Regular expression for checking website url

Question

I need to check the web address, using regular expression.

if user type url as

1. www.test.com
2. http://www.test.com
3. https://www.test.com

Answer 1

This is a pretty basic expression for testing domain names:

@^(http\:\/\/|https\:\/\/)?([a-z0-9][a-z0-9\-]*\.)+[a-z0-9][a-z0-9\-]*$@i

Should match:

domain.com
www.domain.com
http://domain.com
https://domain.com