Web/API/RTCTrackEvent

The WebRTC API interface RTCTrackEvent represents the track event, which is sent when a new MediaStreamTrack is added to an RTCRtpReceiver which is part of the RTCPeerConnection. The target is the RTCPeerConnection object to which the track is being added.

This event is sent by the WebRTC layer to the web site or application, so you will not typically need to instantiate an RTCTrackEvent yourself.

Constructor

RTCTrackEvent(): Creates and returns a new RTCTrackEvent object, initialized with properties taken from the specified RTCTrackEventInit dictionary. You will probably not need to create new track events yourself, since they're typically created by the WebRTC infrastructure and sent to the connection's ontrack event handler.

Properties

Since RTCTrackEvent is based on Event, its properties are also available.

receiver Read only: The RTCRtpReceiver used by the track that's been added to the RTCPeerConnection.
streams Read only Optional: An array of MediaStream objects, each representing one of the media streams to which the added track belongs. By default, the array is empty, indicating a streamless track.
track Read only: The MediaStreamTrack which has been added to the connection.
transceiver Read only: The RTCRtpTransceiver being used by the new track.

Track event types

There is only one type of track event.

`track`

The track event is sent to the RTCPeerConnection when a new track has been added to the connection. By the time the track event is delivered to the RTCPeerConnection's ontrack handler, the new media has completed its negotiation for a specific RTCRtpReceiver (which is specified by the event's receiver property).

In addition, the MediaStreamTrack specified by the receiver's track is the same one specified by the event's track, and the track has been added to any associated remote MediaStream objects.

You can add a track event listener to be notified when the new track is available so that you can, for example, attach its media to a <video> element, using either RTCPeerConnection.addEventListener() or the ontrack event handler property.

Note: It may be helpful to keep in mind that you receive the track event when a new inbound track has been added to your connection, and you call addTrack() to add a track to the far end of the connection, thereby triggering a track event on the remote peer.

Example

This simple example creates an event listener for the track event which sets the srcObject of the <video> element with the ID videobox to the first stream in the list passed in the event's streams array.

peerConnection.addEventListener("track", e => {
  let videoElement = document.getElementById("videobox");
  videoElement.srcObject = e.streams[0];
}, false);

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between BrowsersThe definition of 'RTCTrackEvent' in that specification.	Candidate Recommendation	Initial specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`RTCTrackEvent`	Chrome Full support 56	Edge Full support ≤18	Firefox Full support 22	IE No support No	Opera Full support 43	Safari Full support Yes	WebView Android Full support 56	Chrome Android Full support 56	Firefox Android Full support 44	Opera Android Full support 43	Safari iOS Full support Yes	Samsung Internet Android Full support 6.0
`receiver`	Chrome Full support 56	Edge Full support ≤18	Firefox Full support 22	IE No support No	Opera Full support 43	Safari Full support Yes	WebView Android Full support 56	Chrome Android Full support 56	Firefox Android Full support 44	Opera Android Full support 43	Safari iOS Full support Yes	Samsung Internet Android Full support 6.0
`streams`	Chrome Full support 56	Edge Full support ≤18	Firefox Full support 22	IE No support No	Opera Full support 43	Safari Full support Yes	WebView Android Full support 56	Chrome Android Full support 56	Firefox Android Full support 44	Opera Android Full support 43	Safari iOS Full support Yes	Samsung Internet Android Full support 6.0
`track`	Chrome Full support 56	Edge Full support ≤18	Firefox Full support 22	IE No support No	Opera Full support 43	Safari Full support Yes	WebView Android Full support 56	Chrome Android Full support 56	Firefox Android Full support 44	Opera Android Full support 43	Safari iOS Full support Yes	Samsung Internet Android Full support 6.0
`transceiver`	Chrome Full support 69	Edge Full support ≤18	Firefox Full support 59	IE No support No	Opera Full support 43	Safari Full support Yes	WebView Android Full support 69	Chrome Android Full support 69	Firefox Android Full support 59	Opera Android Full support 43	Safari iOS Full support Yes	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
No support: No support

RTCTrackEvent by Mozilla Contributors is licensed under CC-BY-SA 2.5.