The onsignalingstatechange event handler property of the RTCPeerConnection interface specifies a function to be called when the signalingstatechange event occurs on an RTCPeerConnection interface. The function receives as input the event object of type Event; this event is sent when the peer connection's signalingState changes, which may happen either because of a call to setLocalDescription() or to setRemoteDescription().


rtcPeerConnection.onsignalingstatechange = errorHandler;


Set this to a function which you provide that receives an Event object as input; this contains the signalingstatechange event. This event object doesn't provide details about what changed, but you can examine the signalingState property to determine what the new state is.

You may also, as always, set up a handler for the signalingstatechange event using addEventListener():

myRTCPeerConnection.addEventListener("signalingstatechange", mySignalingStateChangeHandler);

Or, using an anonymous (inline) handler:

myRTCPeerConnection.addEventListener("signalingstatechange", event => {
  /* handle the event here */


This snippet shows a handler for signalingstatechange that looks for the "have-local-pranswer" signaling stateā€”indicating that a remote offer has been received and a local description of type "pranswer" has been applied in response.

pc.onsignalingstatechange = function(event) {
  if (pc.signalingState === "have-local-pranswer") {
    // setLocalDescription() has been called with an answer


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
onsignalingstatechangeChrome Full support 28Edge Full support 15Firefox Full support 22IE No support NoOpera Full support 43
Full support 43
Notes Promise-based version.
No support 37Ā ā€” 43
Safari Full support 11WebView Android Full support YesChrome Android Full support 28Firefox Android Full support 44Opera Android Full support 43
Full support 43
Notes Promise-based version.
No support 37Ā ā€” 43
Safari iOS Full support YesSamsung Internet Android Full support 6.0


Full support Ā 
Full support
No support Ā 
No support
See implementation notes.
See implementation notes.

See also