DNS Leaks Explained: How They Happen and Why They Matter
A DNS leak happens when your device sends website lookup requests outside your VPN tunnel, usually to your internet provider’s DNS servers. Even if your web traffic is encrypted, DNS leaks can still reveal which sites you’re trying to access. In practice, DNS leaks are common, often misunderstood, and not always equally serious — but they do matter in the right threat models.
Why DNS leaks matter
Most people think a VPN “hides everything.” When they hear about DNS leaks, it sounds like total failure. The reality is more nuanced: DNS leaks don’t usually expose page contents, but they can expose intent — which domains you’re trying to reach.
Understanding DNS leaks helps you correctly evaluate VPN protection, avoid panic, and focus on the fixes that actually reduce risk.
- DNS leaks expose domain lookups, not full browsing content.
- They often occur during network changes, sleep/wake cycles, or misconfiguration.
- Most modern VPNs try to prevent them, but implementations vary.
- They matter most on public Wi-Fi and for privacy-sensitive use.
- Reality anchor: DNS leaks reduce privacy, not total security.
How DNS works (plain English)
DNS (Domain Name System) is the internet’s address book. When you type a website name, your device asks a DNS server, “What IP address does this domain use?”
By default, that DNS server is usually provided by your ISP, your Wi-Fi network, or your operating system.
How DNS leaks happen
- Split routing: Traffic goes through the VPN, but DNS queries don’t.
- OS-level DNS overrides: The system ignores VPN DNS settings.
- Network changes: Switching Wi-Fi or waking from sleep breaks routing.
- IPv6 handling: DNS queries escape over IPv6 when VPNs only cover IPv4.
- Browser or app behavior: Some apps bypass system DNS entirely.
What DNS leaks do — and don’t expose
They can expose
- Which domains you attempt to visit
- Timing and frequency of requests
- Your real network (ISP or Wi-Fi operator)
They do not expose
- Full page content (HTTPS still encrypts this)
- Passwords or form data
- What you do inside logged-in accounts
What this means for real users
Everyday home users
DNS leaks at home are usually low-risk. Your ISP already knows you’re online, and HTTPS protects content. Still, leaks undermine the reason many people use a VPN.
Public Wi-Fi & travel
On cafés, hotels, and airports, DNS leaks matter more. They allow the local network operator to see which sites you’re querying.
Privacy-sensitive users
If your threat model includes minimizing metadata exposure, DNS leaks should be fixed. They create a partial trail even when traffic is encrypted.
Common myths vs reality
Myth #1: “A DNS leak means my VPN failed completely.”
Reality: It’s a partial failure, not total exposure.
Myth #2: “DNS leaks expose passwords.”
Reality: HTTPS still encrypts content.
Myth #3: “Only bad VPNs have DNS leaks.”
Reality: OS behavior and network changes cause leaks even with good VPNs.
Myth #4: “Kill switches stop all DNS leaks.”
Reality: Kill switches help, but DNS handling still matters.
Myth #5: “Fixing DNS makes me anonymous.”
Reality: It reduces one signal; identity still leaks elsewhere.
Where VPN tools and settings fit in
Most modern VPNs include DNS leak protection, but behavior varies by platform. Some route DNS through the tunnel; others use encrypted DNS resolvers.
Limitations and uncertainty
- DNS behavior differs across operating systems
- IPv6 support remains inconsistent
- Apps may bypass system DNS settings
FAQ
- Are DNS leaks common? Yes, especially during network changes.
- Should I worry about them? It depends on your threat model.
- Does a kill switch fix DNS leaks? It helps, but doesn’t guarantee prevention.
- Are mobile VPNs worse? Mobile OS networking behavior can increase leak risk.
- What should I do next? Test and verify: How to test your VPN.
Disclosure & methodology
Methodology: How we evaluate VPNs • Affiliate disclosure: How this site makes money
This article is educational. DNS behavior varies by device, OS, network, and VPN configuration.