WebRTC Leak Test

How the WebRTC leak test works

Click Start leak test. The tool opens anRTCPeerConnection configured with public STUN servers (Google and Cloudflare). The browser gathers ICE candidates — potential paths a peer connection could take — and each candidate includes an IP address.

Host candidates reveal your LAN-side IP. Server-reflexive (srflx) candidates — learned from the STUN server's response — reveal the public IP your connection actually uses. Both are shown above, classified as local or public.

Why this matters for VPN users: if you are connected to a VPN but a public IP shown here is your real ISP IP (not the VPN endpoint), your network location is leaking through WebRTC even while your web browsing appears routed.

Why recent browsers show .local addresses: modern Chrome, Firefox, and Safari obscure LAN-side IPs behind mDNS host names by default — that is the expected and correct behaviour.

No addresses are sent to CheckMySys. The tool only contacts public STUN servers to elicit the server-reflexive candidate; the browser then hands it to this JavaScript where it is classified and shown.