I need a url validator regex with this criteria:

• protocol (HTTP, HTTPS) is optional. But if any protocol is given, it must be in the correct format, i.e. protocol:domain, or protocol://domain.
• www is optional
• it's possible to use direct IP address for this.

So based on the criteria, these should pass:

• http://www.google.com
• google.com
• abc.def.ghi/hij
• https:216.239.38.120
• 216.239.38.120

These should not pass:

• hello
• hello/world
• abc://def.ghi
• ftp:google.com

The closest regex I've found is from here:

^((?:.|\n)*?)((http:\/\/www\.|https:\/\/www\.|http:\/\/|https:\/\/)?[a-z0-9] ([\-\.]{1}[a-z0-9] )([-A-Z0-9.] )(/[-A-Z0-9 &@#/%=~_|!:,.;]*)?(\?[A-Z0-9 &@#/%=~_|!:‌​,.;]*)?)

But unfortunately, google.com doesn't pass. It needs to have www. as a prefix. Can you improve this regex so www. becomes optional?

CodePudding user response：

It looks like the following pattern matches your criteria:

^(?:https?:\/\/(?:www\.)?|https:(?:\/\/)?)?\w (?:[-.]\w ) (?:\/[^\/\s] )*$

See the regex demo. Details:

• ^ - start of the string
• (?:https?:\/\/(?:www\.)?|https:(?:\/\/)?)? - an optional sequence of:
  • https?:\/\/(?:www\.)? - http or https, :// and then an optional www. substring
  • | - or
  • https:(?:\/\/)? - https: and then an optional // string
• \w - one or more word chars
• (?:[-.]\w ) - one or more sequences of a . or - followed with one or more word chars
• (?:\/[^\/\s] )* - an optional sequence of a / an then one or more chars other than / and whitespace
• $ - end of string.