Windows IP Leak Test

Windows 10 and Windows 11 have several built-in features that can cause IP leaks even when using a VPN. These operating system-specific vulnerabilities — including Teredo tunneling, Smart Multi-Homed Name Resolution, and IPv6 preferences — can expose your real IP address, location, and ISP despite being connected to a VPN. This guide shows you exactly how to test for IP leaks on Windows and fix Windows-specific leak causes.

Why Windows Leaks More Than Other Operating Systems

Windows has a reputation for being more prone to VPN leaks than macOS or Linux. This isn't because Windows is inherently insecure, but because Microsoft prioritizes connectivity and user convenience over privacy.

Windows-Specific Leak Causes

1. Teredo Tunneling

Teredo is a Microsoft technology designed to help IPv6 traffic traverse IPv4 networks. The problem: Teredo can bypass your VPN entirely, sending IPv6 traffic directly to the internet and exposing your real IP address.

Analogy: Imagine you're sending all your mail through a secure PO Box (your VPN). Teredo is like a backdoor mail slot in your house that some letters accidentally go through, bypassing the PO Box entirely.

2. Smart Multi-Homed Name Resolution (SMHNR)

Introduced in Windows 8, SMHNR sends DNS queries to all available network interfaces simultaneously (your VPN and your regular internet connection) and uses whichever responds first. This means:

• DNS queries leak to your ISP even when using a VPN
• Your ISP can see which websites you're visiting
• Your VPN's DNS protection is bypassed

3. IPv6 Preference

Windows prefers IPv6 connections over IPv4 when available. If your VPN only routes IPv4 traffic (common with older VPN services), all IPv6 traffic bypasses the VPN, leaking your real IP address.

4. Network Location Awareness

Windows automatically detects network changes and adjusts settings accordingly. During VPN connection transitions, this service can briefly expose your real IP before the VPN tunnel fully establishes.

5. Windows Update

Windows Update traffic can sometimes bypass VPN connections, especially if your VPN uses split tunneling or if Windows routes update traffic through a "trusted" interface.

How to Test for IP Leaks on Windows

Testing for IP leaks on Windows is straightforward but requires following the correct process:

Step 1: Check Your Real IP Address (Baseline Test)

1. Disconnect from your VPN (if currently connected)
2. Open your web browser (Edge, Chrome, Firefox, etc.)
3. Visit dovpn.com/ip-leak-test
4. Record the following information:
   • Your IPv4 address
   • Your IPv6 address (if shown)
   • Your ISP name
   • Your detected location (city/region)

Example: If you're in New York using Verizon, you might see:

• IPv4: 108.27.145.82
• IPv6: 2600:1700:1234:5678::1
• ISP: Verizon
• Location: New York, NY, USA

Step 2: Connect to Your VPN

1. Open your VPN application (NordVPN, Surfshark, ExpressVPN, etc.)
2. Choose a server in a different country (e.g., if you're in the US, connect to UK, Germany, or Netherlands)
3. Wait for the VPN connection to fully establish (look for "Connected" status)
4. Verify in your VPN app that you're connected

Step 3: Run the IP Leak Test

1. With your VPN still connected, visit dovpn.com/ip-leak-test
2. The tool will automatically check for:
   • IPv4 leaks: Is your real IPv4 address visible?
   • IPv6 leaks: Is your real IPv6 address leaking?
   • DNS leaks: Are DNS queries going to your ISP?
   • WebRTC leaks: Is your browser exposing your local IP?
3. Review the results carefully

Step 4: Interpret Your Results

✅ No Leaks Detected (Your VPN is Working):

• The displayed IP address is in the country you selected (e.g., if you connected to Germany, you see a German IP)
• The ISP shown is your VPN provider (not Verizon, Comcast, AT&T, etc.)
• No IPv6 address is displayed (or it shows your VPN's IPv6)
• DNS servers belong to your VPN provider
• No local IP addresses are exposed via WebRTC

❌ IP Leak Detected (Your VPN is Leaking):

• Your real IPv4 or IPv6 address is visible
• Your actual ISP (Verizon, Comcast, etc.) is shown
• Your true location (New York) is displayed instead of VPN location (Germany)
• DNS servers belong to your ISP instead of your VPN
• Multiple IP addresses appear (mixing real + VPN IPs)

Common Windows-Specific Leak Causes

If you detected a leak, here are the most common causes specific to Windows:

1. IPv6 Not Disabled

Problem: Your VPN routes IPv4 traffic but ignores IPv6, and Windows prefers IPv6 connections.

Result: All IPv6 traffic bypasses your VPN, leaking your real IP address.

Fix: Disable IPv6 entirely (see below).

2. Teredo Tunneling Enabled

Problem: Teredo creates an IPv6 tunnel over IPv4, bypassing your VPN.

Result: IPv6 leaks and potential IPv4 exposure.

Fix: Disable Teredo (see below).

3. Smart Multi-Homed Name Resolution (DNS Leaks)

Problem: Windows sends DNS queries to all network interfaces, including your unprotected ISP connection.

Result: Your ISP can see which websites you visit.

Fix: Disable SMHNR via registry edit (see below).

4. VPN Kill Switch Not Enabled

Problem: Your VPN connection drops momentarily, but Windows continues routing traffic through your regular connection.

Result: Temporary IP leaks during reconnection.

Fix: Enable your VPN's kill switch feature.

5. WebRTC in Browser

Problem: Your browser (Edge, Chrome, Firefox) uses WebRTC to establish peer-to-peer connections, which can expose your local IP.

Result: Local IP address visible to websites.

Fix: Disable WebRTC or install blocking extensions (see below).

Fix #1: Disable IPv6 on Windows

This is the most important fix for Windows VPN leaks. If your VPN doesn't fully support IPv6, disabling it prevents all IPv6 leak vulnerabilities.

Method 1: Disable IPv6 via Network Settings (Easy)

1. Press Windows Key + R to open Run dialog
2. Type ncpa.cpl and press Enter
3. Right-click your active network connection (usually "Ethernet" or "Wi-Fi")
4. Click Properties
5. Scroll down and uncheck "Internet Protocol Version 6 (TCP/IPv6)"
6. Click OK
7. Restart your computer
8. Reconnect to your VPN and test again

Method 2: Disable IPv6 via Command Prompt (Advanced)

For a system-wide IPv6 disable:

1. Press Windows Key + X and select "Terminal (Admin)" or "Command Prompt (Admin)"
2. Run the following command:

netsh interface ipv6 set privacy state=disabled
netsh interface ipv6 set global randomizeidentifiers=disabled
netsh interface ipv6 set teredo disabled

3. Restart your computer
4. Verify IPv6 is disabled by running: ipconfig (you should see no IPv6 addresses)

Fix #2: Disable Teredo Tunneling

Teredo is a major source of IPv6 leaks on Windows. Disabling it is essential:

1. Press Windows Key + X and select "Terminal (Admin)" or "Command Prompt (Admin)"
2. Run this command:

netsh interface teredo set state disabled

3. Verify Teredo is disabled:

netsh interface teredo show state

You should see: State: disabled

4. Restart your computer
5. Reconnect to your VPN and test for leaks

Fix #3: Fix DNS Leaks on Windows

Windows' Smart Multi-Homed Name Resolution causes DNS leaks. Here's how to fix it:

Method 1: Enable VPN DNS Settings

1. Check your VPN app settings for "DNS Leak Protection" or "Use VPN DNS"
2. Enable this feature (should be on by default with quality VPNs)
3. Reconnect to your VPN
4. Test for DNS leaks

Method 2: Disable Smart Multi-Homed Name Resolution (Registry Edit)

⚠️ Warning: Editing the Windows Registry can cause system issues if done incorrectly. Back up your registry before proceeding.

1. Press Windows Key + R and type regedit, then press Enter
2. Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters
3. Right-click in the right pane → New → DWORD (32-bit) Value
4. Name it: DisableSmartNameResolution
5. Double-click it and set Value to: 1
6. Click OK
7. Restart your computer

Method 3: Set Manual DNS Servers

1. Press Windows Key + R, type ncpa.cpl, press Enter
2. Right-click your active network connection → Properties
3. Select "Internet Protocol Version 4 (TCP/IPv4)" → Properties
4. Select "Use the following DNS server addresses"
5. Enter your VPN's DNS servers (check your VPN provider's documentation) or use privacy-focused DNS:
   • Cloudflare: 1.1.1.1 and 1.0.0.1
   • Quad9: 9.9.9.9 and 149.112.112.112
6. Click OK → OK
7. Flush DNS cache: Open Command Prompt and run ipconfig /flushdns
8. Reconnect to your VPN and test

Fix #4: Block WebRTC Leaks

WebRTC leaks happen at the browser level. Fix them based on your browser:

Microsoft Edge

1. Install the WebRTC Leak Prevent extension from Edge Add-ons
2. Enable the extension
3. Restart Edge
4. Test for WebRTC leaks

Google Chrome

1. Install WebRTC Leak Prevent from Chrome Web Store
2. Enable the extension
3. Restart Chrome
4. Test for WebRTC leaks

Firefox

1. Type about:config in the address bar and press Enter
2. Click "Accept the Risk and Continue"
3. Search for: media.peerconnection.enabled
4. Toggle it to false (double-click)
5. Restart Firefox
6. Test for WebRTC leaks

Advanced Windows Leak Fixes

Disable Network Location Awareness

1. Press Windows Key + R, type services.msc, press Enter
2. Find "Network Location Awareness"
3. Right-click → Properties
4. Set Startup type to: Disabled
5. Click Stop → Apply → OK
6. Restart your computer

Configure Windows Firewall for VPN

1. Open Settings → Privacy & Security → Windows Security → Firewall & network protection
2. Click "Allow an app through firewall"
3. Click "Change settings" (requires admin)
4. Find your VPN app in the list
5. Ensure it's checked for both Private and Public networks
6. Click OK

Enable VPN Kill Switch

Most quality VPN apps include a kill switch (sometimes called "Network Lock"):

1. Open your VPN app settings
2. Look for "Kill Switch," "Network Lock," or "Internet Kill Switch"
3. Enable it
4. Reconnect to your VPN

What it does: If your VPN connection drops, the kill switch blocks all internet traffic, preventing IP leaks during reconnection.

Use Trusted VPN Protocols

In your VPN app, choose the most secure protocol:

1. Best choice: WireGuard (fast, modern, built-in leak protection)
2. Second choice: OpenVPN UDP or TCP (well-tested, secure)
3. Avoid: PPTP (obsolete, insecure), L2TP (can leak)

Testing After Applying Fixes

After implementing the fixes above:

1. Restart your computer (essential for changes to take effect)
2. Reconnect to your VPN
3. Visit dovpn.com/ip-leak-test
4. Verify no leaks are detected
5. Test multiple times over a few minutes to ensure consistency
6. Test with different VPN servers

Frequently Asked Questions

How do I test for IP leaks on Windows 10 or Windows 11?

Connect to your VPN on Windows, then visit dovpn.com/ip-leak-test in your browser. The tool will automatically check for IPv4, IPv6, DNS, and WebRTC leaks. If it shows your real IP address or ISP instead of your VPN's, you have a leak.

Why does Windows leak my IP more than other operating systems?

Windows has several features that can bypass VPNs: Teredo tunneling (IPv6), Smart Multi-Homed Name Resolution (DNS), and Network Location Awareness. These features prioritize connection speed over privacy, which can cause leaks if not properly configured.

How do I disable IPv6 on Windows to prevent leaks?

Open Control Panel → Network and Internet → Network Connections. Right-click your active connection → Properties. Uncheck "Internet Protocol Version 6 (TCP/IPv6)" and click OK. Restart your computer and reconnect to your VPN.

Does Windows Defender block VPN connections?

Windows Defender doesn't block VPNs, but Windows Firewall can interfere with VPN connections. Ensure your VPN app is allowed through the firewall (Settings → Privacy & Security → Windows Security → Firewall → Allow an app through firewall).

What's the best VPN protocol for Windows to prevent leaks?

WireGuard and OpenVPN are the most reliable protocols for Windows. WireGuard is faster and has better built-in leak protection. Avoid PPTP and L2TP as they have known vulnerabilities.

Can Windows updates cause new IP leaks?

Yes, Windows updates can sometimes re-enable IPv6, Teredo, or reset network settings, causing leaks to return. After major Windows updates, re-test your VPN for leaks and reapply fixes if necessary.

Do I need to disable IPv6 if my VPN supports it?

If your VPN fully supports IPv6 routing (check your provider's documentation), you don't need to disable it. However, if you're unsure or experience IPv6 leaks, disabling IPv6 is the safest option.

Conclusion: Secure Your Windows VPN

Windows 10 and Windows 11 have multiple features that can cause IP leaks despite using a VPN. By understanding Windows-specific vulnerabilities and applying the fixes in this guide, you can ensure your VPN properly protects your privacy.

Key takeaways:

• Windows has built-in features (Teredo, SMHNR) that bypass VPNs and leak IPs
• Disable IPv6 and Teredo to prevent the most common Windows leaks
• Enable your VPN's kill switch to prevent reconnection leaks
• Test regularly using dovpn.com/ip-leak-test
• Retest after Windows updates as settings can reset

Need a Better VPN for Windows?

If your current VPN continues leaking despite these fixes, it may be time to switch to a VPN with better Windows compatibility and leak protection: