What a DNS leak is (and why it matters)

A DNS leak occurs when your device sends DNS queries to a resolver that is not the one you intend to be protected by your VPN or other secure routing. Even if your browsing traffic is encrypted, the domain lookups can still reveal information about where you’re connecting.

This matters most when your VPN (or secure connection) is configured to tunnel traffic, but DNS is handled separately or falls back to a local or ISP resolver. The practical goal is to make sure DNS resolution follows the same protections as the rest of your traffic.

A simple model: “Where do DNS questions go?”

Think of DNS protection as a “path” problem:

  1. Your device asks for a domain (e.g., example.com).
  2. Your operating system sends that query to a DNS resolver.
  3. You want that resolver choice and routing to remain within the secure channel you trust.

Protecting yourself against DNS leaks means ensuring that step (2) and the network path in step (3) cannot bypass your intended tunnel.

Core ways to reduce DNS-leak risk

1) Use encrypted DNS on the device

If your device uses encrypted DNS such as DNS over HTTPS (DoH) or DNS over TLS (DoT), the DNS query should be protected in transit. This can reduce exposure when traffic is intercepted, and it can also help prevent plain-text DNS from being visible on the local network.

Note: encrypted DNS does not automatically guarantee “no leaks.” You still need to verify that the encrypted resolver is reachable through the intended route.

2) Make DNS go through the VPN tunnel

On many systems, DNS handling can involve OS settings, VPN-provided DNS resolvers, and “DNS fallback” behaviors. DNS leaks are often caused by mismatches between:

  • the DNS servers your VPN expects to use, and
  • the DNS servers your device actually queries when the connection starts, changes, or reconnects.

To reduce the chance of mismatch, ensure your VPN is using the DNS handling mode you expect (for example, routing/redirecting DNS through the tunnel, if available) and avoid configurations that allow DNS to use local resolvers.

3) Recheck after reconnects and configuration changes

DNS-related settings can become stale after:

  • VPN reconnects,
  • network changes (Wi‑Fi to mobile),
  • changing encrypted DNS settings,
  • changing split-tunnel or firewall rules.

A practical mitigation is to reconnect the VPN and then re-verify DNS behavior afterward, rather than assuming it stayed correct.

Differences and limits to understand

Split tunneling and routing choices can change DNS behavior

If only some traffic is sent through the secure tunnel, DNS queries may follow a different path than you expect. Whether DNS leaks occur depends on how your platform and network stack route DNS under your specific configuration.

“No leak” tools may disagree

DNS leak checks typically observe which resolvers you reach or what answers you receive. Different tools may:

  • use different test domains,
  • interpret results differently,
  • be affected by caching or partial connectivity. So, treat confirmations as probabilistic unless you can validate across more than one method.

IPv4 vs IPv6 can behave differently

Even when DNS over one IP family looks correct, the other family may not. Some environments route IPv6 differently, so you should consider testing both where applicable.

Practical checks you can run yourself

  1. Connect to your VPN and then perform a DNS-leak test.
  2. If you use encrypted DNS (DoH/DoT), confirm the results still look consistent with your intended resolver path.
  3. After any reconnect or network change, repeat the test to ensure the behavior did not regress.
  4. If you suspect split tunneling or local DNS fallback, check your device and VPN DNS settings for consistency.

If results vary, the most likely causes are stale DNS settings after reconnects, resolver path mismatches, or routing differences (such as split tunneling or IPv6 behavior).