I almost get the impression that the only single restriction to urls is having http(s):// at their beginning. Also reminds me on this interesting collection of

I almost get the impression that the only single restriction to urls is having http(s):// at their beginning. Also reminds me on this interesting collection of unusual urls (and regular expressions) https://mathiasbynens.be/demo/url-regex https://mathiasbynens.be/demo/url-regex