A VPN can hide your IP address, but it doesn’t automatically guarantee that every part of your internet traffic is private. One of the most common privacy failures is a DNS leak, where your device keeps asking a third-party DNS resolver (often your ISP) to translate website names into IP addresses—even while the rest of your traffic is inside the VPN tunnel. The result is simple: someone other than your VPN provider can still see which sites you’re trying to reach, when you accessed them, and sometimes where you are. For privacy-conscious users, remote workers, and travellers on public Wi-Fi, that’s a big deal. For streamers, DNS problems can also cause region errors or inconsistent access. This guide explains what DNS leaks are, why they happen, how to test for them, and the most reliable ways to fix and prevent them.
What DNS is (and what it reveals about you)
DNS (Domain Name System) is the “address book” of the internet. When you type a website like example.com, your device asks a DNS resolver for the IP address so it can connect.
Even though DNS requests don’t usually include the full page you’re visiting, they can still reveal a lot:
- Domains you access: news sites, banks, health portals, adult sites, work tools, etc.
- Timing patterns: when you’re online, and how frequently you use certain services.
- Approximate location: DNS resolvers can be local (ISP-based) and strongly correlated with your region.
- Network identity: on home connections, DNS activity can often be tied to an account holder.
In many countries, ISPs and network administrators can log DNS queries for troubleshooting, analytics, or compliance. Even when content is encrypted (HTTPS), DNS lookups still happen before the encrypted connection is established—unless you use encrypted DNS technologies and route them correctly.
What is a DNS leak? (Definition and quick example)
A dns leak happens when DNS requests bypass your VPN tunnel and go to a DNS resolver outside the VPN (commonly your ISP’s DNS). This can occur even while your IP address appears to be in another country.
A quick real-world example:
- You connect to a VPN server in France.
- Your browsing traffic goes through the French VPN server (your public IP looks French).
- But your device still asks your UK ISP’s DNS servers to resolve domains.
- Your ISP can still see you looked up bbc.co.uk, gmail.com, and yourbank.com, at specific times.
In other words, your VPN is doing part of the job (IP masking) but not the whole job (preventing DNS exposure). Good VPN apps include DNS leak protection, but you should still test—especially after updates, OS changes, or network changes.
Why DNS leaks happen (most common causes)
DNS leaks are usually caused by misconfiguration, conflicting settings, or OS-level behaviour. The most frequent causes include:
- VPN app doesn’t force DNS through the tunnel: the app fails to push secure DNS settings or doesn’t lock them reliably.
- System “smart” DNS selection: some operating systems and routers prefer the fastest resolver and may fall back to ISP DNS when the network changes.
- IPv6 mismatches: a VPN that only tunnels IPv4 may leave IPv6 DNS requests (or IPv6 traffic) outside the tunnel.
- Split tunnelling rules: if certain apps bypass the VPN, their DNS queries may also bypass it depending on implementation.
- Multiple network adapters: virtual adapters from other VPNs, security tools, or virtual machines can create routing conflicts.
- Captive portals and public Wi-Fi: some hotspots intercept DNS to trigger login pages, and VPNs can behave unpredictably before authentication.
- Manual DNS settings: custom DNS entries (work DNS, parental control DNS, “smart DNS” services) can override the VPN’s DNS and create leakage.
IPv6: the leak multiplier many people miss
IPv6 is increasingly common on mobile networks and modern home ISPs. If your VPN provider doesn’t support IPv6 fully (or your app doesn’t handle it correctly), you can end up with:
- IPv6 DNS requests going to your ISP
- IPv6 connections bypassing the VPN entirely
This is why “IPv6 leak protection” (or full IPv6 tunnelling) matters, especially for travellers and anyone on newer broadband/mobile networks.
Encrypted DNS (DoH/DoT) can help—or cause surprises
Encrypted DNS technologies like DNS over HTTPS and DNS over TLS aim to stop networks from reading your DNS requests in transit. Standards include RFC 8484 (DNS over HTTPS) and RFC 7858 (DNS over TLS).
However, when used alongside a VPN, browser-based encrypted DNS can create unexpected behaviour:
- Your browser might send DNS directly to a public provider (bypassing the VPN’s DNS), creating a different kind of exposure.
- In corporate environments, DoH can break internal DNS resolution unless configured carefully.
The goal is consistency: DNS should be encrypted and routed where you expect (typically through the VPN tunnel, using the VPN’s resolvers or your chosen private resolvers).
How dangerous is a dns leak in real life?
A dns leak is primarily a metadata privacy problem. It doesn’t automatically expose the exact pages you read or the content of your messages (HTTPS still protects that), but it can reveal enough to be sensitive.
Here’s what a leak can realistically enable:
- ISP visibility into browsing intent: domains can be enough to infer behaviour (banking, job searching, medical research, dating apps).
- Correlation attacks: if your VPN IP is seen visiting a service, and your ISP DNS logs show the same service looked up at the same time, linking becomes easier.
- Workplace or campus monitoring: administrators can track DNS even if you’re using a VPN for web traffic.
- Censorship and filtering detection: in restrictive networks, DNS can be blocked or manipulated; leaks may expose what you’re attempting to reach.
What it usually doesn’t do by itself:
- Decrypt HTTPS content: DNS doesn’t give an attacker your passwords or message content.
- Replace end-to-end security: a VPN is not a substitute for HTTPS, MFA, or secure devices.
For many users, the risk is less about one single lookup and more about patterns over time. If you’re paying for a privacy tool, DNS should not be leaking outside the tunnel.
How to test for DNS leaks (step-by-step)
Testing takes a minute and gives you a clear pass/fail signal. Do it on every device you use with a VPN (laptop, phone, tablet), because behaviour can differ by OS and network.
Method 1: Use a DNS leak test website
- Disconnect your VPN.
- Open a private/incognito browser window (to reduce caching effects).
- Visit a reputable DNS leak testing site and note which DNS servers are detected.
- Connect to your VPN server (preferably in a different country from your real location).
- Run the test again.
- If the detected DNS servers still belong to your ISP or your local network, you likely have a leak.
What you want to see: DNS resolvers that belong to your VPN provider (or a resolver you intentionally configured) and are consistent with your VPN location.
Method 2: Quick manual check with system tools
You can also check which DNS servers your device is configured to use:
- Windows: look at your active adapter’s DNS servers in network settings, or use ipconfig /all.
- macOS: check DNS in Network settings, or use scutil –dns.
- Linux: inspect resolv.conf (or systemd-resolved status) and your VPN interface routes.
This doesn’t prove every query is tunnelling correctly, but it’s a good way to spot obvious misconfigurations—like an ISP DNS server hardcoded while the VPN is connected.
How to fix a dns leak (practical, reliable solutions)
If you confirm a dns leak, fix it methodically. Start with the VPN layer, then the OS, then the network. The right approach depends on why you’re leaking.
1) Use a VPN that provides DNS leak protection (and verify it)
At a minimum, look for these features in the VPN app settings:
- DNS leak protection: forces DNS queries through the tunnel and prevents OS fallback to ISP DNS.
- Kill switch: blocks traffic (including DNS) if the VPN drops unexpectedly.
- IPv6 support or IPv6 leak protection: either tunnels IPv6 properly or safely disables it while connected.
- Private DNS resolvers: ideally operated by the VPN provider or clearly documented third-party resolvers.
After enabling these, re-test on at least two networks (home and mobile hotspot is a good combo). Some leaks only show up when switching networks or waking a laptop from sleep.
2) Check for split tunnelling and app-level bypass
Split tunnelling can be useful (for example, letting local banking apps use your normal connection), but it can also create messy DNS outcomes.
- If your VPN offers split tunnelling, disable it temporarily and re-test.
- Check whether “exclude local traffic” or “LAN access” options are changing how DNS is handled.
- Be cautious with browser extensions that claim to provide VPN routing—extensions may not control system DNS at all.
3) Handle IPv6 properly (don’t guess)
If your VPN doesn’t support IPv6, disabling IPv6 at the device level can reduce leak risk. If your VPN does support it, ensure it’s enabled and tested.
- Best outcome: full IPv4 and IPv6 tunnelling, with DNS resolvers reachable only through the VPN.
- Acceptable fallback: IPv6 disabled while connected, if implemented cleanly by the VPN app.
Be aware that disabling IPv6 can occasionally affect certain networks or services, but for most users it’s seamless. The bigger problem is leaving IPv6 half-configured.
4) Set DNS explicitly (when the VPN app can’t enforce it)
Sometimes you need to override DNS at the OS level, especially on systems with persistent DNS policies or work profiles.
- Windows/macOS: set DNS to the VPN provider’s recommended resolvers (or a trusted resolver), then reconnect to the VPN and retest.
- Android: “Private DNS” (DoT) can be used, but be careful—if it points to a public resolver outside the VPN, your DNS may still be identifiable even if encrypted.
- iOS/iPadOS: custom DNS profiles can override VPN DNS. Remove or adjust profiles that force an external resolver.
Important limitation: manual DNS changes can help, but they don’t replace proper routing. The real fix is ensuring DNS requests can only exit via the VPN interface.
5) Review browser “Secure DNS” settings
Chrome, Edge, and Firefox can use DNS over HTTPS. That’s not automatically bad—but it must align with your VPN setup.
- If your browser is set to use a specific public DoH provider, it may send DNS outside your VPN’s DNS system.
- If you want browser DoH, consider “use current service provider” (where available) while connected to a VPN that supplies DNS securely.
- If you rely on the VPN’s DNS leak protection, turning off browser DoH can simplify troubleshooting.
6) Don’t ignore the router and “smart DNS” services
Some households use “smart DNS” for streaming or set custom DNS on the router for ad blocking/parental controls. This can interfere with VPN DNS handling.
- If the router forces DNS, devices may keep using it even while on VPN.
- Some VPNs can override router DNS; others can’t, depending on platform permissions.
If you need router-level control, consider running the VPN on the router itself (where supported) so DNS and traffic policies are consistent for the whole network.
How DNS leaks affect streaming, gaming, and everyday performance
DNS isn’t just a privacy topic—it also affects reliability. Streaming services and CDNs often use DNS-based routing to send you to the nearest server region. When your DNS location and your VPN IP location don’t match, you can see:
- Streaming errors: region mismatches or repeated captchas
- Slow start times: longer buffering before playback begins
- Wrong content region: you connect to a nearby CDN node based on ISP DNS rather than VPN location
From a performance standpoint, DNS lookups are small, but frequent. On a typical page load, your device may resolve multiple domains (site, analytics, images, ads). A well-implemented VPN DNS setup usually adds minimal overhead—often in the low single-digit milliseconds per lookup—while preventing ISP-level DNS logging. Poor routing or far-away resolvers can add noticeable delay, especially on high-latency connections like hotel Wi-Fi.
Best practices to prevent DNS leaks long-term
- Re-test after OS and VPN updates: network stacks change, and so do default DNS behaviours.
- Prefer full-tunnel configurations: only use split tunnelling when you understand which apps and DNS paths are excluded.
- Avoid stacking VPNs and network tools: multiple adapters and “security” DNS apps often create routing conflicts.
- Use a kill switch when privacy matters: it’s one of the few controls that can stop leaks during brief disconnects.
- Choose providers with transparent VPN Technology & Encryption details: look for clear documentation, modern protocols, and independently verified security claims.
If you’re troubleshooting a stubborn case, test on a different network (mobile hotspot), try a different VPN protocol in the app, and temporarily remove custom DNS settings. DNS issues are often caused by one conflicting setting rather than a single “broken” VPN.
Conclusion
A dns leak is one of the most common ways VPN users accidentally expose browsing metadata, even when their IP address looks protected. The fix is usually straightforward: use a VPN app with proper DNS leak protection, verify IPv6 handling, avoid conflicting DNS settings, and re-test after network changes. If privacy is your goal, treat DNS testing as routine maintenance—especially on laptops that move between home, work, and public Wi-Fi. For streaming and travel, consistent DNS routing also improves reliability by reducing location mismatches. The practical recommendation: choose a VPN with clearly documented DNS behaviour, enable leak protection features, and confirm results with a leak test before you assume you’re covered.
