GLOSSARY · WEB REAL-TIME COMMUNICATION
WebRTC
WebRTC is a set of browser features that lets web pages make direct audio, video and data connections between devices, without plug-ins. Video calls in the browser, screen sharing and some file transfer tools rely on it.
Why it matters
To set up a direct connection, WebRTC gathers the addresses your device can be reached at, including local and sometimes public ones, and shares them with the other side. A page can request this list without a call taking place, which means WebRTC can expose your real address even when a VPN or proxy is in use. Browsers have reduced this, but behaviour varies.
In practice
Run the WebRTC leak test with your VPN on and see whether an address other than the VPN's appears. Fixes include browser settings or extensions that limit the addresses WebRTC reveals, and using a VPN app that blocks WebRTC leaks. Disabling WebRTC entirely can break video calls, so test the sites you use afterwards.
Related terms
- STUN: STUN is a simple protocol where a device asks a public server, "what address and port do you see me coming from?" The server replies with the answer.
- Public vs. private IP address: A public IP address is reachable across the internet and is the one websites see.
- VPN: A VPN creates an encrypted tunnel between your device and a server operated by the VPN service.
- DNS leak: A DNS leak is when your device sends its DNS lookups to a resolver you did not intend, usually your internet provider's, while you believe a VPN or proxy is handling your traffic.