Direct answer

Setup and user decisions matter because DNS leaks are about where DNS queries are actually resolved while you expect the VPN to be handling traffic. When diagnosing, you focus on whether your device keeps using only the VPN-provided DNS path, or whether it sometimes falls back to the local network’s DNS (or another resolver) during connection setup, routing changes, or app-specific behavior.

How it works (operating conditions)

When you connect a VPN, two things need to line up: (1) your device must route DNS queries through the VPN’s expected path, and (2) DNS resolution must not be diverted by settings, browser/app behavior, or network features.

In practice, “setup and decisions” usually includes:

  • Choosing connection settings that define how DNS is handled (for example, whether DNS is directed through the tunnel or left to the local network).
  • Timing of tests: DNS behavior can differ during initial connect, reconnects, sleep/wake, or IP changes.
  • Device behavior: some operating systems and apps cache DNS, use local resolvers, or have their own DNS preferences.

Practical context: comparing what to check

A useful way to think about diagnostics is to compare expected vs observed behavior during the same “VPN on” window.

Look for signs that DNS is or is not taking the intended route:

  • Re-run tests after the VPN is fully connected, not only while it is negotiating.
  • Clear DNS caches (or account for caching) so you observe fresh resolutions.
  • Test multiple domains and, if possible, confirm using at least two independent verification methods.

If results are inconsistent, treat it as a configuration or environment question rather than a single yes/no outcome: changing network (Wi‑Fi vs mobile), location, firewall rules, or device settings can alter DNS resolution behavior.

Limitations you should account for

A VPN does not guarantee anonymity, safety, or access. Performance and availability vary by network, device, location, provider, and time. Also, DNS-leak diagnostic tools can have false positives/negatives depending on how they measure DNS visibility and how the device routes or caches queries.