Glossary · Networking
WebRTC leak
When a browser's real-time communication feature exposes your true IP address even though your traffic runs through a proxy.
WebRTC is the browser technology behind video calls and peer-to-peer connections in the page, and to make those direct connections work it needs to know your real address. That legitimate need is the problem: a script can ask the browser for the addresses WebRTC has discovered and read your true IP straight past the proxy.
It is insidious precisely because it operates at the browser layer, not the network layer. Your proxy is doing its job at the connection level while the browser volunteers your real address through a side channel the proxy never sees.
Defences are client-side: disable or restrict WebRTC, or use a browser configured not to expose local addresses. As with DNS, the only way to know you are safe is to test from behind the proxy and look for your real address, rather than assume the exit IP is the whole picture.
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