What a kill switch actually does
The feature that matters most and gets explained least. It is thirty seconds of understanding.
Updated 2026-09-26
A VPN connection is not permanent. It drops when you change network, when you come out of a tunnel, when a server restarts, when your laptop wakes up. Usually for a second or two.
A kill switch decides what happens during those seconds. Without one, your device does the helpful thing and falls straight back to the ordinary connection, and everything carries on — over the network you were specifically avoiding, from your real address, with no warning.
With one, traffic is blocked until the tunnel is back. Things pause for a moment. Nothing leaks.
Why the gap matters more than it sounds
It is not the two seconds of browsing. It is what your device does automatically in those two seconds: apps reconnect, mail syncs, messaging clients re-authenticate, and anything that was watching the network gets a clean look at who you are and what you are connected to. One momentary drop on a hotel network can undo the reason you turned the VPN on.
This is also why it matters most on a phone, which changes network constantly and does it silently.
The two kinds
Application level. The VPN app notices the drop and blocks traffic. Good, and it depends on the app being alive. If the app crashes, so does the protection.
System level. Firewall rules on the device itself say traffic may only leave through the tunnel. Survives the app crashing, which is the case that matters. Worth preferring where offered.
Checking yours works
Thirty seconds, and worth doing once:
1. Connect the VPN and check your address on our IP tool. It should say you are coming through us. 2. Start something continuous — a video, a large download. 3. Force a drop: switch the VPN server, or turn Wi-Fi off and on. 4. Watch what happens. With a working kill switch the video stalls and resumes. Without one it keeps playing without a blink, which means it never stopped. 5. Reload the IP tool during the gap if you can. If it shows your real address, the kill switch is not doing anything.
The setting people miss
Many apps ship with it off, because it makes the product feel less smooth when a connection is flaky. Look for "kill switch", "network lock" or "always-on VPN" in settings and turn it on. On Android the equivalent lives in the system settings rather than the app: VPN, the gear icon, "Always-on VPN" and "Block connections without VPN".
If you only change one setting after reading anything on this site, make it that one.
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