WebRTC is the set of APIs that lets two browsers exchange audio, video and data directly, without a central server.
The three components
Signalling: outside WebRTC, handled by your application, lets both sides agree on codecs and exchange candidates. ICE: the mechanism that discovers possible paths between peers. STUN and TURN: the first discovers the public address seen from outside; the second relays traffic when a direct connection is impossible.
Why it needs your IP
To connect two devices directly, each side must know where the other is. STUN reports the public address observed by the internet — the same principle as your IP lookup.
The privacy dilemma
The candidate list generated by ICE includes internal and external addresses. That is great for fast connections and is exactly what allows a real address to be detected behind a VPN.
Where it shows up
Browser video calls, screen sharing, multiplayer games and peer-to-peer file transfer. The Browser Checker shows whether your browser supports WebRTC and other modern APIs.