What a VPN Kill Switch Does
Understand connection-drop protection, persistent blocking, platform differences, and what to check in your VPN app’s settings.
A VPN kill switch is intended to block traffic when the protected connection is unavailable. The exact conditions depend on the app, operating system, and setting you choose.
Read when blocking begins and ends
Some controls respond when an active VPN tunnel drops. Others can keep the network blocked before you connect or after you deliberately disconnect. Those differences affect everyday use as well as protection.
Check whether the control blocks all traffic, selected apps, or only traffic covered by the VPN. Split tunneling can intentionally send excluded traffic outside the tunnel, so read how the two settings interact.
Check each platform separately
An app feature on Windows may be absent or work differently on iPhone. IVPN, for example, documents platform-specific firewall and iOS limitations. Do not infer iPhone behavior from a desktop firewall description.
NordVPN also documents differences between its platform-specific kill-switch controls. The relevant detail is the control available in your installed app and version, rather than whether the provider has a general kill-switch marketing page.
Test ordinary situations before you depend on it
Use non-sensitive activity while learning the control. Try a Wi-Fi change, sleep and wake, and a temporary connection interruption. Confirm that the app reconnects and that you know how to restore connectivity if blocking remains enabled.
Seeing a “connected” label or failing to load one page is not a complete leak test. IPv4, IPv6, and DNS need separate checks under recorded conditions. Our testing method explains the records required before we publish a result.
A settings checklist
- Find the kill-switch or firewall control in the correct app.
- Read whether it is enabled by default and which protocol it requires.
- Check behavior before connection, after a drop, and after deliberate disconnect.
- Review split-tunnel exclusions.
- Learn the recovery steps before traveling or changing networks.
The Windows directory and iPhone directory lead to product-specific documentation. We have not published hands-on kill-switch findings yet, so feature descriptions should be read as documented support rather than independently verified behavior.