VPN connections drop. You walk out of Wi-Fi range, the phone hops to mobile data, a server restarts, or a hotel network hiccups. For a few seconds, your device may quietly send traffic outside the tunnel. A kill switch exists to stop that.
What a kill switch does
A kill switch watches the VPN connection. If the tunnel goes down, it blocks internet traffic until the VPN reconnects. Nothing leaves your device unencrypted in the gap.
Without one, the moment the VPN drops, apps carry on using the normal connection. The Wi-Fi owner or your ISP can see what your device connects to during those seconds, and websites may see your real IP address.
When drops happen
- Switching networks: moving from Wi-Fi to mobile data, or between access points.
- Weak signal: trains, lifts, the edge of a café's Wi-Fi range.
- Sleep and battery saving: the phone pauses background apps, including the VPN.
- Server maintenance: a VPN server restarts or becomes overloaded.
- Restrictive networks: a network that blocks VPNs can cut the connection mid-session.
Do you need one?
Yes, if:
- you use public Wi-Fi regularly;
- you rely on the VPN for privacy from your ISP and do not want occasional leaks;
- your IP address showing up even briefly would be a problem.
Less important if:
- you use the VPN mainly for convenience, for example to use a home-country server while travelling, and a brief drop does not matter.
The trade-off
A kill switch means that when the VPN is down, your internet is down too. On an unstable network that can feel like "the internet keeps cutting out". That is the kill switch doing its job, but if it gets in the way you can switch it off for that session.
How to turn it on
Android
Android has a system-level kill switch that works with any VPN app:
- Settings, Network & internet, VPN.
- Tap the gear icon next to your VPN.
- Enable Always-on VPN and Block connections without VPN.
Because this is enforced by Android itself, it is reliable even if the VPN app is closed in the background.
iPhone
iOS does not offer a universal "block without VPN" toggle to regular apps. Many VPN apps provide Connect on demand or their own kill-switch option in the app settings, which reconnects automatically and limits traffic outside the tunnel. Check your VPN's settings.
Windows and macOS
Most desktop VPN apps include a kill switch in their settings. It is usually off by default; turn it on if privacy is the reason you use a VPN.
Kill switch vs Always-on
They are related but different:
- Always-on keeps trying to keep the VPN connected and reconnects after drops and reboots.
- Kill switch blocks traffic while it is not connected.
Using both gives you a VPN that is connected almost all the time, and safe in the moments it is not.
Other leaks a kill switch will not catch
A kill switch protects against drops. It does not fix:
- DNS leaks, where DNS lookups go to your ISP even while the VPN is on;
- WebRTC leaks, where your browser reveals your real IP through video-call technology;
- IPv6 leaks, where IPv6 traffic bypasses an IPv4-only tunnel.
Run a leak test after setting up any VPN. Korp VPN has DNS and WebRTC leak tests built into the app.
The bottom line
If you use a VPN for privacy, turn on a kill switch, or Android's "Block connections without VPN", and run a leak test once. It takes a minute and closes the most common gap.
Korp VPN offers unlimited data, a strict no-logs policy on RAM-only servers, a stealth protocol for networks that block VPNs and built-in leak tests. Plans are $4.99 for three months or $17.99 a year.