RTCPeerConnection.canTrickleIceCandidates

The read-only RTCPeerConnection property canTrickleIceCandidates returns a Boolean which indicates whether or not the remote peer can accept trickled ICE candidates.

ICE trickling is the process of continuing to send candidates after the initial offer or answer has already been sent to the other peer.

This property is only set after having called RTCPeerConnection.setRemoteDescription().  Ideally, your signaling protocol provides a way to detect trickling support, so that you don't need to rely on this property. A WebRTC browser will always support trickle ICE. If trickling isn't supported, or you aren't able to tell, you can check for a falsy value for this property and then wait until the value of iceGatheringState changes to "completed" before creating and sending the initial offer. That way, the offer contains all of the candidates.

Syntax

 var canTrickle = RTCPeerConnection.canTrickleIceCandidates;

Value

A Boolean that is true if the remote peer can accept trickled ICE candidates and false if it cannot. If no remote peer has been established, this value is null.

Note: This property's value is determined once the local peer has called RTCPeerConnection.setRemoteDescription(); the provided description is used by the ICE agent to determine whether or not the remote peer supports trickled ICE candidates.

Example

var pc = new RTCPeerConnection();
// The following code might be used to handle an offer from a peer when
// it isn't known whether it supports trickle ICE.
pc.setRemoteDescription(remoteOffer)
  .then(_ => pc.createAnswer())
  .then(answer => pc.setLocalDescription(answer))
  .then(_ =>     
    if (pc.canTrickleIceCandidates) {
      return pc.localDescription;
    }
    return new Promise(r => {
      pc.addEventListener('icegatheringstatechange', e => {
        if (e.target.iceGatheringState === 'complete') {
          r(pc.localDescription);
        }
      });
    });
  })
  .then(answer => sendAnswerToPeer(answer)) // signaling message
  .catch(e => handleError(e));

pc.addEventListener('icecandidate', e => {
  if (pc.canTrickleIceCandidates) {
    sendCandidateToPeer(e.candidate); // signaling message
  }
});

Specifications

Specification Status Comment
WebRTC 1.0: Real-time Communication Between Browsers
The definition of 'RTCPeerConnection.canTrickleIceCandidates' in that specification.
Candidate Recommendation Initial specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic support
Experimental
Chrome No support NoEdge Full support 15Firefox Full support 44IE ? Opera No support NoSafari ? WebView Android No support NoChrome Android No support NoEdge Mobile Full support YesFirefox Android Full support 44Opera Android No support NoSafari iOS ? Samsung Internet Android Full support 6.0

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

See also

Document Tags and Contributors

Contributors to this page: Sheppy, fscholz, fippo, jpmedley, abbycar, m_t, teoli
Last updated by: Sheppy,