What the test does
When you press Run, your browser creates a WebRTC connection offer and asks two public STUN servers (Google and Cloudflare) which address they see. Nothing is sent to anyone else, and the results stay in this page.
Host candidates are your device's own addresses; modern browsers hide the private ones behind a random name ending in .local. Server-reflexive (srflx) candidates are your public address as the STUN server saw it.
Is it a leak?
Compare the public addresses with the address this site sees. If you use a VPN and WebRTC shows your provider's address instead of the VPN's, WebRTC is going around the tunnel: switch on your VPN's leak protection, or limit WebRTC in your browser (Firefox: media.peerconnection.enabled; Chrome and Edge: an extension such as WebRTC Network Limiter).
Questions
- My public address appears. Is that a leak?
- Only if it differs from the address websites already see. Without a VPN, WebRTC showing your public address reveals nothing new.
- Why are there no candidates?
- WebRTC is disabled, a privacy extension blocks it, or a firewall blocks UDP so the STUN servers cannot answer.