Many people use a VPN believing it makes them invisible online. But VPNs can leak your real identity in at least five different ways — and most users never check for any of them.
Leak 1: WebRTC IP Leak
WebRTC is a browser technology for real-time communication that can reveal your real IP address even when connected to a VPN, because WebRTC connections bypass VPN tunnels. Affects Chrome, Firefox, and Edge users. Test with the Anonymiz WebRTC Leak Test. Fix by disabling WebRTC in Firefox via about:config, or using a WebRTC control extension in Chrome.
Leak 2: DNS Leak
If DNS queries go through your ISP servers instead of your VPN, your ISP can see every site you visit. Test with the Anonymiz DNS Leak Test. Fix by using a VPN with DNS leak protection or enabling DNS over HTTPS in your browser.
Leak 3: Real IP on VPN Drop
If your VPN connection drops briefly, your real IP may be exposed before it reconnects. Fix by enabling the kill switch in your VPN app, which blocks all internet traffic when the VPN disconnects.
Leak 4: IPv6 Leak
Most VPNs only tunnel IPv4 traffic. If your ISP assigned you an IPv6 address and the site supports IPv6, your real IPv6 may be sent directly. Test with the Anonymiz IP Checker, which shows both IPv4 and IPv6. Fix by choosing a VPN that explicitly tunnels IPv6.
Leak 5: Browser Fingerprint
Even with a masked IP, websites can track you through browser fingerprinting — your screen resolution, fonts, timezone, and plugins create a unique identifier. Test with the Anonymiz Browser Fingerprint Tool. Fix by using Brave or Firefox with privacy extensions.
Run All Tests at Once
Use the Anonymiz Browser Privacy Score — it runs 12 checks and scores your overall privacy level in one test.
How Often Should You Test?
Test whenever something changes: a new version of your VPN app, a browser update, a new network such as hotel or office Wi-Fi, or a change to your VPN settings. Leaks often appear after an update quietly resets a setting you had changed.
Reading Your Results Correctly
- DNS servers you do not recognise are not always a leak, because many VPNs use third-party DNS infrastructure. It is a leak if the servers belong to your internet provider.
- A local address such as 192.168.x.x in a WebRTC test is normal. The problem is your public IP address appearing.
- Your IPv6 address showing while your IPv4 address is hidden means the VPN is not handling IPv6 traffic.
What a VPN Cannot Hide
Even with every leak fixed, a VPN does not stop websites recognising you when you log in, through cookies already stored in your browser, or from details you type into forms. Pair it with a privacy-focused browser, and use separate browser profiles for accounts you do not want linked together.
