What a Kill Switch Does
When your VPN connection drops unexpectedly, your device defaults to your regular internet connection. For a few seconds or longer, your traffic is unprotected and your real IP address is visible. A kill switch prevents this by cutting your internet connection entirely the moment the VPN tunnel goes down. No VPN, no internet. This sounds drastic but is essential for any use case where exposure of your real IP would be a problem.
Who Actually Needs a Kill Switch
If you use a VPN primarily for accessing geo-restricted streaming, a kill switch is convenient but not critical. If your VPN drops, Netflix shows your real location for a moment. Annoying, but not a privacy violation. For journalists, activists, or anyone connecting from a location where being identified could be dangerous, a kill switch is a hard requirement. It is also important for torrent users who want to ensure their real IP is never exposed to peer-to-peer networks.
System-Level vs App-Level Kill Switch
App-level kill switches cut internet only when the specific VPN application loses connection. System-level kill switches operate at the operating system level and can cut all traffic regardless of which app drops. System-level is more reliable because it catches edge cases where the app closes unexpectedly or crashes rather than gracefully disconnecting. Look for providers that offer both options.
Which Providers Include Kill Switches
Mullvad, NordVPN, and ExpressVPN all include configurable kill switches in their desktop and mobile clients. ProtonVPN includes a permanent kill switch option that keeps internet blocked until you explicitly re-enable it. For mobile, iOS has historically been more difficult to implement kill switches on due to Apple restrictions, though most major providers have found workarounds via always-on VPN configuration profiles.
How to Check if Yours Is Working
Enable the kill switch, connect to VPN, then manually disconnect the VPN from within the app rather than disabling the kill switch first. Your internet should stop working. If you can still browse, the kill switch is not functioning. Run this test on both desktop and mobile.