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Regular Expressions for Regular Folk

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This is an experimental “book” about regular expressions. It is largely visual and example-based, as opposed to most regex resources I found while I was learning. I also attempted to choose test cases that highlight some common gotchas. I think it’ll be worth your time.

Screenshot from /chapters/escapes

This book’s intended audience is regex beginners. Some programming experience is assumed. It does not go into advanced regex concepts like engine backtracking and recursive regexes—at least not at the moment.

This is also an open source project, and contributions are welcome.

Read it online.


Translations are welcome, as long as they adhere to the license.

You can choose to publish your translation separately, but we welcome translations on here too!


A single-page version of the book is available. Print it ordinarily. Make sure to enable “Print Background Colors” on Firefox and “Background graphics” (under “More settings”) on Chrome.


Check the releases tab for a list of releases. A PDF version of each release—book.pdf—is present under “Assets”.

Built With


Thanks to all contributors for creating issues, sharing feedback, and creating pull requests!

I referred to RegExr and its community patterns—great resources. I also borrowed some examples from the iHateRegex collection.


Thanks for taking the initiative to contribute to REFRF! 🎉

Please check our Contribution Guide for more information.


Chapter content (chapters/*) is licensed under CC BY-SA 4.0.

The source code for the website is licensed under the MIT License


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