← Back to guides
January 24, 2025 • 5 mins read •
#vpn #kill-switch #dns-leak

VPN Kill Switch, DNS & WebRTC Leaks Explained

Learn about VPN kill switches, DNS leaks, and WebRTC leaks. Understand how to prevent IP address exposure and protect your privacy.

VPN Kill Switch, DNS & WebRTC Leaks Explained

Summary

A kill switch disconnects your internet if the VPN fails, preventing IP leaks. DNS leaks occur when DNS queries bypass the VPN. WebRTC leaks happen when browsers reveal your real IP. All three can expose your real IP address, defeating VPN protection.

Why VPN Leaks Matter

If your VPN leaks your real IP address: - Your location can be tracked - Your ISP can see your activity - Websites can identify you - Your VPN protection is compromised

Understanding Kill Switches

What is a Kill Switch?

A kill switch automatically disconnects your internet connection if the VPN connection drops, preventing your real IP from being exposed.

How It Works

  1. VPN monitors connection status
  2. If VPN disconnects, kill switch activates
  3. Internet connection is blocked
  4. Your real IP stays hidden
  5. Reconnect VPN to restore internet

Types of Kill Switches

Application-Level Kill Switch: - Blocks specific apps if VPN drops - More granular control - Some apps may still work

System-Level Kill Switch: - Blocks all internet if VPN drops - Maximum protection - Internet completely disabled until VPN reconnects

Why You Need One

Without a kill switch: - VPN disconnects silently - Your real IP is exposed - You may not notice the leak - Your privacy is compromised

Understanding DNS Leaks

What is a DNS Leak?

A DNS leak occurs when your DNS queries (website lookups) go through your ISP instead of your VPN, revealing what websites you visit.

How DNS Works

  1. You type a website address
  2. Your device asks DNS server for IP address
  3. DNS server responds with IP
  4. You connect to website

With VPN: DNS queries go through VPN’s DNS servers With Leak: DNS queries go through your ISP’s DNS servers

Why DNS Leaks Happen

  • VPN doesn’t properly route DNS
  • Operating system uses default DNS
  • Browser uses hardcoded DNS
  • VPN configuration issues

How to Test for DNS Leaks

  1. Connect to VPN
  2. Visit dnsleaktest.com
  3. Run extended test
  4. Check if results show your ISP’s DNS
  5. If yes, you have a DNS leak

How to Prevent DNS Leaks

  • Use VPNs with DNS leak protection
  • Configure custom DNS in VPN settings
  • Use VPN’s DNS servers only
  • Test regularly for leaks

Understanding WebRTC Leaks

What is WebRTC?

WebRTC (Web Real-Time Communication) is a browser technology for voice, video, and data sharing. It can reveal your real IP address even when using a VPN.

How WebRTC Leaks Work

  1. Browser uses WebRTC for communication
  2. WebRTC discovers local IP addresses
  3. These IPs can be accessed by websites
  4. Your real IP is exposed
  5. VPN protection is bypassed

Why WebRTC Leaks Happen

  • WebRTC is enabled by default in browsers
  • Browsers discover local network IPs
  • Websites can access these IPs via JavaScript
  • VPN doesn’t block WebRTC requests

How to Test for WebRTC Leaks

  1. Connect to VPN
  2. Visit browserleaks.com/webrtc
  3. Check if real IP is visible
  4. If yes, you have a WebRTC leak

How to Prevent WebRTC Leaks

Browser Extensions: - uBlock Origin (blocks WebRTC) - WebRTC Leak Prevent (Chrome/Edge) - Disable WebRTC (Firefox)

Browser Settings: - Firefox: about:config → media.peerconnection.enabled = false - Chrome: Use extension (no native setting) - Brave: WebRTC blocking built-in

VPN Features: - Some VPNs block WebRTC - Check VPN documentation - Use VPNs with WebRTC protection

VPNs with Best Leak Protection

Mullvad

  • Kill switch: ✅ Yes
  • DNS leak protection: ✅ Yes
  • WebRTC protection: ⚠️ Browser-dependent

IVPN

  • Kill switch: ✅ Yes (always-on option)
  • DNS leak protection: ✅ Yes
  • WebRTC protection: ⚠️ Browser-dependent

Proton VPN

  • Kill switch: ✅ Yes
  • DNS leak protection: ✅ Yes
  • WebRTC protection: ⚠️ Browser-dependent

Best Practices

For Kill Switches:

  1. Always enable kill switch
  2. Use system-level if available
  3. Test kill switch functionality
  4. Keep VPN app updated
  5. Monitor connection status

For DNS Leaks:

  1. Use VPN’s DNS servers
  2. Test for leaks regularly
  3. Configure DNS in VPN settings
  4. Avoid custom DNS unless necessary
  5. Use VPNs with leak protection

For WebRTC Leaks:

  1. Disable WebRTC in browser
  2. Use browser extensions
  3. Test for leaks regularly
  4. Use browsers with WebRTC blocking
  5. Consider VPNs that block WebRTC

Testing Your VPN

Complete Leak Test:

  1. Connect to VPN
  2. Check IP: Visit ipleak.net
  3. Check DNS: Visit dnsleaktest.com
  4. Check WebRTC: Visit browserleaks.com/webrtc
  5. Test Kill Switch: Disconnect VPN manually, check if internet stops

What to Look For:

  • IP address matches VPN server location
  • DNS servers belong to VPN provider
  • No WebRTC leaks showing real IP
  • Kill switch activates on disconnect

Common Issues and Fixes

Kill Switch Not Working

  • Update VPN app
  • Check firewall settings
  • Reinstall VPN
  • Contact VPN support

DNS Leaks

  • Configure DNS in VPN settings
  • Use VPN’s DNS servers
  • Disable custom DNS
  • Test and verify

WebRTC Leaks

  • Install browser extension
  • Disable WebRTC in browser
  • Use privacy-focused browser
  • Test regularly

Conclusion

Kill switches, DNS leaks, and WebRTC leaks are critical for VPN security. A VPN is only effective if it actually protects your IP address. Always enable kill switches, test for DNS and WebRTC leaks, and use VPNs with built-in leak protection.

Choose VPNs that offer kill switches and DNS leak protection, and configure your browser to prevent WebRTC leaks. Regular testing ensures your VPN is actually protecting your privacy.

Remember: A VPN that leaks your IP is worse than no VPN at all—it gives a false sense of security. Test your setup regularly and fix any leaks immediately.