WebRTC Leak: What It Is and How to Stop It in 2025

Introduction to WebRTC Leak

What is WebRTC?

• Real-time audio/video and data sharing
• End-to-end encryption
• Built-in support in all major browsers

WebRTC Peer-to-Peer Connection Diagram

How Does a WebRTC Leak Occur?

• When a WebRTC session is initiated, the browser exchanges network information, including IP addresses, with STUN/TURN servers.
• JavaScript running in the browser can access the WebRTC API and enumerate all available network interfaces, collecting both local and public IP addresses.
• This information can be exposed to websites, even if the user is connected via a VPN, because WebRTC requests bypass the VPN tunnel and reveal the real IP.

Example: JavaScript Code That Exposes WebRTC IP Addresses

1// WebRTC leak demo: Exposing IP addresses via JavaScript
2const getUserIPs = async () => {
3  const ips = [];
4  const pc = new RTCPeerConnection({
5    iceServers: []
6  });
7  pc.createDataChannel("");
8  pc.createOffer().then(sdp => pc.setLocalDescription(sdp));
9  pc.onicecandidate = event => {
10    if (event && event.candidate && event.candidate.candidate) {
11      const candidate = event.candidate.candidate;
12      const ipRegex = /([0-9]{1,3}(\.[0-9]{1,3}){3})/g;
13      const matches = candidate.match(ipRegex);
14      if (matches) {
15        matches.forEach(ip => {
16          if (!ips.includes(ip)) ips.push(ip);
17        });
18      }
19    }
20  };
21  // Wait a few seconds to gather candidates
22  await new Promise(resolve => setTimeout(resolve, 2000));
23  pc.close();
24  return ips;
25};
26getUserIPs().then(console.log);
27

Why WebRTC Leaks are a Privacy Concern

• Geolocation exposure, even when using a VPN
• Targeted surveillance or tracking
• Bypassing organizational privacy measures

How to Test for a WebRTC Leak

1. BrowserLeaks.com/WebRTC: Shows all IPs that can be discovered by WebRTC.
2. ipleak.net: Provides a comprehensive report, including WebRTC results.
3. ExpressVPN WebRTC Leak Test: Simple, focused tool for quick checks.

Step-by-Step Guide:

1. Connect to your VPN or proxy.
2. Open one of the above WebRTC leak test pages.
3. Compare the IP addresses shown under "WebRTC" with your real IP and VPN IP.
   • If your real IP is listed, your browser is leaking via WebRTC.
   • If only your VPN IP is shown, your setup is safe.

How to Fix or Prevent WebRTC Leaks

Chrome: Preventing WebRTC Leak with Extensions

• Install the WebRTC Network Limiter or uBlock Origin extension.
• Configure the extension to block WebRTC IP exposure.

1// In uBlock Origin, add this dynamic filtering rule:
2*webrtc-block
3

Firefox: Configuration Tweak to Block WebRTC Leak

1. Type about:config in the address bar.
2. Search for media.peerconnection.enabled.
3. Set the value to false.

Safari: Advanced Settings for WebRTC Leak Prevention

• Go to Preferences > Advanced > Experimental Features.
• Uncheck WebRTC mDNS ICE Candidates to prevent local IP exposure.
• Consider disabling WebRTC entirely if not needed.

Opera, Brave, Edge: Settings and Extensions

• In browser settings, search for "WebRTC" and disable features related to non-proxied UDP, if available.
• Use privacy extensions like WebRTC Control or uBlock Origin.

Tor Browser: Default Behavior

General Precautions and Best Practices

• Regularly update browsers and extensions.
• Test for WebRTC leaks after every browser or VPN update.
• Use privacy-focused browser builds or hardened configurations for sensitive use.
• Limit unnecessary permissions for installed extensions.
• Educate users and teams about the risks of WebRTC leaks.

WebRTC and VPNs: What You Need to Know

Ensuring Your VPN Protects Against WebRTC Leak

• Choose a VPN provider that specifically mentions WebRTC leak protection.
• Use browsers or extensions that block WebRTC leaks.
• Routinely test your VPN connection for leaks using the tools mentioned earlier.

Advanced: Disabling WebRTC via Code or Group Policy

Disabling WebRTC with JavaScript

1// Override WebRTC APIs to disable them in the browser environment
2if (window.RTCPeerConnection) {
3  window.RTCPeerConnection = undefined;
4}
5if (window.webkitRTCPeerConnection) {
6  window.webkitRTCPeerConnection = undefined;
7}
8

Disabling WebRTC via Group Policy (Windows)

• Use Group Policy Editor to set Chrome or Edge policies:
  • Go to Computer Configuration > Administrative Templates > Google > Google Chrome > WebRTC
  • Set WebRTC IP Handling Policy to DisableNonProxiedUdp.

Conclusion