What Is a DNS Leak and How to Test It

What Is DNS?

Before understanding DNS leaks, you need to understand DNS itself. The Domain Name System (DNS) is like the internet’s phone book—it translates human-readable domain names (like brovpn.io) into IP addresses (like 192.168.1.1) that computers use.

Every time you visit a website, your device makes a DNS query to find the correct IP address.

What Is a DNS Leak?

A DNS leak occurs when your DNS queries bypass your VPN tunnel and go directly to your ISP’s DNS servers instead of your VPN provider’s servers.

Without VPN:

Your Device → ISP DNS Server → Website
(ISP sees all your queries)

With VPN (Properly Working):

Your Device → VPN Tunnel → VPN DNS Server → Website
(ISP sees encrypted traffic only)

With VPN (DNS Leak):

Your Device → VPN Tunnel (for web traffic)
           → ISP DNS Server (DNS queries leak!)

Why DNS Leaks Are Dangerous

Even with a VPN, a DNS leak exposes:

1. Every website you visit - Your ISP sees your complete browsing history
2. Your real location - DNS servers can pinpoint your area
3. Browsing patterns - When you’re online, what you research
4. Potential for selling data - ISPs may sell browsing data
5. Vulnerability to tracking - Advertisers and third parties can profile you

Common Causes of DNS Leaks

1. Misconfigured VPN

Some VPN apps don’t properly configure DNS settings, leaving your system’s default DNS active.

2. IPv6 Leaks

Many VPNs only tunnel IPv4 traffic, letting IPv6 DNS queries leak.

3. Windows Smart Multi-Homed Name Resolution

Windows may query multiple DNS servers simultaneously, including non-VPN servers.

4. Transparent DNS Proxies

Some ISPs redirect all DNS traffic through their servers regardless of settings.

5. Manual DNS Configuration

If you’ve manually set DNS servers, they might override VPN DNS.

How to Test for DNS Leaks

Step 1: Connect to Your VPN

Ensure your VPN is active and connected.

Step 2: Visit a DNS Leak Test Site

Go to websites like:

• dnsleaktest.com
• ipleak.net
• browserleaks.com/dns

Step 3: Run the Test

Click “Extended Test” for thorough results.

Step 4: Analyze Results

No Leak: You see only your VPN provider’s DNS servers Leak Detected: You see your ISP’s DNS servers or your real location

How to Prevent DNS Leaks

Use a VPN with Built-in Leak Protection

Quality VPNs like BroVPN automatically:

• Route all DNS through encrypted tunnel
• Block non-VPN DNS requests
• Disable IPv6 if needed

Configure Your System

Windows:

1. Open Network Settings
2. Disable “Smart Multi-Homed Name Resolution”
3. Use VPN’s DNS servers only

macOS:

1. Network Preferences → Advanced → DNS
2. Remove non-VPN DNS servers
3. Let VPN manage DNS

Router Level: Configure your router to use secure DNS and prevent bypassing.

Use Private DNS

Configure DNS-over-HTTPS (DoH) or DNS-over-TLS (DoT) for extra protection.

Testing Checklist

Before trusting your VPN connection:

• Run DNS leak test with VPN connected
• Verify no ISP DNS servers appear
• Test from multiple browsers
• Check after reconnecting
• Test on different networks

BroVPN DNS Protection

BroVPN automatically protects against DNS leaks by:

• Routing all DNS through encrypted tunnels
• Using private, no-log DNS servers
• Blocking DNS requests outside the tunnel
• Supporting both IPv4 and IPv6

Get protected with BroVPN:

1. Open @bro_vpn_bot
2. Get your configuration
3. Connect and stay leak-free

Legal Note: Use VPN services in accordance with your local laws.

See Also

• IPv6 Leak: Why It Happens and What to Do
• How VPN Works: Tunnel, Encryption, and Routing
• What Your VPN Provider Can See
• Public Wi-Fi Security
• Security Features