Direct answer

When you use a VPN on public Wi‑Fi, your setup “decisions” mainly come down to (1) how the VPN connection is established on your specific device, (2) which network details it can safely use (Wi‑Fi, DNS, and routing), and (3) how you confirm it’s actually connected and behaving as expected. Use the VPN first to reach normal destinations, then diagnose any issues (DNS failures, captive portals, blocked traffic) with simple checks.

How it works (setup and decisions)

A VPN creates a protected communication path between your device and the VPN endpoint. On public Wi‑Fi, your device still needs ordinary connectivity to reach the VPN endpoint (for example, passing the Wi‑Fi’s network rules and any login page). Then, the VPN client decides how to handle traffic—typically which network interface to use, whether to route all traffic through the VPN, and how name resolution (DNS) is performed.

Your practical workflow is: connect to the Wi‑Fi, ensure the VPN client can start and stay connected, then confirm that common signs match your expectations (connection status, no unexpected DNS leakage symptoms, and normal access to sites that previously failed).

Practical context on public Wi‑Fi

Public Wi‑Fi often includes captive portals, restrictive firewalls, and inconsistent routing. These can prevent the VPN from connecting at all, or allow it to connect but break access to specific services. If you’re diagnosing, try to identify which step fails: Wi‑Fi association, VPN handshake/connection, DNS resolution, or application access. If you’re configuring, align settings with your device’s VPN client options (for example, “connect on startup” and “route all traffic”) and keep one change at a time so you can tell what fixed or caused the problem.

Limitations to keep in mind

A VPN does not guarantee anonymity, safety, or access. Performance and availability vary by network, device, location, provider, and time. Also, VPN behavior can change with different networks or Wi‑Fi types, so any “works everywhere” assumption is unreliable. Current product capabilities and legal or empirical claims would require up‑to‑date verification.