You'd think that the concept of "a URL" would be pretty clearly defined by now, with the internet being what it is today. Well, turns out -- it isn't.
This document is an attempt to describe where and how RFC 3986 (86), RFC 3987 (87) and the WHATWG URL Specification (TWUS) differ. This might be useful input when trying to interop with URLs on the modern Internet.
This document focuses on network-using URL schemes (http, https, ftp, etc) as well as 'file'.
What really strikes me as odd is the interoperability comparison for each "fragment" in the URL;
|Component||Value||Known interop issues exist|
It's amazing a "URL" even works.
I've said it before and I'll say it again: the internet is held together with duct tape. I hope this proposal gets somewhere, it'll make parsing URLs a whole lot easier and more reliable.
Source: URL Interop