There are many out there, but I have two particular favourites.
- For simple testing when building a regex, I like to use 'RegexBuilder'. It has a very simple and quick off the mark interface where you can start typing your regex with 2 testing texts to see if it is working properly:
- For more advanced testing data, or to check the output based on replaces, splits, plus many other useful features, I like to use 'The Regulator'. This has a lot of useful functionality and will help you building regular expression syntax if you are unsure.
I would recommend having both of these programs, as they both have their uses, they are both easy to use and between them can cater for most (if not all) of your regular expression testing needs!