Let’s go ahead and write some regex to validate a URI in Ruby:

URI.regexp

That’s it!

We can use it like so

URI.regexp.match(my_uri)

If you have a look at the output of URI.regexp in irb, you’ll see the pattern that’s used to match against. It’s relatively complex, but each capture group is documented.

1. Scheme
2. Opaque (e.g. scheme:foo/bar)
3. User Info
4. Host
5. Port
6. Registry
7. Path
8. Query
9. Fragment

irb(main):001:0> URI.regexp.match("http://username:password@foo.bar:80/baz.html?query=string#fragment")
=> #<MatchData "http://username:password@foo.bar:80/baz.html?query=string#frag" 1:"http" 2:nil 3:"username:password" 4:"foo.bar" 5:"80" 6:nil 7:"/baz.html" 8:"query=string" 9:"frag">