SSysLeak

Guide

What Is a VPN? A Plain-English Guide to How They Work

A VPN — Virtual Private Network — routes your internet traffic through an encrypted tunnel to a server run by the VPN provider. To every website you visit, your connection then appears to come from that server instead of from your home or phone. That single redirection is the whole idea, and it's also the source of most of the confusion about what a VPN can and can't do.

This guide explains, in plain terms, what actually changes when you turn a VPN on — and, just as important, what doesn't.

What a VPN actually hides

When the tunnel is up, two things change for the sites you visit:

  • Your IP address. Sites see the VPN server's IP, not yours. Your real public IP address — and the rough location and ISP tied to it — stays hidden from them.
  • Your traffic from your network. Your ISP (and anyone on the same Wi-Fi) can see that you're connected to a VPN, but not which specific sites you load or what's in the pages.

That's genuinely useful. On public Wi-Fi it stops the coffee shop network from snooping on your traffic, and it stops websites from reading your location straight off your IP.

What a VPN does not hide

This is where expectations and reality split. A VPN does not make you anonymous. Several things still identify you:

  • Browser fingerprinting. Your browser leaks a surprising amount on its own — screen size, fonts, graphics hardware, time zone and more — which combine into a browser fingerprint that follows you across IP changes. Switching IPs doesn't change your fingerprint.
  • Logins and cookies. If you sign into an account, you've identified yourself regardless of which IP you came from.
  • WebRTC leaks. A feature built into browsers for video calls can reveal your real IP address even while the VPN is on, unless it's blocked.

That last one matters most, because it silently defeats the main thing you turned the VPN on for.

How VPNs leak — and how you'd know

Two common "tells" give away VPN users, or undo the protection entirely:

  1. WebRTC leaks. The browser surfaces IP addresses that ordinary page loads never would. You can confirm whether yours does with the WebRTC leak test.
  2. Time-zone mismatch. Your VPN exit is in one country, but your browser clock still says another. Any site can compare the two and conclude you're on a VPN.

Neither requires special access — any website can check both from ordinary JavaScript. So "I'm on a VPN" is often more visible than people assume.

Do you actually need one?

A VPN is the right tool for a specific job: hiding your IP and encrypting your traffic on untrusted networks. It is not a privacy cure-all, and pairing it with a uniquely identifiable browser fingerprint can even make you easier to single out, not harder.

The honest answer is to measure your own setup rather than trust the marketing. See exactly which signals your connection gives away — VPN tells included — below.