Visualize and test your regular expressions with debuggex.com

I love regular expressions. It’s one of the first things I learned as a programmer. They represent an intriguing mix of intellectual challenge and expressive power. Regexes can condense complex logic into a single line, creating a mental puzzle that feels both elegant and satisfying to solve.

That said, most developers I know don’t share my enthusiasm. Regexes can be hard to read, write, and debug. That’s why I use debuggex.com to help visualize and test my regexes during development.

Debuggex.com

Other regex tools often limit themselves to syntax highlighting, syntax validation, and basic explanations of components. debuggex.com goes further by providing a visual representation of a regex’s components as a graph, making editing and understanding much easier.

Regex of a Docker Compose bind mount entry with named groups

Let’s look at another example with this regex, which is supposed to validate an email address:

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

I don’t know about you, but I can’t understand this at first glance. With debuggex.com, everything suddenly becomes much clearer:

Some email address regex found online

My tips for reading and writing regexes

Aside from using debuggex.com, here are some tips that I’ve found helpful when working with regular expressions:

Use comments: Chances are, you’ll forget what a regex does the next time you read it. Now imagine how hard it would be for your collaborators. Include concrete examples rather than abstract comments.
Use named groups: Explicit group names make your regex more readable and easier to maintain. They also allow you to reference groups by name rather than by index.
Add unit tests: How can you be sure your regex works as intended? By adding unit tests, you can confirm its functionality and avoid regressions. These tests also help document your regex.
Use generative artificial intelligence: Spending half a day writing a regex is not a good use of your time. Nowadays, tools like ChatGPT, Claude, Gemini, and GitHub Copilot can save you a lot of time by generating regexes for you. They can also verify their correctness if you provide a test dataset.