The id property of the RTCStats dictionary is a string which uniquely identifies the object for which this RTCStats object provides statistics.

Using the id, you can correlate two or more RTCStats-based objects in order to monitor statistics over time for a given WebRTC object, such as an RTP stream, an RTCPeerConnection, or an RTCDataChannel.

A string which uniquely identifies the object for which this RTCStats-based object provides statistics.

The format of the ID string is not defined by the specification, so you cannot reliably make any assumptions about the contents of the string, or assume that the format of the string will remain unchanged for a given object type.