A VPN kill switch is a security feature that automatically blocks a device's internet access if its connection to the VPN server drops, preventing the user's real IP address, DNS queries or browsing activity from being briefly exposed. This matters because a VPN only protects privacy while it is actively connected; without a kill switch, momentary drop-outs can silently undo that protection, so the feature turns a VPN into a more reliable "set and forget" privacy tool rather than one requiring constant manual monitoring.

Kill switches typically work at either the application level, blocking only selected apps, or the system level, cutting off all internet traffic until the VPN tunnel is restored, with system-wide switches offering stronger but sometimes more disruptive protection. Most leading VPN services include the feature, though free or budget providers may not, and it is usually found in app settings under labels such as "network lock," "leak protection" or "block connections if disconnected." Users are advised to enable it for sensitive apps like email or browsers, make exceptions for time-critical tools such as video calls or gaming, and pair it with an auto-connect feature for continuous protection.