I want to locate urls without protocols in the text, and then add the protocol before them. This means I don't want urls that begin with http(s):// or http(s)://www., only the kind of example.com. I'm aware that I might accidentally match with any text1.text2 if I forgot to add a space after a period, so I came up with some rules to make it more like an actual url:


  • (?<=^|\s) The URL should be after the newline or a space.
  • \w*-?\w+ The domain part, could have a dash (-) or not. Since it's after a newline or space, it removes the protocol.
  • [a-z]{2,} The extension, should be more than 2 letters
  • \S* The rest of the URL

It works well to match example.com or example.com/x1/x2 and not https://example.com. But I think it's a bit clumsy, and it fails if there is . or , after the url.

How can I achieve the same goal more elegantly? I don't need to match urls like Are there some loopholes in the above rules that I haven't yet considered?

  • \$\begingroup\$ Duplicate of this stack overflow question: stackoverflow.com/questions/3809401/… \$\endgroup\$ Sep 1, 2021 at 8:00
  • \$\begingroup\$ (?<!\S) in place of (?<=^|\s) (with this simple negation you avoid the alternation). If you want to avoid a dot (that ends a sentence), change the last \S* to \S*(?<![.]). (But whatever you do, don't dream, it can't be perfect even if your pattern fully and precisely describes the URL syntax. \$\endgroup\$ Sep 2, 2021 at 17:29

1 Answer 1


For elegance, I would put at least one line of comment pointing to this; https://datatracker.ietf.org/doc/html/rfc1034#section-3.5

You will notice that there is no limit on the top level domain (Belgian, Dutch, and French domains would like to have a word with .be, .nl, and .fr)

It's unclear if your regex deals well with subdomains

Personally, I would break out the regex in to it's components, following the URL I provided.


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