This
stunning regex tool website is an invaluable tool for anyone who uses complicated regexes a lot.
This web-based visual regex engine is superbly designed. You can give it a scenario / test input text, put in your regex and it will apply the regex and show you the result. It analyses, checks and explains your regex documenting every part of it so if you don’t know what you’re doing or worse think you know and have got it wrong, then the analysis will set you straight.
It support various regex engines with different capabilities and different dialects so you can check if certain marginal features are available with the regex dialect / engine you are using. There is an engine / dialect selector setting that controls this.
There is a stunning debugger that will run you through the operation of the regex step by step so you can see where you are going wrong.
I don’t know what I would do without this site, particularly the facility where you can easily set up a setup scenario and check output so as to debug your regex against a variety of cases.
I use it all the time and in fact I rely on it so much that I make a donation to them when I can. Unfortunately I’m pretty broke these days since I’m not working.
* Another tip: I also use this
regex reference site when I forget what’s what.
I keep forgetting the syntax of certain things. Also thanks to this site I have discovered some advanced features that I had never heard of, such as the mode whatever it’s called where (literal textual) whitespace in regexes is ignored, so that you can break a regex up to format it for readability, and in this mode one can even insert comments in parts of a particularly grim and complex longwinded regex. (One just has to use the likes of '\s' for example in relevant places instead of putting in a significant literal space character.)