A VPN kill switch is a control intended to block traffic when the required VPN connection is unavailable. Its exact scope depends on the app and operating system.
Read what the setting promises
A control that reacts to an unexpected tunnel drop may behave differently from one that blocks all internet access until the VPN connects. Startup, manual disconnection, sleep and network switching are separate cases.
Before relying on it, find the provider’s documentation for your device. Do not infer Windows behavior from an Android screenshot or a browser-extension setting.
Test without sensitive activity
Close private work before deliberately interrupting a connection. On a device you control, use an ordinary test page and follow the provider’s test instructions. Observe whether requests stop during the specific event you are investigating, then verify that normal access returns through the intended route.
Avoid treating a page already displayed on screen as evidence of continued internet access. It may be cached. A fresh request or a controlled connection check is more informative.
Know what it does not establish
A kill switch is not an antivirus scan, and its name does not prove protection against every DNS or IPv6 leak. It also does not explain a separate bandwidth-sharing process. Check each feature’s documented behavior independently.
The source below describes Proton’s implementation. Zenshield feature availability must be confirmed in its current app and support documentation. If internet access stays blocked unexpectedly, use connection troubleshooting rather than deleting network settings at random.