DNS Leak Guide

DNS leaks are one of the most common and dangerous VPN privacy failures. Unlike IP leaks that expose your location, DNS leaks reveal your complete browsing history to your Internet Service Provider (ISP) — even when using a VPN. This comprehensive guide explains what DNS leaks are, why they're often worse than IP leaks, how to detect them, and how to fix DNS leaks on Windows, Mac, iOS, and Linux.

Understanding DNS (Domain Name System)

Before understanding DNS leaks, you need to understand what DNS is and why it matters for privacy.

What Is DNS?

DNS (Domain Name System) is often called "the internet's phonebook." When you type a website address like "facebook.com" or "google.com" into your browser, your device doesn't actually know where to find that website. It needs to translate the human-readable name into a machine-readable IP address.

Here's how it works:

1. You type "netflix.com" in your browser
2. Your device sends a DNS query asking: "What's the IP address for netflix.com?"
3. A DNS server responds: "netflix.com is at 54.173.225.234"
4. Your device connects to that IP address
5. Netflix loads in your browser

Analogy: DNS is like asking for directions. Instead of memorizing the street address (IP) of every place you want to visit, you just ask someone (DNS server) "Where's the coffee shop?" and they tell you the address.

Who Runs DNS Servers?

DNS servers can be operated by:

• Your ISP: Comcast, Verizon, AT&T, etc. (default for most users)
• Your VPN provider: NordVPN, Surfshark, ExpressVPN have their own DNS servers
• Public DNS services: Google (8.8.8.8), Cloudflare (1.1.1.1), Quad9 (9.9.9.9)
• Your employer or school: Corporate/educational networks often run DNS

The Privacy Problem

Whoever runs your DNS server can see every website you visit.

When you make a DNS query, the DNS server logs:

• Which websites you're visiting (facebook.com, amazon.com, etc.)
• When you visit them (timestamps)
• How often you visit (frequency)
• Your IP address (identifying you)

This creates a complete record of your browsing history — and it's often unencrypted, making it easy to intercept or log.

What Is a DNS Leak?

A DNS leak occurs when your DNS queries are sent to your ISP's DNS servers (or other third-party DNS servers) instead of your VPN provider's DNS servers, even though you're connected to a VPN.

How VPNs Should Handle DNS

✅ VPN working correctly (no DNS leak):

1. You connect to your VPN
2. All traffic — including DNS queries — routes through the VPN tunnel
3. DNS queries go to your VPN provider's DNS servers
4. Your ISP sees encrypted VPN traffic (can't see which websites you're visiting)
5. Only your VPN provider knows your DNS queries

❌ DNS leak (VPN failing):

1. You connect to your VPN
2. Your VPN encrypts your web traffic
3. But DNS queries bypass the VPN tunnel
4. DNS queries go to your ISP's DNS servers
5. Your ISP sees every website you visit (via DNS logs)
6. Your VPN protects your IP, but your browsing history is exposed

Real-World Example

Scenario: You're using a VPN to hide your browsing from your ISP. You visit several websites.

Without DNS leak:

• Your ISP sees: "User connected to VPN server in Netherlands"
• Your ISP can't see which websites you visit
• Only your VPN provider knows you visited facebook.com, twitter.com, etc.

With DNS leak:

• Your ISP sees: "User connected to VPN server in Netherlands"
• Your ISP also sees DNS queries: facebook.com, twitter.com, torrent-site.com, etc.
• Your ISP has a complete log of every website you visited
• Your VPN did nothing to protect your privacy

Why DNS Leaks Are Extremely Dangerous

DNS leaks are often more dangerous than IP leaks for several reasons:

1. Exposes Your Complete Browsing History

IP leaks reveal WHERE you are (location, ISP).
DNS leaks reveal WHAT you're doing (every website you visit).

Your ISP can build a comprehensive profile:

• Political views (which news sites you visit)
• Health conditions (medical sites you research)
• Shopping habits (e-commerce sites you browse)
• Entertainment preferences (streaming sites, adult content)
• Financial information (banking sites, crypto exchanges)
• Communication patterns (email, messaging platforms)

2. ISPs Actively Log and Sell DNS Data

In many countries (including the United States), ISPs are legally allowed to:

• Log all DNS queries indefinitely
• Sell DNS data to advertisers and data brokers
• Share DNS logs with government agencies (often without warrants)
• Monetize your browsing history

Real example: In 2017, the US Congress repealed ISP privacy rules, allowing ISPs to sell your browsing history without consent. DNS logs are a primary source of this data.

3. DNS Leaks Are Very Common

DNS leaks are more common than IP leaks because:

• Many VPNs don't properly configure DNS settings
• Operating systems (especially Windows) have features that cause DNS leaks
• ISPs sometimes hijack DNS queries regardless of configuration
• Most users don't realize they're leaking DNS

4. DNS Leaks Can Persist Even After Fixing IP Leaks

You can have perfect IP leak protection while simultaneously having DNS leaks. Your VPN successfully hides your IP address, but your ISP still sees every website you visit.

Many users check their IP and assume their VPN is working — but never check for DNS leaks.

5. Legal and Security Implications

DNS leaks can have serious consequences:

• Copyright enforcement: ISPs log DNS queries to torrent trackers, then forward DMCA notices
• Government surveillance: Authorities can subpoena ISP DNS logs (easier than VPN logs)
• Censorship bypass failure: In restrictive countries, DNS leaks expose forbidden site access
• Targeted advertising: Advertisers purchase DNS data to profile and target you
• Data breaches: ISPs have been hacked, exposing DNS logs containing user browsing histories

How DNS Leaks Happen

DNS leaks occur for several technical reasons:

1. VPN Software Doesn't Configure DNS Properly

When you connect to a VPN, the VPN app should:

1. Detect your current DNS servers (usually your ISP's)
2. Replace them with the VPN provider's DNS servers
3. Route all DNS queries through the VPN tunnel

The problem: Some VPN apps fail to properly configure DNS settings, leaving your ISP's DNS servers active.

2. Smart Multi-Homed Name Resolution (Windows)

This is the #1 cause of DNS leaks on Windows.

Windows has a feature called "Smart Multi-Homed Name Resolution" (SMHNR) that sends DNS queries to all available network interfaces simultaneously and uses whichever responds first.

What happens:

1. You connect to VPN
2. Windows now has two network interfaces: VPN + regular internet
3. Windows sends DNS query to both your VPN's DNS AND your ISP's DNS
4. Your ISP's DNS often responds faster (it's closer geographically)
5. Windows uses your ISP's DNS response
6. DNS leak occurs despite VPN being "connected"

3. ISP DNS Hijacking (Transparent DNS Proxies)

Some ISPs intercept all DNS traffic on port 53 (the standard DNS port) regardless of destination. This is called a "transparent DNS proxy."

How it works:

1. Your device sends DNS query to VPN provider's DNS (e.g., 10.8.0.1)
2. Your ISP intercepts the query before it reaches the VPN
3. ISP responds with their own DNS answer
4. You think you're using VPN DNS, but you're actually using ISP DNS

Common ISPs that do this: Comcast, Spectrum, some mobile carriers

4. Manual DNS Configuration

If you've manually set DNS servers in your OS settings (like Google's 8.8.8.8 or Cloudflare's 1.1.1.1), those settings may override your VPN's DNS configuration.

5. IPv6 DNS Leaks

If your VPN routes IPv4 DNS but not IPv6 DNS, all IPv6 DNS queries leak to your ISP.

6. Network Transition Leaks

When switching networks (Wi-Fi to cellular, or between Wi-Fi networks), DNS settings can temporarily revert to defaults before VPN reconnects.

How to Detect DNS Leaks

Step 1: Check Your Real DNS Servers (Without VPN)

1. Disconnect from your VPN
2. Visit dovpn.com/ip-leak-test
3. Note the DNS servers shown (these are your ISP's DNS servers)

Example: You might see DNS servers like:

• 75.75.75.75 (Comcast)
• 8.8.8.8 (Google Public DNS)
• Your router's IP (e.g., 192.168.1.1)

Step 2: Connect to Your VPN

1. Connect to your VPN
2. Choose a server in a different country
3. Wait for full connection

Step 3: Run DNS Leak Test

1. Visit dovpn.com/ip-leak-test
2. Check the DNS servers section
3. Compare with your baseline from Step 1

Step 4: Interpret Results

✅ No DNS leak (VPN working):

• DNS servers belong to your VPN provider (not your ISP)
• DNS servers are in the same location as your VPN server
• No ISP DNS servers appear

❌ DNS leak detected:

• Your ISP's DNS servers appear
• Google/Cloudflare public DNS appears (when you didn't configure it)
• Multiple DNS servers from different providers appear
• DNS servers are in your real location (not VPN location)

Fixing DNS Leaks on Windows

Fix #1: Enable VPN DNS Leak Protection

1. Open your VPN app settings
2. Look for "DNS Leak Protection" or "Use VPN DNS"
3. Enable it
4. Reconnect to VPN
5. Test for DNS leaks

Fix #2: Disable Smart Multi-Homed Name Resolution

⚠️ Warning: This requires editing the Windows Registry. Back up your registry first.

1. Press Windows Key + R
2. Type regedit and press Enter
3. Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters
4. Right-click → New → DWORD (32-bit) Value
5. Name: DisableSmartNameResolution
6. Double-click → Set value to 1
7. Click OK
8. Restart your computer
9. Reconnect to VPN and test

Fix #3: Flush DNS Cache

1. Open Command Prompt (Run as Administrator)
2. Run: ipconfig /flushdns
3. Reconnect to VPN
4. Test for DNS leaks

Fix #4: Manually Set VPN DNS Servers

1. Press Windows Key + R → type ncpa.cpl → Enter
2. Right-click your VPN connection → Properties
3. Select "Internet Protocol Version 4 (TCP/IPv4)" → Properties
4. Select "Use the following DNS server addresses"
5. Enter your VPN provider's DNS servers (check their docs) or:
   • Cloudflare: 1.1.1.1 and 1.0.0.1
   • Quad9: 9.9.9.9 and 149.112.112.112
6. Click OK
7. Flush DNS cache
8. Reconnect and test

More details: See our complete Windows leak fixing guide.

Fixing DNS Leaks on Mac

Fix #1: Enable VPN DNS Protection

1. Open your VPN app settings
2. Enable "DNS Leak Protection" or similar
3. Reconnect to VPN
4. Test for DNS leaks

Fix #2: Flush DNS Cache

1. Open Terminal
2. Run: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
3. Enter your password
4. Reconnect to VPN
5. Test for DNS leaks

Fix #3: Manually Set DNS Servers

1. System Settings → Network
2. Select your connection → Details (or Advanced)
3. Go to DNS tab
4. Click + and add your VPN's DNS servers or privacy-focused DNS:
   • Cloudflare: 1.1.1.1 and 1.0.0.1
   • Quad9: 9.9.9.9 and 149.112.112.112
5. Remove existing DNS servers (select and click -)
6. Click OK → Apply
7. Flush DNS cache and test

More details: See our complete Mac leak fixing guide.

Fixing DNS Leaks on iPhone/iPad

Fix #1: Enable VPN DNS Protection

1. Open your VPN app
2. Go to Settings
3. Enable "DNS Leak Protection" or "Use VPN DNS"
4. Reconnect to VPN
5. Test for DNS leaks

Fix #2: Disable iCloud Private Relay

iCloud Private Relay can interfere with VPN DNS:

1. Settings → Apple ID → iCloud → Private Relay
2. Turn Off Private Relay
3. Reconnect to VPN
4. Test for DNS leaks

Fix #3: Use DNS over HTTPS in Safari

1. Settings → Safari → Advanced → DNS
2. Enable DNS over HTTPS (if available in your iOS version)
3. Select a privacy-focused provider

More details: See our complete iPhone leak fixing guide.

Fixing DNS Leaks on Linux

Fix #1: Configure DNS via /etc/resolv.conf

1. Edit DNS configuration:

sudo nano /etc/resolv.conf

2. Replace contents with your VPN's DNS or:

   nameserver 1.1.1.1
   nameserver 1.0.0.1

3. Save and exit (Ctrl+X, Y, Enter)
4. Reconnect to VPN and test

Fix #2: Use systemd-resolved

For modern Linux distributions using systemd:

sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved

Then configure /etc/resolv.conf manually.

Fix #3: Verify DNS with dig

Test which DNS server is actually being used:

dig +short myip.opendns.com @resolver1.opendns.com

Advanced DNS Leak Prevention

1. Use DNS over HTTPS (DoH)

DNS over HTTPS encrypts DNS queries at the application level, preventing ISP interception:

• Firefox: Settings → Privacy & Security → Enable DNS over HTTPS
• Chrome: Settings → Privacy and security → Security → Use secure DNS
• Edge: Settings → Privacy → Security → Use secure DNS

2. Use DNS over TLS (DoT)

Similar to DoH but operates at the transport layer. Supported by:

• Android 9+: Settings → Network → Private DNS
• Linux with systemd-resolved

3. Monitor DNS Queries

Tools to monitor DNS activity:

• Windows: Wireshark, Process Monitor
• Mac: Little Snitch, Wireshark
• Linux: tcpdump, Wireshark

4. Use VPN with Built-in DNS Leak Protection

Choose VPNs that automatically prevent DNS leaks:

• NordVPN (CyberSec DNS)
• Surfshark (CleanWeb DNS)
• ProtonVPN (NetShield DNS)
• ExpressVPN (TrustedServer DNS)

Frequently Asked Questions

What is a DNS leak?

A DNS leak occurs when your DNS queries (requests to translate website names into IP addresses) are sent to your ISP's DNS servers instead of your VPN's DNS servers, even though you're connected to a VPN. This exposes your complete browsing history to your ISP.

How do I know if I have a DNS leak?

Connect to your VPN, then visit dovpn.com/ip-leak-test and check the DNS servers section. If you see your ISP's DNS servers (not your VPN provider's), you have a DNS leak.

Are DNS leaks worse than IP leaks?

DNS leaks can be worse for long-term privacy because they expose your complete browsing history to your ISP, while IP leaks expose your location. DNS leaks are also more common and harder to detect.

Can DNS leaks happen with premium VPNs?

Yes, even paid VPN services can experience DNS leaks due to OS configuration issues, ISP DNS hijacking, or VPN software bugs. Regular testing is essential regardless of which VPN you use.

How do I fix DNS leaks?

Enable your VPN's DNS leak protection, manually set DNS servers to your VPN provider's DNS, flush your DNS cache, and on Windows, disable Smart Multi-Homed Name Resolution via registry edit.

Can my ISP still see my DNS queries with a VPN?

If you have a DNS leak, yes. If your VPN properly prevents DNS leaks, your ISP only sees encrypted VPN traffic and cannot see which websites you're visiting via DNS queries.

What's the difference between DNS leak and IP leak?

IP leaks expose your IP address (location and ISP). DNS leaks expose your DNS queries (which websites you visit). You can have one without the other, or both simultaneously. Read our complete comparison guide.

Conclusion: Protect Your DNS Privacy

DNS leaks are one of the most common and dangerous VPN privacy failures. They expose your complete browsing history to your ISP, advertisers, and potentially government agencies — defeating the entire purpose of using a VPN.

Key takeaways:

• DNS leaks expose your browsing history (often worse than IP leaks)
• DNS leaks are very common, especially on Windows
• Enable VPN DNS leak protection and test regularly
• Disable Windows Smart Multi-Homed Name Resolution
• Flush DNS cache after making changes
• Use DNS over HTTPS for additional protection

Need a VPN That Prevents DNS Leaks?

Choose a VPN with comprehensive DNS leak protection: