What Is VPN Kill Switch?
A VPN kill switch is a safety feature that immediately blocks your device's internet traffic if the VPN connection drops unexpectedly. Without it, your device silently falls back to the unprotected connection — exposing your real IP address and unencrypted traffic until the VPN reconnects. With a kill switch active, nothing leaves your device except through the encrypted tunnel.
Why VPN connections drop — and what leaks when they do
VPN tunnels drop for ordinary reasons: switching between WiFi and cellular, weak signal, sleeping and waking a laptop, server maintenance, or aggressive network filtering. Each drop creates a gap of seconds to minutes where, without a kill switch, apps keep transmitting over the raw connection.
What leaks in that gap: your real IP address (to every site and app with an open connection), DNS queries (to your ISP), and any unencrypted traffic. For everyday browsing this is a privacy regression; for anyone relying on a VPN in a restrictive country or while handling sensitive work, it is the failure that matters most.
App-level vs system-level kill switches
An app-level (or 'soft') kill switch is implemented by the VPN application: it watches the tunnel and shuts off traffic, or specific apps, when the tunnel fails. It works well but depends on the VPN app itself running correctly.
A system-level (or 'hard') kill switch is enforced by the operating system's firewall or network stack: traffic is only permitted through the VPN interface, period. If the tunnel dies — or even if the VPN app crashes — nothing can route around it. On iOS, the equivalent is 'Always-On VPN' via Connect On Demand; on Android, the OS-native 'Block connections without VPN' setting; on desktop, firewall-based modes that top providers implement.
When you actually need it
Always-on for: torrenting (an IP leak defeats the purpose entirely), restrictive countries (a leak can expose VPN use itself), journalists and others with real adversaries, and any long-running session you won't be watching. Reasonable to skip for: casual streaming on your home network, where a drop is an inconvenience rather than a risk.
All eight VPNs ranked on this site ship a kill switch on desktop; mobile support varies between app-level toggles and reliance on the OS-native enforcement, which we verify in testing.
Frequently Asked Questions
Should I always keep the kill switch on?
If you use a VPN for privacy (rather than only for streaming convenience), yes — the cost is occasional blocked connectivity during reconnects, and the benefit is that the protection can't silently fail. For torrenting or use in restrictive countries it is non-negotiable.
Why is my internet blocked when the VPN disconnects?
That's the kill switch doing its job: it blocks all traffic until the tunnel is re-established. Reconnect the VPN, or turn off the kill switch if you intentionally want to browse unprotected.
Do iPhones have a kill switch?
Effectively yes — iOS's 'Connect On Demand' (Settings > General > VPN) re-establishes the tunnel automatically and prevents traffic outside it. Most top VPN apps configure this when you enable their always-on option.
Does a kill switch slow down my connection?
No. It's a routing/firewall rule, not traffic processing — it has zero impact on speed while the tunnel is up.