webrtc-ip-leak

Tiny, zero-dependency browser utility to detect IP addresses (local and public) that the WebRTC stack can leak — even when a VPN or proxy is active. Runs entirely client-side; no data leaves the browser.

Why this exists

WebRTC gathers ICE candidates to establish peer connections, and that process can expose your real local IP and public IP to any web page via RTCPeerConnection — a classic privacy gap that bypasses many VPNs. This helper lets you detect it so you can warn users or test a VPN's WebRTC leak protection.

Install

npm install webrtc-ip-leak

Usage

import { detectWebRTCLeak } from "webrtc-ip-leak";
// or: const { detectWebRTCLeak } = require("webrtc-ip-leak");

const result = await detectWebRTCLeak({ timeout: 1500 });
console.log(result);
// {
//   supported: true,
//   ips:    ["192.168.1.20", "203.0.113.7"],
//   local:  ["192.168.1.20"],
//   public: ["203.0.113.7"]   // <-- if non-empty while on a VPN, you have a WebRTC leak
// }

If public contains your real ISP IP while connected to a VPN, your browser is leaking it through WebRTC.

API

detectWebRTCLeak(options?) → Promise<{ supported, ips, local, public }>

| option | default | description | |---|---|---| | timeout | 1500 | ms to gather ICE candidates | | iceServers | Google STUN | custom STUN/TURN servers |

• supported — whether the browser exposes RTCPeerConnection
• ips — all observed IPs
• local — RFC1918 / link-local / IPv6 ULA addresses
• public — routable addresses (the privacy-relevant ones)

How to fix a WebRTC leak

• Disable WebRTC in the browser, or use an extension that does.
• Use a VPN/browser that blocks WebRTC IP exposure.
• Run a full check (IP + DNS + WebRTC) — a hosted browser-based tester is available at AnonymFlow tools.

License

MIT