MediaStream.onaddtrack

The MediaStream.onaddtrack property is an EventHandler which specifies a function to be called when the addtrack event occurs on a MediaStream instance. This happens when a new track of any kind is added to the media stream. This event is fired when the browser adds a track to the stream (such as when a RTCPeerConnection is renegotiated or a stream being captured using HTMLMediaElement.captureStream() gets a new set of tracks because the media element being captured loaded a new source.

The addtrack event does not get fired when JavaScript code explicitly adds tracks to the stream (by calling addTrack()).

Syntax

MediaStream.onaddtrack = eventHandler;

Value

This should be set to a function which you provide that accepts as input a MediaStreamTrackEvent object representing the addtrack event which has occurred. The MediaStreamTrack representing the track which was added is specified in the event's track property.

Example

This example adds a listener which, when a new track is added to the stream, appends a new item to a list of tracks; the new item shows the track's kind ("audio" or "video") and label.

stream.onaddtrack = function(event) {
  let trackList = document.getElementById("tracks");
  let label = document.createElement("li");

  label.innerHTML = event.track.kind + ": " + event.track.label;
  trackList.appendChild(label);
};

Specifications

Specification Status Comment
Media Capture and Streams
The definition of 'MediaStream.onaddtrack' in that specification.
Candidate Recommendation Initial specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support YesEdge Full support 12Firefox Full support 50IE ? Opera ? Safari ? WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 50Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Contributors to this page: fscholz, Sheppy
Last updated by: fscholz,