Direct answer

Setup and decisions around kill switches are useful when you have a defined requirement: if the VPN drops, you want the most relevant traffic to stop rather than continue on an unprotected path. This is practical for remote professionals and small-business teams handling internal systems, private documents, or access that must not silently degrade when the connection is unreliable.

The limit is equally important: a kill switch cannot guarantee anonymity, safety, or reliable access. Outcomes depend on the device, operating system, network type (home Wi‑Fi, mobile hotspot, corporate LAN), and how your apps use DNS and network connections.

What it means in plain terms

A kill switch is designed to change behavior during a VPN failure. Instead of letting all network traffic continue normally, it aims to restrict traffic so that you don’t unintentionally send data over non‑VPN routes.

In practice, it’s a traffic-control decision that you set ahead of time—so it triggers when the VPN state changes unexpectedly (for example, Wi‑Fi drops, a laptop sleeps and resumes, or the VPN service restarts).

How it works in a practical model

Think of it as two phases:

  1. Normal operation: the VPN is connected, and your chosen traffic flows through it.
  2. Failure mode: the VPN is disconnected or unreachable, and the system applies your kill-switch policy.

Setup becomes useful when you align the policy with real workflows—for example, whether your critical apps should block general internet access, allow limited updates, or restrict only certain destinations.

Parts of the decision (what you should configure)

Focus on the choices that affect whether the “failure mode” matches your threat model:

  • Scope of blocking: what types of traffic are restricted (all traffic versus specific categories).
  • DNS handling: whether DNS requests follow the VPN path or get blocked during failure.
  • Device behavior: how the kill switch behaves on sleep/wake, roaming between networks, and app restarts.
  • Reconnection behavior: what happens when the VPN returns—does traffic remain blocked until the tunnel is fully ready?