codecrafters-io/build-your-own-x

What it is

This is a Markdown index of step-by-step guides for reimplementing familiar technologies yourself, from a 3D renderer and a BitTorrent client to a database, shell, Git, operating system, or programming language. Each category groups tutorials by implementation language and links to the original article, book, video, or repository. It is aimed at programmers who learn by building and want a curated starting point rather than a search result list.

The repository contains the index itself, not runnable source code. Tutorials are third-party material, so their depth, language, and prerequisites differ widely; the README is where you choose the project that matches your interests.

Getting started

1. Open the README and scan the category list.
2. Pick a category, for example Build your own Database, Build your own Shell, or Build your own AI Model.
3. Read the language label beside each entry, then follow the linked tutorial and set up that tutorial's own toolchain.

No installation or build step is required for this repository. The repository is also open to contributions: submissions arrive as pull requests or issues, and pending submissions are reviewed through comments and reactions.

Constraints

• Every tutorial is maintained by its own author, with its own license and tool versions; the index does not guarantee that links stay current.
• Difficulty and scope vary a lot within a category. A "text editor" tutorial may mean a low-level buffer and key-handling exercise or a GUI wrapper around an existing component.
• The index is licensed under CC0, so reuse of the list itself is unrestricted.

HotRepo's take

This is one of the most-starred learning indexes on GitHub, with roughly 535k stars in the August 2026 daily records and daily gains around 670–710 stars. It has also appeared on Hacker News several times since 2022, most prominently a July 2022 thread with 528 points and 82 comments. The criticism there is relevant: commenters noted that tutorial quality varies sharply within categories and suggested ratings or filters, while others argued that different interpretations of "build your own" are legitimate. The index is best treated as a discovery layer whose entries need judging individually, not as a graded curriculum.