Comment by noAnswer
4 hours ago
DNS servers can take the IP address of the client into account. If you query a record for amazon.com from the USA you will get a different answer than from Europe. (And you don't need anycast for that.)
That the client information doesn't get lost when it goes through different resolvers the DNS extension EDNS Client Subnet (ECS) was invented.
https://en.wikipedia.org/wiki/EDNS_Client_Subnet
explains it better than me. The whole point of the extension is to make geo-guessing the original client over DNS more stable.
Now you can have privacy conscious DNS servers that strip the ECS information (or mess with it somehow) and instead of the server closest to you you get the global fallback for example. (controld.com goes as far to say "switch countries without a VPN" by only messing with ECS. No idea how stable that is though.)
Interesting! I always just assumed sites used geoDNS to figure out where the user is. I like the "Controversy over lack of support" section in the wikipage. I've been mainly using NextDNS and learned that they anonymized this information https://medium.com/nextdns/how-we-made-dns-both-fast-and-pri...