The ProPrivacy Leak Test Tool
When using a VPN service it should be impossible for any website you visit to identify you by your real unique internet address (IP address). All a website (or any other internet resource) should be able to see is the IP address of the VPN server you are connected to.
If for any reason a website can see your real IP address when using a VPN then you have an IP leak. Our IP leak tool tests for all known types of IP leak.
What is IPv4?
Every internet connection is assigned a numerical IP address that computers use to uniquely identify it. The IPv4 system has been used for this since the early days of the internet, and IPv4 addresses remain by far the most common type of internet address.
One day, IPv6 addresses (see below) will completely replace IPv4 addresses, but until the new standard is much better supported, even connections with an IPv6 address are also assigned an IPv4 address for compatibility reasons.
What is an IPv4 leak?
This means a website can see your real IPv4 address, and isn't really a “leak” as such. It means your VPN is not enabled or is not simply not working at all.
What is IPv6?
IPv4 addresses are running out. Fast. The new IPv6 standard fixes the issue by using addresses much longer, thereby providing an awful lot more of them (around 340 billion billion billion billion!).
Unfortunately, although essential to the future growth of the internet, adoption of IPv6 at all levels has been slow. The result is most internet services and Operating Systems now operate a dual-stack approach, where (when IPv6 connectivity is available at all) internet traffic is sent over both an IPv4 interface and an IPv6 interface.
What is an IPv6 leak?
An IPv6 leak occurs when your IPv4 connection is correctly routed through the VPN interface, but your IPv6 connection is routed via your ISP as normal.
This means that websites can’t see your real IPv4 address, but they can see your real IPv6 address. IPv6 leaks can only occur if your device has IPv6 connectivity.
Our test ensures IPv6 connections are either being routed through the VPN interface, or that IPv6 connections are blocked in order to prevent connections outside the VPN interface.
What is a WebRTC leak?
WebRTC is an HTM5-based platform that allows high quality voice and video communication inside all modern browser windows.
In order to achieve seamless browser-to-browser communication through obstacles such as firewalls, WebRTC broadcasts your real IP address(es) to STUN servers, which keep a list of both users’ public IP addresses and their real IP addresses.
This has the unfortunate side-effect of allowing websites to bypass your VPN and find out your real IP address(es) by simply making a WebRTC STUN request.
Although primarily a browser issue, many VPN services can heavily mitigate against (but entirely fix) this problem. Our test checks for both IPv4 and IPv6 WebRTC leaks.
What is a DNS address?
The Dynamic Name System (DNS) is used to translate the easy-to-understand and remember web addresses that we are familiar with (URLs), to their “true” numerical IP addresses.
Your DNS address is the IP address of the DNS server which performs this translation, which in the normal course of things belongs to your ISP.
It is not unique to you, but your ISP can use your DNS queries to track which websites you visit, and websites you visit can contact your ISP to find out which of their users visited their website at a specified time.
What is a DNS leak?
When using a VPN, DNS queries should be sent through the VPN interface to be handled by the VPN provider - instead of your ISP. Most VPN services run their own DNS servers, but some proxy the queries to third party providers. This is fine, since the third party DNS provider doesn’t know who made the request.
A DNS leak occurs when a DNS query is sent outside the VPN interface, and is therefore handled by your ISP instead of the VPN provider. This can happen for a number of reasons, but a good VPN client should prevent it.
Our test checks for both IPv4 and IPv6 DNS leaks.
Help! I have an IP leak! What should I do now?
If our test detects that you have an IP leak, don’t panic! Please consult our Complete Guide to IP Leak Protection for a solution (the simplest always being to just switch to a VPN that doesn’t leak!).