What is an IP Address and How Does a VPN Change It?
An IP address is a unique numerical identifier assigned to every device connected to the internet. A VPN replaces your real IP address with the VPN server's IP address, masking your location and identity online.
An IP address (Internet Protocol address) is a unique numerical label assigned to every device that connects to the internet. Think of it as your device's mailing address on the internet — it tells other servers where to send responses, and it reveals information about your geographic location and internet service provider to every site you visit.
IP addresses come in two formats:
- IPv4 — Four sets of numbers separated by dots (e.g., 192.168.1.1) — the traditional format
- IPv6 — Eight groups of hexadecimal values separated by colons — designed to replace IPv4 as available addresses run out
What Your IP Address Reveals
Every website, app, and online service you connect to logs your IP address by default. From your IP address, they can typically determine:
- Your country and approximate region (city-level in many cases)
- Your ISP
- Whether you're using a VPN server IP (these are often identifiable from public IP reputation databases)
- Your general connection type
Advertisers use IP addresses for targeting. Law enforcement uses them in investigations. Geo-blocking systems use them to restrict content. Data brokers aggregate activity across IPs to build profiles.
How a VPN Changes Your IP Address
When you connect to a VPN, your traffic is routed through a VPN server. To every website and service you reach, your traffic appears to originate from the VPN server's IP address — not your own. Your real IP remains hidden behind the VPN server.
The process:
- Your device sends traffic encrypted to the VPN server
- The server decrypts it, makes the request on your behalf
- The destination sees the VPN server's IP
- The response returns to the VPN server, which encrypts and forwards it to you
Your ISP can see your device's IP and the VPN server's IP, but not what traffic you're exchanging.
Static vs. Dynamic VPN IPs
Most VPN servers use dynamic shared IPs — your exit IP changes each session, and hundreds of users share the same IP pool. This adds privacy through obscurity (many users, one IP) but can trigger CAPTCHAs and blocks on some services.
A dedicated IP gives you a fixed IP assigned only to your account — more consistency, but less anonymity.
IPv6 and VPN Leaks
IPv6 introduces a common vulnerability: some VPN clients only tunnel IPv4 traffic. If your ISP assigns you an IPv6 address and the VPN doesn't handle it, IPv6 traffic bypasses the tunnel entirely — exposing your real IPv6 address. This is a specific type of IP leak that goes beyond DNS.
Check that your VPN client explicitly handles IPv6 — either tunneling it or disabling it on the system when connected. Mullvad and ProtonVPN are among the providers that handle IPv6 leaks correctly by default.
IP Addresses and the Kill Switch
The kill switch is specifically designed to prevent your real IP from being exposed if the VPN connection drops. Without a kill switch, a momentary VPN disconnect causes your device to revert to your real IP — which websites log immediately. A kill switch cuts all traffic in that gap.