Ask HN: Are there URLs without domain extensions (like .com or .in)

From a network/protocol point of view, there's nothing really special about the top-level domains (TLDs), other than what we call the "internet" is largely based on names allocated by Internet Corporation for Assigned Names and Numbers (ICANN) [1]. They're just domains, and though we call them subdomain.domain.tld, the relation of "subdomain" to "domain" is the same as that of "domain" to "tld".

The only TLD I could find that has an A record is `.ai`, and it doesn't seem to work anyway. Apparently, doing that can cause compatibility problems, which is partly why it's uncommon, and ICANN rules have prohibited doing so for any of the newer generic TLD's they've assigned [2].

If you run your own DNS, you can have any top-level domain you want, and can put A records on it. If you can get other people using them (eg: changing their DNS servers to point at yours), you can even offer "domain registrations" as well as basically control their internet experience (want google.com resolve to your own your site? no problem!). In fact, there are several alternative DNS roots [3] that have done exactly this.

Microsoft actually did have a whole system for this at one point, which worked in IE and was called RealNames [4], but was shut down in 2002.

[1] https://en.wikipedia.org/wiki/ICANN

[2] https://stackoverflow.com/questions/40349412/why-do-not-more...

[3] https://en.wikipedia.org/wiki/Alternative_DNS_root

[4] https://en.wikipedia.org/wiki/RealNames

Here is a URL without any domain extension:

http://3520653040/

There are data: urls. But there are no domains without a top level domain or top level domains with A records(resolve to IP)