The url property of the RTCPeerConnectionIceErrorEvent interface is a string indicating the URL of the STUN or TURN server with which the error occurred.
A string.
This example creates a handler for icecandidateerror events, which creates human-readable messages describing the local network interface for the connection and the ICE server used to attempt the connection. It then calls a function to display those messages and the value of the event's errorText property.
pc.addEventListener("icecandidateerror", (event) => {
const networkInfo = `[Local interface: ${event.address}:${event.port}]`;
const iceServerInfo = `[ICE server: ${event.url}]`;
showMessage(event.errorText, iceServerInfo, networkInfo);
});