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.

Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

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.

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

This event is not cancelable and does not bubble.


Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("addstream", (event) => {});

onaddstream = (event) => {};

Event type

A MediaStreamEvent. Inherits from Event.

Event properties

A MediaStreamEvent being an Event, this event also implements these properties.

MediaStreamEvent.stream Read only

Contains the MediaStream containing the stream associated with the 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