Matching a web address through regex

I want to match a web address through regex which should capture http://www.google.com as well as www.google.com i.e. with and without protocol.

From stackoverflow

• Try RegexLib.

  Cerebrus : Exactly the reply (and the link) I would have provided!

• Read RFC 3986. It is not just as easy as you might think it is. The job is easier if you only have a small set of URLs to parse.

  John Sheehan : You can get 'good enough' though, so this answer isn't particularly helpful

  dirkgently : Its about as good an answer as there was one without full problem specification. To the extent of being a competitor for the top answer. The problem is few people read the RFCs and I having read one and written a IPV6 parser know how hard the job is.

• Well it's going to depend on exactly what you want to capture ("FTP"? "/index.htm"?) because a general URI capture based on the RFC standard is very hard, but you could start with:

  /^((https?\:\/\/)?([\w\d\-]+\.){2,}([\w\d]{2,})((\/[\w\d\-\.]+)*(\/[\w\d\-]+\.[\w\d]{3,4}(\?.*)?)?)?)$/
  

  Complicated see?

• Why not

  /google\.com/
  

  ?

  It catches http://www.google.com , www.google.com , and even google.com for free! :-)

  annakata : It also catches "Well I guess I could try searching for this regex on google.com, nah SO is better than google these days. Hmm, I wonder what's for lunch. Mmmm. Bacon"

  MSalters : Which, if you enter it in most browsers will bring you to google :)

  John Sheehan : SO is meant to be a reference so that when you search google, you end up here instead of another crappy site. So this question is fine.

  Igor Oks : @John: Please stop making paranoic comments and donevotes. This was a legitimate answer, advising how to match specific domain names (e.g. google.com).

• See answers to Getting parts of a URL (Regex). It may provide you with suitable answers.

  Note: not an exact duplicate.