How to validate a complete and valid url using Regex

Question

I have a URL validation method which works pretty well except that this url passes: "http://". I would like to ensure that the user has entered a complete url like: "http://www.stackoverflow.com".

Here is the pattern I'm currently using:

"^(https?://)"
+ "?(([0-9a-z_!~*'().&=+$%-]+: )?[0-9a-z_!~*'().&=+$%-]+@)?" //user@ 
+ @"(([0-9]{1,3}\.){3}[0-9]{1,3}" // IP- 199.194.52.184 
+ "|" // allows either IP or domain 
+ @"([0-9a-z_!~*'()-]+\.)*" // tertiary domain(s)- www. 
+ @"([0-9a-z][0-9a-z-]{0,61})?[0-9a-z]\." // second level domain 
+ "[a-z]{2,6})" // first level domain- .com or .museum 
+ "(:[0-9]{1,4})?" // port number- :80 
+ "((/?)|" // a slash isn't required if there is no file name 
+ "(/[0-9a-z_!~*'().;?:@&=+$,%#-]+)+/?)$"

Any help to change the above to ensure that the user enters a complete and valid url would be greatly appreciated.

Answer 1

Why not use a urlparsing library? Let me list out some preexisting url parsing libraries for languages:

• Python: http://docs.python.org/library/urlparse.html
• Perl: http://search.cpan.org/dist/URI/URI/Split.pm
• Ruby: http://www.ensta.fr/~diam/ruby/online/ruby-doc-stdlib/libdoc/uri/rdoc/classes/URI.html#M001444
• PHP: http://php.net/manual/en/function.parse-url.php
• Java: http://download.oracle.com/javase/1.4.2/docs/api/java/net/URI.html#URI(java.lang.String)
• C#: http://msdn.microsoft.com/en-us/library/system.uri.aspx

Ask if I'm missing a language.

This way, you could first parse the uri, then check to make sure that it passes your own verification rules. Here's an example in Python:

url = urlparse.urlparse(user_url)
if not (url.scheme and url.path):
    raise ValueError("User did not enter a correct url!")

Since you said you were using C# on asp.net, here's an example (sorry, my c# knowledge is limited):

user_url = "http://myUrl/foo/bar";
Uri uri = new Uri(user_url);
if (uri.Scheme == Uri.UriSchemeHttp && Uri.IsWellFormedUriString(user_url, UriKind.RelativeOrAbsolute)) {
    Console.WriteLine("I have a valid URL!");
}

Answer 2

This is pretty much a FAQ. You could simply try a search with [regex] +validate +url or just look at this answer: What is the best regular expression to check if a string is a valid URL