Direct answer

DNS leaks refer to a situation where DNS lookups (the domain-to-IP “translation” step) are not handled exclusively through the intended VPN path. In practice, when a device connects to a VPN, you want DNS queries to be resolved using DNS servers reached through the VPN tunnel. If some lookups still reach resolvers outside that tunnel—because of configuration, network routing, or how the device handles DNS—then the device can reveal which domains you’re trying to reach.

A user diagnosing or configuring a VPN connection should therefore think in terms of operating conditions: where DNS queries go, which resolver is used, and whether network traffic routes them through the VPN.

How it works (concepts and operating conditions)

  1. Name resolution flow: When you visit a website, your device must resolve a domain name to an IP address. That resolution typically goes to a configured DNS resolver (often provided by the network, router, or VPN client).
  2. VPN tunnel expectations: With a correctly configured VPN, the expectation is that DNS queries are directed to resolvers reachable through the VPN tunnel, so the observable DNS traffic corresponds to what the VPN endpoint can handle.
  3. Where leaks come from: DNS leaks often occur when DNS queries are generated outside the tunneled path or when the device continues using an external resolver (for example, one learned from the local network) instead of using the VPN’s DNS handling.
  4. Protocol and client behavior: Different operating systems and VPN client implementations can handle DNS differently. Some systems route DNS as part of general traffic; others may treat DNS resolution specially, depending on client settings.

Practical context for a VPN setup

When troubleshooting, treat DNS as a separate “path” to validate. Even if the VPN protects most traffic, a misalignment between VPN connectivity and DNS resolver selection can still leave DNS lookups going to the wrong place.

Common practical steps (conceptual and device-appropriate) include:

  • Confirm which DNS resolver(s) your device is actually using while connected. - Check whether DNS queries follow the same interface/path as the VPN connection.