RTCPeerConnection: addstream event

Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The obsolete addstream event is sent to an RTCPeerConnection when new media, in the form of a MediaStream object, has been added to it.

Warning: This event has been removed from the WebRTC specification. You should instead watch for the track event, which is sent for each media track added to the RTCPeerConnection.

Bubbles No
Cancelable No
Interface MediaStreamEvent
Event handler property RTCPeerconnection.onaddstream

You can, similarly, watch for streams to be removed from the connection by monitoring the removestream event.


This example looks to determine if the user's browser supports the track event. If it does, a track event listener is set up; otherwise, an addstream event listener is set up. pc is an RTCPeerConnection.

if (pc.addTrack !== undefined) {
  pc.ontrack = ev => {
    ev.streams.forEach(stream => doAddStream(stream));
} else {
  pc.onaddstream = ev => {

This calls a function doAddStream() once for each stream being added to the RTCPeerConnection, regardless of whether the browser sends addstream or track.

You can also use the addEventListener() method to set an event listener:

pc.addEventListener("addstream", ev => doAddStream(ev.stream), false);

Browser compatibility

BCD tables only load in the browser

See also