A VPN that drops its connection for even a few seconds can expose your real IP address and browsing activity. Here's why kill switches and DNS leak protection are non-negotiable — and how to verify yours is working.
A VPN is only as private as its weakest moment. Most VPN connections are stable — but network interruptions happen. Your Wi-Fi drops for a second, your router reboots, your laptop wakes from sleep. In that brief window between your VPN disconnecting and reconnecting, your device falls back to your regular internet connection — and your real IP address, DNS queries, and unencrypted traffic are briefly exposed. For most casual users, this is a minor inconvenience. For anyone using a VPN for genuine privacy, it's a critical failure.
A kill switch solves this by monitoring your VPN connection and blocking all internet traffic the moment the VPN drops. If the VPN disconnects, the kill switch cuts your internet connection entirely — preventing any traffic from leaking over your unprotected connection. When the VPN reconnects, the kill switch releases the block and traffic flows again. The result is that your real IP address is never exposed, even during brief connection interruptions.
There are two types of kill switches: application-level kill switches (which block specific apps you designate when the VPN drops — useful if you only need VPN protection for certain activities) and system-level kill switches (which block all internet traffic on the device when the VPN drops — the stronger option for comprehensive privacy). Most top-tier VPN clients offer both. NordVPN, ExpressVPN, Mullvad, and ProtonVPN all include system-level kill switches in their desktop and mobile clients.
DNS leaks are a separate but related problem. Even with a VPN active, your device may send DNS queries outside the VPN tunnel — directly to your ISP's DNS resolver or your router — rather than routing them through the VPN. This is called a DNS leak, and it means your ISP can still see which domains you're looking up despite your VPN being connected. DNS leaks are most common on Windows, where the operating system's DNS resolution can bypass the VPN tunnel under certain conditions.
How to test for DNS leaks: visit dnsleaktest.com or ipleak.net while connected to your VPN. These sites show which DNS servers are resolving your queries. If you see your ISP's DNS servers in the results, you have a DNS leak. You should see only your VPN provider's DNS servers (or a third-party resolver your VPN routes through). If you detect a leak, check your VPN client's settings for a 'DNS leak protection' or 'private DNS' option and enable it. If the leak persists, contact your VPN provider's support.
WebRTC leaks are a third category: WebRTC is a browser technology used for video calls and peer-to-peer connections that can reveal your real IP address even when a VPN is active, because WebRTC makes direct connections that bypass the VPN tunnel. Test for WebRTC leaks at browserleaks.com/webrtc. To fix: in Firefox, set media.peerconnection.enabled to false in about:config. In Chrome, install the uBlock Origin extension (it blocks WebRTC leaks by default). Brave Browser blocks WebRTC leaks natively. Verifying all three — IP, DNS, and WebRTC — gives you confidence that your VPN is actually protecting what you think it is.
Safety 1st Editorial Team
This article is credited to Safety 1st Editorial Team. Safety 1st Consumer Protection has republished this content with attribution.