The Gap in Most VPN Setups
A VPN protects you only while the tunnel is up. If the connection drops for two seconds on an airport network, apps quietly fall back to the raw connection and your traffic goes out unprotected. A kill switch closes that gap by blocking traffic the moment the tunnel fails.
How a Kill Switch Works
When active, the kill switch monitors the tunnel state. On a drop, it either refuses to route any non-tunnel traffic or closes the interfaces that would leak data. Good implementations trigger in milliseconds, before an app can open a new unprotected socket.
Where to Find It
Desktop clients from serious providers expose a kill switch toggle in the settings, often with two modes: app-level (protects only listed apps) and system-level (blocks everything until the tunnel returns). System-level is the stronger choice for travel because you rarely know in advance which app will try to phone home.
Mobile Kill Switches
On iOS and Android the situation is different. iOS has no universal third-party kill switch, so the protection comes from the on-demand rules and the provider’s own network extension. Android apps can implement a per-app or VPN-only mode that stops traffic when the tunnel drops. Read the provider’s docs rather than assuming a toggle exists.
How to Test Yours in 60 Seconds
- Connect to a server and confirm your public IP has changed.
- Enable the kill switch.
- Disable the tunnel abruptly (toggle the VPN off, then kill the process, or put the device in airplane mode briefly).
- Without reconnecting, open a browser and check your IP again.
- If the page loads with your real IP, the kill switch failed. If nothing loads, it worked.
Run this test before every trip. A kill switch that has never been verified is a feature you are only hoping works.
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