.tk and .ml. It doesn't get cheaper than free and .ml is a great typo squatting TLD for .nl which nobody seems to realise yet so a lot of domains are still available. Educational purposes only!!
I believe .tk and .ml are currently closed for registration after financial concerns and lawsuits about malicious domains. I'm working on a project that offers free subdomains under the condition that they are routed to private IP ranges. I believe this will reduce malicious use while still helping people use Let's Encrypt and other domain verified certificates.
A while back I noticed that .biz specifically has its own checkbox in the o365 spam controls. And sure enough I don't think I've ever done legitimate business on a .biz. I wonder what the heck happened to it.
The only .biz I've ever interacted with is Minimus.biz, and it looks like they've barely touched their site since 2006. Just the way I like it, honestly.
Sending a .biz link in an SMS will be blocked by Google, and the sender won't be informed the message was not sent. Cheap domains are cheap for spammers too.
Thanks for the suggestion, but I feel like the free domains are unreliable and have weird conditions. I also I think it's been said before some of the sites offering them are suspect: https://news.ycombinator.com/item?id=27951785
I was just thinking for personal projects & game servers, would be nice to have a bunch of cheap domains one could use.
It's still a rough MVP but it's online and working: https://www.getlocalcert.net/