Which characters make a URL invalid?

Question

Which characters make a URL invalid?

Are these valid URLs?

• example.com/file[/].html
• http://example.com/file[/].html<

Answer 1

Not really an answer to your question but validating url's is really a serious p.i.t.a You're probably just better off validating the domainname and leave query part of the url be. That is my experience. You could also resort to pinging the url and seeing if it results in a valid response but that might be too much for such a simple task.

Regular expressions to detect url's are abundant, google it :)