13Tem
How does a website know the DNS server a client uses?
There are websites which claim to do "DNS leak tests". I don't care so much about DNS leaks but am curious, how does the website know which DNS server I am using? I guessed it would be a header sent in the HTTP request but wasn't able to find it.
Example website: https://www.dnsleaktest.com/
EDIT: there are plenty of other examples found through a google search.
