WebRTC leak test
WebRTC is the protocol behind video calls in your browser. To work, it can ask a STUN server for your public IP — even when you're connected to a VPN. Here's what your browser exposes right now.
Why does this happen?
Browsers needed a way for two random people to start a video call without a server in between. The protocol they came up with — WebRTC — works by asking a STUN server, "What's my public IP, and what port am I reachable on?" Helpful for video calls. Less helpful when any random website can ask the same question.
On most modern setups your VPN's adapter is the one that answers, and the IP returned is the VPN's. But if your operating system has multiple network interfaces (which it probably does), it may answer from your ISP's adapter instead — and that's the leak.
How to plug it
PlanetProxy's desktop and mobile apps install a system-level WebRTC mediator that forces all candidate gathering through the VPN's interface. No browser extension needed.
If you're not running PlanetProxy, the alternatives are: install uBlock Origin and flip on "Prevent WebRTC from leaking local IP", switch your browser to one that respects the privacy.network.peerConnectionEnabled flag (Firefox), or just disable WebRTC entirely and accept that some video chat sites will stop working.