build-your-own-x is the codecrafters.io curated index of tutorials that teach you to rebuild familiar technologies from scratch: your own Git, your own React, your own database, your own Redis, your own Docker, your own compiler. Pedagogical rebuilds, not toy demos: each tutorial ends with a working thing you wrote yourself.
View build-your-own-x on GitHub
- 531,502 stars
- 50,276 forks
- Markdown index
- No license (curated links)
build-your-own-x: The format that makes the value
Each entry is a single link to a tutorial that walks through building one technology from scratch: not “explain how Git works,” but “here are 12 commits that end with a working Git implementation.” Most are multi-part blog posts; some are full books (most famously Crafting Interpreters by Robert Nystrom, which is the canonical “build your own programming language” text and is linked from this repo).
The pedagogical bet: rebuilding a tool from scratch teaches you more in 20 hours than six months of using it. The repo doesn’t claim the rebuilds are production-ready; it claims they teach the architecture.
Categories by what you build
Tutorials are grouped by target technology. Highlights: build your own 3D Renderer (ray tracers, rasterizers, WebGL), Blockchain / Cryptocurrency (proof-of-work coins in <500 lines), Database (B-trees, LSMs, SQLite clones), Docker (Linux namespaces + cgroups from scratch), Game (engine, physics, MMO server), Git (multiple tutorials at different depths), Network Stack (TCP/UDP from raw sockets), Operating System (from bootloader to userspace), Programming Language (interpreters, compilers, VMs), Regex Engine, Search Engine, Shell, Text Editor, Version Control, Web Browser (a real toy browser with HTML parsing, layout, and JS), and more.
Each link goes to an external tutorial. Codecrafters maintains the index, not the content. The linked tutorials range from 30-minute reads to multi-month projects.
Codecrafters connection
The repo is maintained by the team behind codecrafters.io, a paid platform that turns the same “build it from scratch” idea into interactive challenges (build Redis, build Git, build a SQLite clone, with autograded tests). The repo is the free index; the platform is the paid guided version. The index doesn’t upsell; it’s the standalone free resource, but the commercial connection is why the repo gets consistent maintenance.
How to actually use it
Pick one technology you use daily and don’t deeply understand. Bookmark its tutorial. Block a weekend. Build the thing. Then do it again with a different tech. The compounding effect over a year is more architectural depth than most bootcamps or courses deliver, because every tutorial forces you to confront the trade-offs the original designers made.
build-your-own-x is the rebuild-from-scratch index. Pick one technology, do one tutorial, and you’ll understand the architecture in a way no amount of usage would have taught you.