WebRTC (Web Real-Time Communication) is a powerful browser API that enables peer-to-peer connections for video calls, file sharing, and data channels. However, it has a significant privacy flaw: it exposes your real IP address even when you're using a VPN or proxy.

The problem occurs because WebRTC uses STUN servers to discover the optimal path between peers. During this ICE (Interactive Connectivity Establishment) negotiation process, the browser queries multiple network interfaces and reports all discovered IP addresses — including your local IP and your actual public IP.

For multi-account users, this creates serious risks. If you're managing separate browser profiles for different accounts, WebRTC can leak your underlying IP and reveal that multiple "different" identities share the same physical machine. E-commerce platforms, social networks, and ad networks actively use this to detect account farms.

Testing for WebRTC leaks requires checking what IP addresses your browser exposes. Tools like BrowserLeaks.com's WebRTC test or the WebRTC IP Leak test at ipleak.net can show you exactly what's being disclosed. If your VPN's IP doesn't match what WebRTC reports, you have a leak.

To properly isolate WebRTC for multi-account setups, you need browser-level isolation — not just VPN-level. Tools like FireKey (https://usefirekey.com) handle this by creating isolated browser environments with separate WebRTC configurations, preventing cross-account IP correlation. This is essential for anyone managing multiple accounts on platforms that use fingerprinting for fraud detection.