supported, the browser may attempt to crop and downscale a higher resolution stream from the underlying hardware in order to match the constraint (and might also reduce the frame rate if that was constrained).This behavior can be forced by setting theresizeMode constraint tocrop-and-scale (or disabled by setting it tonone):

getUserMedia({  audio: true,  video: { width: 1280, height: 720, resizeMode: "crop-and-scale" },});

The browser may return another resolution if an exact match is not available and the source is not to be scaled.

Torequire a capability and fail if it is not available, use the keywordsmin,max, orexact (a.k.a.min === max).The following demands a minimum resolution of 1280x720:

getUserMedia({  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 withOverconstrainedError, and the user will not be prompted.

The reason for the difference in behavior is that the keywordsmin,max, andexact are inherently mandatory — whereas plain values and a keyword calledideal are not.Here's a full example:

getUserMedia({  audio: true,  video: {    width: { min: 1024, ideal: 1280, max: 1920 },    height: { min: 576, ideal: 720, max: 1080 },  },});

Anideal 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 smallestfitness 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:

getUserMedia({  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:

getUserMedia({  audio: true,  video: { facingMode: "user" },});

Torequire the rear camera, use:

getUserMedia({  audio: true,  video: {    facingMode: { exact: "environment" },  },});

Another non-number constraint is thedeviceId constraint.If you have adeviceId frommediaDevices.enumerateDevices(), you can use it to request a specific device:

getUserMedia({  video: {    deviceId: myPreferredCameraDeviceId,  },});

The above will return the camera you requested, or a different camera if that specific camera is no longer available.Browsers' internally-available information, such as user preference, may also override your request.For example, when the user was asked for camera permissions, the camera they selected may take priority over the one you requested.Again, torequire the specific camera, you would use:

getUserMedia({  video: {    deviceId: {      exact: myExactCameraOrBustDeviceId,    },  },});

Width and height

This example gives a preference for camera resolution, and assigns the resultingMediaStream object to a video element.

// Prefer camera resolution nearest to 1280x720.const constraints = {  audio: true,  video: { width: 1280, height: 720 },};navigator.mediaDevices  .getUserMedia(constraints)  .then((mediaStream) => {    const video = document.querySelector("video");    video.srcObject = mediaStream;    video.onloadedmetadata = () => {      video.play();    };  })  .catch((err) => {    // always check for errors at the end.    console.error(`${err.name}: ${err.message}`);  });

Frame rate

Lower frame-rates may be desirable in some cases, like WebRTC transmissions with bandwidth restrictions.

const constraints = {  video: { frameRate: { ideal: 10, max: 15 } },};

Front and back camera

On mobile phones.

let front = false;document.getElementById("flip-button").onclick = () => {  front = !front;};const constraints = {  video: { facingMode: front ? "user" : "environment" },};

Specifications

Browser compatibility

See also

• The olderNavigator.getUserMedia() legacy API
• MediaDevices.enumerateDevices(): Listing available media devices
• WebRTC API
• Media Capture and Streams API
• Screen Capture API: Capturing screen contents as aMediaStream
• MediaDevices.getDisplayMedia(): Getting a stream containing screen contents
• Taking webcam photos: A tutorial on usinggetUserMedia() to take still photos rather than video