That's John Gruber’s regex pattern for matching URL's (⌐■_■).

This is an example of the old adage that “When you use a regex to solve a problem, you end up with two problems.”

Looks like an URL matcher of some sorts, not limited to HTTP. Kudos for handling parentheses as valid URL characters.

No

As visualized by Regex Vis [1]

As visualized by Regexper [2]

The regex fucks with the markdown, so I had to put them in code tags:

[1] https://regex-vis.com/?r=%5Cb%28%28%3F%3A%28%3F%3A%5Ba-z%5D%5B%5Cw-%5D%2B%3A%29%3F%28%3F%3A%2F%7B1%2C3%7D%7C%5Ba-z0-9%25%5D%29%7Cwww%5Cd%7B0%2C3%7D%5B.%5D%7C%5Ba-z0-9.%5C-%5D%2B%5B.%5D%5Ba-z%5D%7B2%2C4%7D%2F%29%28%3F%3A%5B%5E%5Cs%28%29%3C%3E%5D%2B%7C%5C%28%28%5B%5E%5Cs%28%29%3C%3E%5D%2B%7C%28%5C%28%5B%5E%5Cs%28%29%3C%3E%5D%2B%5C%29%29%29*%5C%29%29%2B%28%3F%3A%5C%28%28%5B%5E%5Cs%28%29%3C%3E%5D%2B%7C%28%5C%28%5B%5E%5Cs%28%29%3C%3E%5D%2B%5C%29%29%29*%5C%29%7C%5B%5E%5Cs%60%21%28%29%5C%5B%5C%5D%7B%7D%3B%3A%27%22.%2C%3C%3E%3F%C2%AB%C2%BB%E2%80%9C%E2%80%9D%E2%80%98%E2%80%99%5D%29%29

[2] https://regexper.com/#\b((?:(?:[a-z][\w-]%20:)?(?:\/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()%3C%3E]+|\(([^\s()%3C%3E]+|(\([^\s()%3C%3E]+\)))*\))+(?:\(([^\s()%3C%3E]+|(\([^\s()%3C%3E]+\)))*\)|[^\s%60!()\[\]{};:'%22.,%3C%3E?%C2%AB%C2%BB%E2%80%9C%E2%80%9D%E2%80%98%E2%80%99]))

At first glance IP address or URL, embedded in HTML, whatever it is, it's a doozy. I wonder what the performance of it is like.

Looks like the hacking mini game in Fallout 4.

Whatever this is supposed to match, I bet the bycatch is bigger than tuna fishing.

URLs in an HTML document that aren't namespaces or otherwise enclosed?

Hold on, let me draw up the NFA

Probably documents from HP’s atrocious support site

:(

Is it a rick roll?