Regex101 allows you to create, debug, test and have your expressions explained for PHP, PCRE, Python, Golang and JavaScript. The website also features a community where you can share useful expressions.
Source: Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript
Found this handy tool a while back when I was trying to create a .runsettings file for defining Code Coverage analysis of builds.
In TFS2015, a .runsettings is used to define what is included/excluded in the code coverage analysis. You can specify assembly file paths, names of functions, attributes on code elements, etc. The way you specify those things is by using regular expressions.
Until that day, I had only heard about regular expressions.
I had no idea how to use them…nor how to create one properly.
Then I find RegEx101. This site not only helped me to create the regular expressions I needed, but explained them along the way. On top of that, I was able to create test cases for my expressions right on the same page. So as I wrote a more complex expression, I could test it often and make sure I wasn’t regressing while adding complexity.
Great tool with lots of great information to quickly get you up to speed on creating regular expressions.