MediaTrackConstraints.deviceId

The MediaTrackConstraints dictionary's deviceId property is a ConstrainDOMString describing the requested or mandatory constraints placed upon the value of the deviceId constrainable property.

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

Syntax

var constraintsObject = { deviceId: constraint };

constraintsObject.deviceId = constraint;

Value

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

Device IDs are unique for a given origin, and are guaranteed to be the same 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 deviceId when you call getCapabilities().

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

Example

See "Example: Constraint exerciser" in Capabilities, constraints, and settings for an example.

Specifications

Specification	Status	Comment
Media Capture and Streams The definition of 'deviceId' in that specification.	Editor's Draft	Initial specification.

Browser compatibility

See also

• Media Capture and Streams API
• Capabilities, constraints, and settings
• MediaTrackConstraints
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaStreamTrack