Five Regular Expression Resources We Can't Live Without

We often get asked about what technical resources we recommend referencing when using or writing regular expressions. In this post, we’re sharing five great resources to help get you started with regular expressions, as well as showcasing some of the ways they can be used.

Claire Williams // December 1, 2020

For those of you who have been with us for a while, you know that regular expressions (or as cool kids say – ‘regex’) hold an important place in our nerdy little hearts and in our actual software.

If you’re already familiar with regular expressions, you know they offer a way for Heretik (and Relativity) to find information you’re looking for across document sets while drastically cutting down time and increasing the accuracy. Depending on how you structure a regular expression tells it exactly how to search for what you want to find. (If you’re wondering what exactly regular expressions are, check out our previous blog post Regular Expressions 101, and then circle back to this one. We dive into much more of the basics over there.)

One of the best things about regular expressions is that they can be written by anyone to find literally anything, and there are plenty of resources that can help you get started. We often get asked about what technical resources we recommend referencing when using or writing regular expressions. In this post, we’re sharing five great resources to help get you started with regular expressions, as well as showcasing some of the ways they can be used. RelOne customers – make sure you check out the end of the article to learn more qualifying a regex composition credit!


This site is for anyone looking to create and test their own regular expressions. Pasting strings of texts from a document you want to pull data points from, you can then create, customize and test your own original expressions to help you perfect what you’re looking for. It’s pretty bare bones, but offers a simple, quick way to test what you’re working on. Check our Regex101 here.


A tutorial and testing site that focuses on explaining how regular expressions work, how they can be used, and how to group expressions to capture information. RegExr has information that defines and explains all parts of regular expressions from beginners to expert-level creators. You can also see others’ regular expressions that have been shared that work with various software systems. Finally, RegExr also has a place to save and log previously created regular expression patterns for additional editing, testing or to use on future documents. Check out RegExr here.


A learning and exercise site that quite literally teaches you the ABC’s of regular expressions. You’ll learn the basics by completing ordered tasks that start you at learning the characters of regular expressions and what they mean, to being challenged to write and create your own expressions based upon the text given and the lessons that were provided previously. Check out RegexOne here.

Heretik’s Regex Library & Use Case Templates

Heretik offers tons of customizable features out of the box. In fact, Heretik Analysis actually comes with built-in regular expressions that automatically find data points such as dates, monetary values, names, countries, percentages, and more. In addition, Heretik customers have access to our Regular Expression Library for more complex regular expressions we’ve written for various types of use cases and/or document types. We’ve also developed a range of use case packages (including LIBOR Remediation, Contract Portfolio Analysis, Force Majeure Review, Business Interruption Insurance, Bankruptcy & Restructuring, Schrems II, Capital Project Management, and more) that include a Relativity workspace template with specific regular expressions teams can use or customize for their projects. Want to learn more about our Regex Library or use case templates? Get in touch with our team here.

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Regular Expression Building Blocks

Because regular expressions are such a powerful and integral part of Heretik, making them easier and more accessible is a core focus of our on-going product roadmap. We recently released a new regex building blocks tool that allows our users to write and combine regular expressions like Legos. Check out the short and sweet tutorial above to learn more about our built-in regex functionalities or our Partner Resource Center for more information!

And that’s our list of five regular expression resources we can’t live without! As helpful as they can be, we also know that specific regex requirements can vary from project to project depending on the content of documents. And while anyone can write or edit regular expressions to suit their needs, they can require a bit more experience to build exactly what you’re looking for.

That’s why in order to offer even more customization, we’ve partnered with Relativity to offer a regex composition credit. What does this mean? Until the end of 2020 (12/31/20) existing RelativityOne customers that sign up for an annual Heretik package are eligible for the regex composition credit. Our teams will then work with yours to write custom and exclusive regular expressions for your specific projects.

If you are interested in seeing more examples of regular expressions in action or want more information about the regex composition credit, click below to get in touch with our team!



Claire is a Marketing Coordinator at Heretik. She recently graduated from Miami University Ohio with a double major in Journalism and Mandarin Chinese. Prior to Heretik, Claire worked at Amdur Productions and for Miami University College of Arts and Science.​