If you're looking to contribute to freeCodeCamp or understand how their challenge system works, this walks you through the entire stack. It covers the YAML-based curriculum format they use for challenges, the Fastify API backend, and the Gatsby React frontend. You'll find practical details on creating new challenges with the helper scripts, writing test assertions, and setting up the local development environment with MongoDB and GitHub OAuth. The challenge structure is well documented with concrete examples showing how hints, seeds, and solutions map to the learning experience millions of users see. It's thorough enough that you could actually ship a pull request after reading through it, which is rare for contribution guides.
npx skills add https://github.com/aradotso/trending-skills --skill freecodecamp-curriculum