Online regular expression tester: http://www.freeformatter.com/regex-tester.html
Tested against ^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$
as a regular expression to check on the validity of a particular URL. Entry tested: 184.149.5.45
Result: “Fully matches the source string!”.
polonus