Browsers have WebRTC for real - time video / audio.To make P2P connections work, it needs to know your < em > real physical IP address, bypassing proxies.

1. The STUN Server Trick

WebRTC sends a UDP packet to a STUN server asking: "What is my public IP?" This happens inside the browser engine, often ignoring the VPN tunnel.

Fix: Disable WebRTC in your browser config (media.peerconnection.enabled = false in Firefox).