[iRomain]

So they registered the domain "www" just like they could have registered "google" or "lol".

You can access Google by typing:

- google.com (domain name)

- www.google.com (subdomain)

The same for the domain in question:

- www.ai (domain name)

- www.www.ai (subdomain)

~~The reason why typing ".ai" or "ai", etc. In your browser works is in IMO due to the internals of the browser that automatically adds a www in front of the domain if it can't resolve it because historically so many websites run on http://www.example.com and neglect to setup http://example.com~~

Edit: as pointed by another comment (https://news.ycombinator.com/item?id=31690379) there are actually TLDs with A records which is the case here.

So to take my example from above: The registry responsible for the AI TLD set up a website on the domain name "www.ai" but neglected to set it up on the subdomain "www.www.ai" Instead, they set it up on the TLD "ai" which is indeed very unusual.

[LeoPanthera]

This is not correct. The TLD alone is a valid domain name, although in most cases it must be followed by a trailing dot. "ai." is valid, "ai" may not be.

[iRomain]

It is a valid domain in the technical DNS sense. But practically speaking, each TLD has "ns" entries in the root zone database, not "A", "CNAME", etc. entries. This is just a guy who registered www under a TLD that's it.

[LeoPanthera]

This has nothing to do with the "www" subdomain. I assure you that the unix "host" tool is not trying to guess subdomains if the lookup fails:

  $ host "ai."
  ai has address 209.59.119.34
  ai mail is handled by 10 mail.offshore.ai.

[iRomain]

I'm not saying "ai" is not a valid domain. I'm just guessing why people get to a website when they just type "ai".

I'm on my phone now, if you search for the ai entry in the root zone file (https://www.iana.org/domains/root/files) you should find that IP returned by your host command.

Can you try curling "ai" and see if the content returned (if any) is the same as the one from "www.ai"?

[LeoPanthera]

They are the same, but that's not really the point. www has been registered in addition to the entries for the root TLD. You said "the internals of the browser that automatically adds a www in front" - that's irrelevant. host isn't doing that, curl isn't doing that.

[iRomain]

You are right, they added a A record in the root zone file. I didn't know it was allowed.

https://news.ycombinator.com/item?id=31690379

[5ESS]

Did the owners of .com do the same thing?

Because http://com. Works as well.

[captn3m0]

There's a bunch of TLDs with A records, even Google used to point .dev to 127.0.0.53 for a while.

[iRomain]

You are right I didn't know it was allowed

[jmprspret]

I thought 'ai' was valid according to spec, but depending on your browser it may or may not actually go to 'http://ai./'