There are still some lists of free DNS servers out there.
One of the oldest (and I think best) Free and Public DNS Servers. It is my go-to list.
Some group keeps a list of public DNS servers in the USA, with pages for lists of servers in other countries. You can download them in a csv file. There are also lists for a lot of other countries. Another list is Public DNS.
Another top ten list (with reasons you might want to use some of them) is at TechWhoop.
The Arch Linux Wiki has a good list including a short analysis of different servers (archive here). They point to a page on Wikipedia.
You could also go with OpenNIC. Here is their list of public Tier 2 servers. Their anycast servers do not work for me; perhaps my broadband provider is blocking them.
If you have a hard time remembering all of this, you can fall back on 1.1.1.1 (Cloudflare), 8.8.8.8 (Google) or 9.9.9.9 (Quad9). I tried X.X.X.X for 2 through 7, and got nothing.
I was using the DNS servers from Uncensored DNS, but they seem to be offline as of 2017-09-30. As of 2023-07-23, they are not responding to dig and host requests. Perhaps my broadband provider is censoring Uncensored DNS.
On Linux, you can test a DNS server with the host command: host $DOMAIN_TO_TEST $DNS_SERVER_IP_ADDRESS:
host google.com 8.8.8.8
or you can use the dig command: dig @$DNS_IP $DOMAIN_TO_TEST
dig @91.239.100.100 google.com
Image from BNF Grec 543, a 14th-century manuscript housed at Bibliothèque nationale de France; image from BnF Gallica; allowed under public domain.
This page was created in Emacs with Org Mode and Love. You’re welcome. Stop looking at your stupid phone all the time.