Open Source is free and Open Source.

The website prototype is written in Ruby using the Sinatra web framework. It is licensed under the GNU Affero General Public License.

The command-line client is written in Go, and distributed under the MIT license.

The exercises in the various languages are also released under the MIT license.

An overwhelmingly large number of people have contributed to the codebase.

An even larger number of people have contributed through participation; by completing exercises and participating in the discussions about code.

Individual exercise submissions are owned by their author, and may or may not be distributed under an open source license.


Exercism is still a prototype, and we are always experimenting with the basic feature set. The goal is to develop a V1 of the product from scratch using everything that we've learned building and using the prototype.

The V1 will be built using well-known frameworks and conventions to minimize the barrier to contributing.

Origin of Exercism's name

What's with the name "Exercism"?

Despite being one vowel away from "exorcism", the name has nothing to do with demons or fixing "evil code".

Instead, it's a pun on exercise. The way Katrina came to think about each exercise is that they are small, trivial, and seemingly simple. However, when it comes to solving an exercise, the devil is often in the details. In other words, that simple exercise is suddenly more challenging once you think about the finer details.

Following that idea, the icon came into existence after Katrina mentioned the idea of the devil is in the details to a designer.

To learn more about what it means for the devil to be in the details, check out these talks by Katrina: Overkill, Succession

Creator: Katrina Owen

Katrina is a polyglot developer and Ruby Hero award winner who accidentally became a developer while pursuing a degree in molecular biology.

She began nitpicking code back in 2006 while volunteering at JavaRanch, and got hooked. When programming, her focus is on automation, workflow optimization, and refactoring. She cares deeply about open source and contributes to several projects outside of exercism.