Direct answer
When diagnosing or configuring a VPN connection, it helps to treat a kill switch as a safety control with boundaries, not a guarantee. The main risks and limitations are that it may only apply to certain apps or interfaces, it can behave differently depending on operating system and client behavior, and it cannot compensate for every failure mode. A VPN also does not guarantee anonymity, safety, or access—especially when setup decisions are incorrect or when the network environment changes.
How a kill switch works (and where it can fall short)
A kill switch is designed to prevent internet traffic from continuing when the VPN connection is lost or not established. In practice, “preventing traffic” depends on operating conditions such as the VPN client’s ability to detect disconnects, the scope of protection (for example, all traffic versus selected applications), and the device’s networking stack. If the client fails to notice a drop early enough, or if traffic is sent through an unprotected route, you may still see exposure.
Common side effects include temporary loss of connectivity while the VPN reconnects, unexpected blocking of legitimate services, and behavior differences across protocols and network transitions (such as switching Wi‑Fi networks or moving between mobile coverage).
Practical context for setup and decisions
Start by mapping what you expect to be protected: the VPN client itself, all system traffic, or specific apps. If you assume broader coverage than the feature actually provides on your device, you can make a risky decision. If you need uninterrupted access for certain services, a kill switch that blocks too broadly may trigger outages.
Performance and availability also vary by network, device, location, provider choices, and time. So even when the kill switch prevents traffic during a VPN failure, the overall user experience can still degrade during reconnect events.
Limitations to keep in mind
First, a kill switch cannot remove all uncertainty about your exposure across every failure mode, because it depends on detection timing and the exact routing paths available on your device.