Instead of thinking of the regex yourself, there are some Verbs you can use to build the regex and run it.
In PseudoCode:
CreateVerbalExpressions() StartOfLine() Then("http") Maybe("s") Then("://") Maybe("www.") AnythingBut(" ") EndOfLine() /* Create an example URL */ IsMatch("https://www.google.com") --> true IsMatch("www.google.com") --> false