In an earlier thread I was claiming that <a href="http://ai/" rel="nofollow">http://ai/</a> was no longer operating, but I belatedly learned that this is because systemd's DNS resolver has hard-coded a refusal to look up addresses with a single label from servers outside the LAN. I misinterpreted the lack of results as implying that it had been removed upstream.<p><a href="https://news.ycombinator.com/item?id=27157712" rel="nofollow">https://news.ycombinator.com/item?id=27157712</a><p>So, (1) there is another site that is as short as the one you mentioned, and (2) Linux systems that default to using systemd-resolve won't be able to see either of them!
I almost get the impression that the only single restriction to urls is having http(s):// at their beginning.<p>Also reminds me on this interesting collection of unusual urls (and regular expressions)
<a href="https://mathiasbynens.be/demo/url-regex" rel="nofollow">https://mathiasbynens.be/demo/url-regex</a>
This is very cool and I have 0% idea how it works. My work's network actually blocks this as 'Unknown', but I'll check it when I get home.