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Think of a VPN kill switch as an emergency brake for your internet connection, instantly cutting off traffic if your VPN disconnects. The whole point of using a VPN is to keep your data encrypted and private, and safe from prying eyes. Without a kill switch, if your VPN connection drops, even momentarily, your data may be exposed to your ISP, IT administrators, or worse, advertisers. Even top-tier VPNs can experience unexpected disruptions, so it's an essential part of your protection. With that in mind, I'm here to explain what a kill switch is, how it works, and why you should always have it enabled.
This article was made possible in part by Proton VPN. It was written and edited independently without partner oversight.
How a Kill Switch Protects Your Data
Picture your computer as a node receiving the internet from a router in the form of a data stream. That data stream then flows out an exit gate and is sent into the sea of data at large, to the servers for the sites you visit and the applications you use. I go over how a VPN connection works in detail here, but, in short, connecting to a VPN replaces your data stream’s regular exit gate with an extra security checkpoint where your data is scrambled and anonymized through a process called encryption.
A kill switch monitors that security checkpoint. If your connection to that checkpoint is disrupted, then the kill switch slams the exit and entry gates shut before any data can escape. This action prevents your computer from receiving an internet connection until the protection of your VPN is restored. A kill switch is important because even a momentary leak can compromise your activities to your ISP and third-party advertisers.
VPN disruptions are common and can occur for any number of reasons, including:
- The Wi-Fi network you’re connected to may be unstable.
- Your PC restarts overnight and connects to the internet automatically without switching on your VPN.
- Your device accidentally disconnects from your VPN service due to connectivity issues.
- You switch VPN servers.
If any of these scenarios occur and are detected by a VPN’s kill switch, your internet connection will be interrupted to prevent your data from being transmitted without encryption and possibly leaking out to unintended destinations.
Types of VPN Kill Switches: Application vs. System
All kill switches have the same purpose: to terminate your internet connection. However, the effect a kill switch has can vary. Application-level and system-level kill switches are the two main varieties you’ll see in a VPN app.
Application-Level Kill Switches
An application-level kill switch is less secure than its system-level counterpart because it only affects the apps you select. For example, you could configure an application-level kill switch to prevent BitTorrent from sending data out if your VPN connection falters, without affecting your other active applications. It’s best to use this type of kill switch with caution, since it's easy to miss an app or misconfigure the switch in a way that leaks your data.
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System-Level Kill Switches
A system-level kill switch doesn’t pick and choose what it shuts down. Rather, this kill switch halts all data going in and out of your system until the VPN connection is restored. System-level switches are much more secure but can affect downloads or other ongoing processes when triggered. It’s worth noting that split tunneling will not bypass a system-level kill switch, since all data will be halted regardless of whether it is routed through your VPN’s encryption.
Both types of kill switches can be configured for automatic or manual operation. A manual kill switch needs to be toggled on whenever you need it, while an automatic one stays on when the VPN app is running. Most of the top VPNs come with kill switches set to automatic by default. Even so, I recommend checking your settings and double-checking if it is enabled before engaging in any sensitive tasks.
Step-by-Step: How to Enable a VPN Kill Switch
Enabling a kill switch is as simple as navigating to a VPN’s settings and switching it on. For system-level switches, you’re already done!
(Credit: PCMag/Proton VPN)Application-level kill switches require a bit more fine-tuning, since you have to go through and select every app you want protected. While many VPNs now have the kill switch enabled by default, you should definitely check whether it's running and turn it on if it isn't.
The Privacy Benefits of Always Using a Kill Switch
If you’re privacy-conscious enough to be using a VPN, then you shouldn’t take an unnecessary risk by forgoing a kill switch. Using one doesn’t impact your performance, either. During testing, I evaluate a VPN’s performance and have never experienced a slowdown when a kill switch is enabled. Check out the chart below showcasing the fastest VPNs if performance is a primary concern:
You can benefit from a kill switch regardless of what you’re doing on the network. It’s a feature that I consider a fundamental must-have from any service. It’s doubly important to enable a kill switch if you’re engaging in sensitive activities, such as torrenting or traveling to a country with surveillance laws. If your IP address becomes even temporarily visible to the outside world in those instances, your ISP or government could use it to identify and, in some cases, issue a citation or warning.
Thankfully, most of the VPNs we've reviewed include a kill switch feature when you use either a desktop or mobile client. Only a few work on specific router-level VPN installations, however, which is a disadvantage of this kind of VPN setup. We note which ones do in each of our reviews.
Beyond Kill Switches: Building a Complete Online Security Setup
Even with a kill switch, a VPN only secures your outgoing browsing data. A VPN can’t prevent you from other online dangers such as malware, doxxing, and data breaches. I recommend making a VPN just one part of a larger online security and privacy toolkit. Pairing a VPN with a strong antivirus, password manager, and using multi-factor authentication will greatly strengthen your online security compared with a VPN on its own.