http://airvpn3epnw2fnsbx5x2ppzjs6vxtdarldas7wjyqvhscj7x43fxylqd.onion/tags/ipleak.net
It's generally used to check if there are leaks (IP, DNS, RTC etc.) with a connection to a VPN, Tor, proxy etc.
We developed it with updated state-of-the-art techniques to detect leaks.
The main page performs around 30 DNS detection tests to build a list.