The Domain Name System (DNS) is often compared to the phonebook of the internet. It translates human-friendly domain names, such as obfusgated.com, into numerical IP addresses that servers use to communicate. Whenever you type a web address into your browser or click a link, your device sends a DNS query to a DNS server (or resolver) to get the IP address of that website.
When using a VPN or a proxy, all your internet traffic is supposed to go through the secure tunnel or proxy server, including DNS requests. However, if DNS traffic bypasses that tunnel, it’s known as a DNS leak. In this scenario, your real IP address, location, or visited domains may be exposed to third parties, defeating the anonymity and privacy that a VPN or proxy is meant to provide.
What is a DNS Leak
A DNS leak occurs when your device sends DNS queries outside the secure tunnel of your VPN or the chain of your proxy setup, usually to your Internet Service Provider’s (ISP) default DNS servers. This can happen for several reasons, including:
VPN Misconfiguration: Incorrect network or DNS settings within the VPN client may cause your operating system to default to a non-VPN DNS server.
Fallback Behavior: If the primary DNS server fails or times out, some systems attempt to use another DNS server, which might be an unencrypted or ISP-provided resolver.
Operating System Issues: Certain operating systems have built-in DNS caching or “smart” multi-interface capabilities that can inadvertently route DNS traffic outside the VPN tunnel.
Third-Party DNS Services: Manually configuring public DNS (e.g., Google Public DNS, Cloudflare, or OpenNIC) can sometimes override your VPN’s DNS leak protection if not set up properly.
DNS over HTTPS (DoH) or DNS over TLS (DoT): If your browser or device is configured to use encrypted DNS independently, it might bypass your VPN’s DNS settings altogether, leading to leaks.
Why DNS Leaks Are a Threat to Your Privacy
One of the key reasons people use VPNs or proxies is to protect their online privacy and anonymity. If DNS queries bypass the secure connection, your internet activity can be exposed to your ISP, public Wi-Fi operators, or surveillance entities. A DNS leak can reveal:
Your real IP address
The domains or websites you visit
Your approximate physical location
This effectively undermines the purpose of using a VPN or proxy, leaving you open to tracking, profiling, or location-based restrictions. Even if your actual IP address is hidden by the VPN, the IP address of your real DNS server (usually operated by your ISP) can reveal your location and browsing activity to third parties.
Why DNS Leaks Occur
Many VPN and proxy users assume that all aspects of their traffic are automatically secured. In reality, misconfigured DNS settings or poor VPN software design can still lead to DNS requests leaking outside the secure channel. Some providers might rely on public DNS servers (e.g., Google DNS), but if the connection to that DNS server isn’t tunneled correctly, your ISP or other entities can still intercept and view DNS traffic.
Additionally, some operating systems, browser settings, or security software may enforce their own DNS preferences, inadvertently bypassing your VPN. For instance, advanced features like DNS over HTTPS (DoH) can encrypt DNS requests independently from the VPN, which in turn might route DNS queries outside of the VPN tunnel.
Tips to Prevent DNS Leaks
The best strategy to avoid DNS leaks is a multi-layered approach. Below are some key measures you can take to safeguard against DNS leaks:
Use a VPN with DNS Leak Protection: Many reputable VPN providers include built-in DNS leak prevention features that force DNS queries through the VPN tunnel. For example, services like Proton VPN and Mullvad implement their own DNS servers and firewall rules to block external DNS requests.
Manually Configure DNS Servers (When Necessary): Specify secure, non-logging DNS resolvers (e.g., Quad9, Cloudflare, or your VPN provider’s own DNS) in your operating system or network settings only if your VPN supports it. Otherwise, using third-party DNS can override your VPN’s settings, increasing the risk of leaks.
Disable Smart Multi-Homing or Fallback DNS: Some operating systems (like Windows or certain Linux distributions) automatically switch to alternative DNS resolvers. Disabling or properly configuring these features can reduce leaks.
Keep Your VPN Software Updated: Older VPN clients may have bugs that lead to DNS leaks. Regularly update your VPN software to benefit from the latest security fixes and leak protection improvements.
Kill Switch / Network Lock: If your VPN connection drops, a kill switch ensures your device cannot send or receive traffic (including DNS requests) outside the VPN tunnel.
Check Browser Settings (DNS over HTTPS/TLS): Browsers like Firefox, Chrome, Edge, and Brave often have a “Secure DNS” or “DNS over HTTPS” toggle. When activated, this may bypass the DNS server provided by your VPN. Disable Secure DNS in your browser if you want the VPN to handle DNS requests.
Avoid Conflicting VPNs or Security Software: Running multiple VPN services, antivirus programs with their own DNS filters, or firewall tools like Little Snitch or Portmaster can introduce DNS conflicts and potential leaks.
Common DNS Leak Scenarios and How to Fix Them
DNS leaks can happen in different environments. Below are some common scenarios along with suggested solutions.
1. Manually Set DNS in Your Operating System
If you have manually specified a third-party DNS server (e.g., Google DNS, Cloudflare) in your operating system settings, this may override your VPN’s DNS settings.
Windows: Under Network Connections → (Wi-Fi or Ethernet) → Properties → TCP/IPv4 or TCP/IPv6 → Properties, ensure “Obtain DNS server address automatically” is selected when using a VPN that auto-configures DNS. Then, flush your DNS cache with this command:
ipconfig /flushdns
macOS: Go to System Settings → Network → (Wi-Fi or Ethernet) → Details… → DNS, and remove any manually added DNS entries. Then flush the DNS cache in Terminal:
sudo killall -HUP mDNSResponder
Linux: Check your distribution’s network manager settings or /etc/resolv.conf to ensure there are no hard-coded nameserver lines that override your VPN’s DNS. If your system uses systemd-resolved, verify it’s forwarding DNS queries to your VPN’s DNS servers by examining /etc/systemd/resolved.conf (or /etc/systemd/resolved.conf.d/*.conf) and ensuring the correct DNS is set.
If your VPN client doesn’t integrate well with systemd-resolved, you could disable it with:
Then remove or update the symlink /etc/resolv.conf and manually set your VPN’s DNS in a plain-text /etc/resolv.conf. Be aware this can break DNS if not done correctly.
On distributions that don’t use systemd-resolved, remove or comment out any custom nameserver lines in /etc/resolv.conf or set them to your VPN’s DNS directly.
Android (9+): Disable “Private DNS” if it points to a specific provider. Go to Settings → Network & internet → Private DNS → Off.
iOS: iOS typically does not allow global DNS changes unless you install a configuration profile or use a “dummy VPN” app. Make sure any custom DNS profiles are removed if relying on your VPN’s DNS.
2. Browser-Level DNS Over HTTPS (DoH)
Modern browsers often include DNS over HTTPS, which encrypts DNS requests directly to a third-party resolver, bypassing your VPN’s DNS settings. To disable DoH or Secure DNS:
Firefox: Go to Menu → Settings → Privacy & Security → scroll down to DNS over HTTPS → select “Off.”
Chrome/Brave/Opera: Go to Settings → Privacy & Security → Security → disable “Use secure DNS.”
Microsoft Edge: Settings → Privacy, search, and services → Security → turn off “Use secure DNS to specify how to lookup the network address for websites.”
Safari: Currently doesn’t support DoH in the same way, but Apple may change this in future releases.
3. VPN Disconnects or Fallback
If your VPN connection drops and you continue browsing, DNS queries may revert to your ISP’s servers. To avoid this:
Enable the Kill Switch (sometimes called “Network Lock”) in your VPN client so all internet traffic is blocked unless the VPN is connected.
Make sure your VPN client automatically restarts if the connection fails, so you don’t accidentally browse with your real DNS.
4. VPN Protocol-Specific Considerations
Different VPN protocols handle DNS differently:
OpenVPN: As of version 2.3.9, you can add
block-outside-dns
to the configuration file (on Windows) to prevent DNS leaks.
WireGuard: Ensure the
[Interface]
section of your WireGuard config has a valid
DNS = A.B.C.D
entry. This will direct DNS queries to your VPN provider’s DNS or your chosen secure DNS.
How to Test for DNS Leaks
Even if you take precautions, it’s crucial to test your setup. You can use online DNS leak testing tools, or your VPN provider’s own connection checker, to ensure all DNS requests go through the secure tunnel. A simple test involves:
Testing Without a VPN or Proxy First — to see your default DNS servers. Take note of which DNS servers show up, as you’ll use this information for comparison when connected to your VPN or proxy.
Connecting to Your VPN or Proxy — preferably in another country to make potential leaks more obvious.
Visiting a DNS Leak Test Page — go to the DNS leak test page to see what DNS servers serve your queries.
Comparing the Reported DNS Servers — they should match your VPN or proxy’s DNS servers rather than the ones you noted prior or your ISP’s defaults.
Run the DNS leak test multiple times with and without VPN and across different network connections or Wi-Fi hotspots to ensure consistent DNS leak protection.
Conclusion
DNS leaks pose a significant threat to your online privacy, potentially revealing your real location and browsing habits. While VPNs and proxies aim to secure and anonymize your web traffic, it’s just as important to ensure that DNS queries are handled within the same secure environment. By choosing a reliable VPN provider with leak protection and routinely testing for leaks, you can significantly reduce the risk of having your private data exposed. With the right precautions, your DNS queries will remain safely within the encrypted tunnel, keeping your identity and online activities hidden from prying eyes.
FAQ
A DNS leak occurs when your internet queries bypass your VPN or proxy’s secure tunnel and go directly to a DNS server, often revealing your real IP address and location. This compromises the privacy and anonymity a VPN or proxy is meant to provide.
DNS leaks undermine the purpose of using a VPN or proxy by exposing the domains you visit and potentially your real location to your ISP, websites, or malicious third parties. In short, your browsing is no longer private.
When your device sends DNS requests to your ISP’s resolver, your real IP and geographical details can be logged. Even if the rest of your traffic is encrypted, these leaked DNS queries can give away your approximate location.
No. While many premium VPN providers offer built-in “DNS leak protection,” not all providers implement it effectively. Always verify that your VPN software has this feature and is configured correctly.
Not necessarily. Proxies often only redirect HTTP or SOCKS traffic, meaning DNS requests might still go through your default DNS server. To fully prevent leaks, a VPN or a secure DNS configuration is typically more effective.
You can visit the specialized DNS leak testing tool on our website. First, disconnect from your VPN or proxy and run the test to identify your default DNS servers — typically provided by your ISP. Take note of these. Then, connect to your VPN or proxy and run the test again. If the displayed DNS servers still match your ISP’s or the ones you saw earlier, you may have a DNS leak. A successful test should only show DNS servers associated with your VPN or proxy, often located in the same region as your VPN server.
Yes. Streaming platforms and other geo-restricted services can detect your real location from DNS queries. If you experience unexpected blocks, you may have a DNS leak undermining your VPN’s location spoofing.
Immediately stop using the VPN or proxy session. Then, update or reconfigure your VPN software, enable any built-in DNS leak protection, and ensure your DNS server is properly tunneled. Test again to confirm the leak is fixed.
