The RTCPeerConnection.onicegatheringstatechange property is an event handler which specifies a function to be called when the icegatheringstatechange event is sent to an RTCPeerConnection instance. This happens when the ICE gathering state—that is, whether or not the ICE agent is actively gathering candidates—changes.

You don't need to watch for this event unless you have specific reasons to want to closely monitor the state of ICE gathering.


RTCPeerConnection.onicegatheringstatechange = eventHandler;


A function you provide which is passed a single parameter: an Event object containing the icegatheringstatechange event. You can determine the new state of ICE gathering by looking at the value of the RTCPeerConnection.iceGatheringState property.


This example updates status information presented to the user to let them know what's happening by examining the current value of the iceGatheringState property each time it changes and changing the contents of a status display based on the new information.

The status is presented as text in a <div> element:

<div id="iceStatus"></div>

The actual event handler looks like this:

pc.onicegatheringstatechange = function() {
  let label = "Unknown";

  switch(pc.iceGatheringState) {
    case "new":
    case "complete":
      label = "Idle";
    case "gathering":
      label = "Determining route";

  document.getElementById("iceStatus").innerHTML = label;


WebRTC 1.0: Real-Time Communication Between Browsers (WebRTC 1.0)
# dom-rtcpeerconnection-onicegatheringstatechange

Browser compatibility

BCD tables only load in the browser

See also