groupId property is a browsing-session unique
string which identifies the group of devices which includes the source
MediaStreamTrack. This lets you determine what value was selected
to comply with your specified constraints for this property's value as described in the
MediaTrackConstraints.groupId property you provided when calling either
If needed, you can determine whether or not this constraint is supported by checking
the value of
MediaTrackSupportedConstraints.groupId as returned by a call
MediaDevices.getSupportedConstraints(). However, typically this is
unnecessary since browsers will ignore any constraints they're unfamiliar with.
A string whose value is a browsing-session unique identifier for a group of devices which includes the source of the track's contents. Two devices share the same group ID if they belong to the same physical hardware device. For example, a headset has two devices on it: a microphone which can serve as a source for audio tracks and a speaker which can serve as an output for audio.
The group ID is not usable across multiple browsing sessions. However, it can be used to ensure that audio input and output are both being performed on the same headset, for example, or to ensure that the built-in camera and microphone on a phone are being used for video conferencing purposes.
The actual value of the string, however, is determined by the source of the track, and there is no guarantee what form it will take, although the specification does recommend it be a GUID.
Since this property isn't stable across browsing sessions, its usefulness when calling
getUserMedia() is generally limited to
ensuring that tasks performed during the same browsing session use devices from the same
group (or that they don't use devices from the same group). There is no situation in
which the groupId is useful when calling
applyConstraints(), since the
value can't be changed.
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