build-your-own-x: Learn Programming by Building Technologies
Image: GitHub
"What I cannot create, I do not understand." — Richard Feynman
If you've ever wondered how a database works under the hood, how Git tracks file changes, or how Docker isolates applications — the answer is in this repo.
build-your-own-x is a GitHub repository curated by CodeCrafters that has amassed over 539,000 stars. What's inside? A collection of step-by-step tutorials for building well-known technologies from scratch. All free, all open-source, all available in a variety of programming languages.
In this article, we'll cover everything: what build-your-own-x is, what technologies you can build, how to use the repo, the learning benefits, and real-world use cases. Let's get started!
What Is build-your-own-x?
In short, build-your-own-x is a collection of tutorials that guide you through recreating well-known technologies from the ground up. Not using pre-built libraries or off-the-shelf frameworks — but writing code from scratch to truly understand how everything works.
The repository uses Markdown format and is licensed under CC-BY-4.0 (Creative Commons Attribution), so you're free to use, share, and modify the content as long as you provide proper credit.
Why Is This Repository So Popular?
Here are a few reasons build-your-own-x has become one of the most starred repos on GitHub:
- Completely free — All tutorials are available free online. No paywall, no paid courses.
- Multi-language — Tutorials in Python, JavaScript, Go, Rust, C++, Java, and many other languages.
- Hands-on — No dry theory. You code immediately and produce something you can run.
- Comprehensive — Covers 30+ technology categories, from 3D rendering to operating systems.
- Massive community — With 539K+ stars, this isn't just a repo — it's a movement.
What Technologies Can You Build?
This is the exciting part. build-your-own-x spans dozens of technology categories. Here's a full overview:
🖥️ Systems & Infrastructure
| Technology | What You'll Learn |
|---|---|
| Operating System | Bootloader, kernel, file system, process management |
| Docker | Containers, namespaces, cgroups, process isolation |
| Database | Storage engine, indexing, query processing, SQL |
| Web Server | HTTP protocol, socket programming, request handling |
| Shell | Command parsing, piping, environment variables |
| Network Stack | TCP/IP, routing, packet handling |
🤖 AI & Machine Learning
| Technology | What You'll Learn |
|---|---|
| Neural Network | Backpropagation, forward pass, gradient descent |
| AI Model (LLM) | Transformer architecture, tokenization, training |
| Visual Recognition | Computer vision, image classification |
🎮 Games & Graphics
| Technology | What You'll Learn |
|---|---|
| 3D Renderer | Ray tracing, rasterization, graphics pipeline |
| Physics Engine | Collision detection, rigid body dynamics |
| Game | Game loop, rendering, input handling |
| Voxel Engine | Voxel rendering, chunk management, world generation |
🛠️ Developer Tools
| Technology | What You'll Learn |
|---|---|
| Git | Version control, diffing, merging, object model |
| Text Editor | Buffer management, syntax highlighting, undo/redo |
| Command-Line Tool | Argument parsing, terminal output, scripting |
| Programming Language | Lexer, parser, AST, interpreter/compiler |
| Regex Engine | Finite automata, pattern matching |
🌐 Networking & Communication
| Technology | What You'll Learn |
|---|---|
| BitTorrent Client | P2P protocol, piece management, trackers |
| Search Engine | Crawling, indexing, PageRank, ranking |
| Bot | API integration, message handling, automation |
🔧 Other
| Technology | What You'll Learn |
|---|---|
| Blockchain / Cryptocurrency | Hashing, consensus, Merkle tree, mining |
| Emulator / Virtual Machine | CPU emulation, instruction sets, memory |
| Front-end Framework | Virtual DOM, reactivity, component lifecycle |
| Memory Allocator | malloc/free, heap management, fragmentation |
| Processor | Logic gates, ALU, instruction decoding |
| Template Engine | Parsing, compilation, rendering |
| Augmented Reality | Camera tracking, overlay rendering |
That's a lot! And for each category, there are usually multiple tutorials available in different programming languages. For example, the "Build your own Blockchain" category has tutorials in JavaScript, Python, Go, Java, Ruby, Kotlin, TypeScript, and Rust.
How to Use the build-your-own-x Repo
Step 1: Visit the Repository
Open your browser and navigate to:
https://github.com/codecrafters-io/build-your-own-xStep 2: Pick a Topic That Interests You
In the README, you'll find a table of contents organized by technology category. Click one to jump straight to the relevant section.
Step 3: Choose a Tutorial in Your Preferred Language
Each category contains a list of tutorials from various external sources. Each tutorial is tagged with its programming language, like this:
* [**Python**: _Learn Blockchains by Building One_](tutorial-link)
* [**JavaScript**: _Build your own Blockchain in JavaScript_](tutorial-link)
* [**Go**: _Building Blockchain in Go_](tutorial-link)Just click the tutorial title you want, and you'll be directed to the article, video, or repository with the full tutorial.
Step 4: Start Coding!
Open your favorite code editor (VS Code, Neovim, or whatever you prefer), create a new project, and follow the tutorial step by step. The key is: don't just copy-paste. Read, understand, and experiment with the code you write.
Bonus Tips
- Start small — Don't jump straight to building an operating system. Begin with a simple shell or command-line tool.
- Use a language you already know — Learning new concepts is easier when you're not simultaneously learning a new language.
- Read the external sources — Tutorials in this repo usually link to longer articles or separate repos. Take the time to read them.
- Experiment — After getting the tutorial working, try adding new features or optimizations.
Benefits of Learning with build-Your-Own-X
1. Deep Understanding
This is the biggest benefit. Instead of just knowing how to use a framework or tool, you truly understand how everything works under the hood.
Example: After building a web server from scratch, you'll understand what actually happens when a browser sends an HTTP request. You'll know why WebSocket differs from HTTP, how SSL/TLS works, and why there are limits on concurrent connections.
2. Sharper Problem-Solving
When you've built a regex engine or parser from scratch, debugging issues in other people's code becomes much easier. You have a strong mental model of how complex systems should work.
3. Transferable Skills
The knowledge you gain from build-your-own-x isn't tied to any specific programming language. Concepts like "how a hash table works" or "how an HTTP server handles requests" apply everywhere you write code.
4. An Impressive Portfolio
Imagine telling an interviewer: "I built a simplified version of Redis using Go" or "I created my own programming language with a lexer and parser." That's far more impressive than just saying "I know React."
5. Building Confidence
Many developers experience "impostor syndrome" — feeling like they're not competent enough. By building complex technologies from scratch, you prove to yourself that you can understand and create intricate systems.
6. Reading Open-Source Code Better
After building a simplified version of Git, you'll feel much more confident reading Git's actual source code. After building a mini Docker, you can explore containerd or runc with greater ease.
Use Cases: When Should You Use build-Your-Own-X?
🎓 Use Case 1: Students Wanting to Understand Coursework More Deeply
Courses on operating systems, networking, or databases often feel abstract when you're only reading theory. With build-your-own-x, you can put that theory into practice right away.
Concrete examples:
- Database Course → Build your own Database (C, Go, or Python)
- Operating Systems Course → Build your own OS, Shell, Memory Allocator
- Networking Course → Build your own Network Stack, Web Server
💼 Use Case 2: Developers Looking to Level Up
You can build CRUD apps, but you feel stuck. You want to move into a more senior role or transition into a more challenging area like infrastructure or systems programming.
Concrete examples:
- Want to understand infrastructure → Build your own Docker, Container
- Want to understand databases → Build your own Database, Redis
- Want to break into AI → Build your own Neural Network, AI Model
🧑💻 Use Case 3: Preparing for Technical Interviews
Many tech companies (especially FAANG/MAANG) like to ask fundamental concept questions. With build-your-own-x, you learn in the most effective way possible: by building.
Commonly asked topics:
- How does a hash table work? → Build your own Hash Table
- How does caching work? → Build your own Redis
- How does DNS work? → Build your own DNS Server
🚀 Use Case 4: Building Cool Personal Projects
Tired of the same old to-do apps? Try building something more challenging.
Project ideas from build-your-own-x:
- Build a small search engine for indexing your personal blog posts
- Build a Telegram chatbot that answers questions on a specific topic
- Build a simplified version of Git for tracking file versions
📚 Use Case 5: Becoming a Technical Writer or Educator
If you want to write tutorials or teach programming, the experience of building technologies from scratch provides incredibly valuable insights. You can explain the "why" behind every technical decision.
🏢 Use Case 6: Engineering Teams Wanting Better Onboarding
Tech leads can use build-your-own-x tutorials as an internal curriculum for onboarding new engineers. For example, new hires on an infrastructure team could be asked to build a simplified version of the tools they use every day.
Recommended Starting Points by Level
🟢 Beginner
| Project | Language | Why |
|---|---|---|
| Build your own Shell | Python | Core command parsing concepts, fairly intuitive |
| Build your own Bot | Python/Node.js | Instant gratification, visible results right away |
| Build your own Command-Line Tool | Go/Rust | Learn CLI structure, argument parsing |
| Build your own Web Server | Python/Node.js | Fundamental HTTP protocol, very relevant |
🟡 Intermediate
| Project | Language | Why |
|---|---|---|
| Build your own Database | Go/C | Storage engine, indexing — foundational concepts |
| Build your own Docker | Go | Container networking, namespaces, cgroups |
| Build your own Git | Python/Go | Version control internals, object model |
| Build your own Blockchain | JavaScript/Python | Cryptography, data structures, networking |
| Build your own Regex Engine | Any | Finite automata, parser |
🔴 Advanced
| Project | Language | Why |
|---|---|---|
| Build your own OS | C/Assembly | Kernel, memory management, scheduler |
| Build your own Compiler/Programming Language | Rust/Go | Full compiler pipeline |
| Build your own Neural Network | Python | Math intensive, backpropagation |
| Build your own 3D Renderer | C++/Rust | Linear algebra, graphics pipeline |
| Build your own Processor | Hardware Description Language | CPU architecture, digital logic |
Tips for Getting the Most Out of It
1. Don't Jump Straight to the Solution
Resist the urge to run straight to Stack Overflow or someone else's answer. Try to understand the problem first, read the documentation, and decide on your own approach before looking at the tutorial solution.
2. Build Iteratively
Don't try to build everything at once. Start with the simplest version that actually works, then add features incrementally. For example:
Version 1: Web server that serves a single static HTML file
Version 2: Add routing
Version 3: Add support for POST requests
Version 4: Add error handling
Version 5: Add logging3. Document Your Learning Process
Write a blog post or README explaining what you learned. This helps:
- Lock in your understanding (teaching is the best learning)
- Build a public portfolio
- Help other programmers who want to learn the same thing
4. Compare with the Original Implementation
After building your simplified version, compare it with the real implementation. For example:
- After building a simple web server, read the source code of Express.js or Gin
- After building a simple database, study the architecture of SQLite or LevelDB
5. Join the Community
Discuss your learning process on Twitter, Reddit (r/programming, r/learnprogramming), or Discord. Communities can help when you're stuck and provide motivation to keep going.
Trending Topics in 2026
build-your-own-x keeps up with industry trends. Here are some of the latest additions:
Build your own AI Model (LLM)
With the explosion of ChatGPT and other large language models, tutorials on building an LLM from scratch have become extremely popular. Available tutorials in Python cover:
- Transformer architecture
- Tokenization
- Self-attention mechanism
- Training pipeline
This is especially relevant in 2026 as AI becomes an integral part of nearly all software.
Build your own RAG (Retrieval-Augmented Generation)
RAG is a technique that lets LLMs answer questions based on specific documents. Tutorials from LangChain explain how to build a RAG pipeline from scratch.
Build your own Diffusion Model
For those interested in generative image AI, tutorials on building diffusion models (like those used in Stable Diffusion) are also available.
Frequently Asked Questions
"I'm still a beginner — is this suitable for me?"
Absolutely! Start with something simple like Build your own Bot or Build your own Command-Line Tool. The main requirement is that you know the basics of your chosen programming language.
"How long does it take to complete one tutorial?"
It depends on the complexity and the programming language you choose. A simple tutorial might take 2-4 hours. More complex ones like Build your own OS could take weeks.
"Do I need to master all the programming languages listed?"
Not at all. Just pick one language you're comfortable with and start from there. The great thing about this repo is the wide language selection for every topic.
"How do I contribute to this repository?"
This is a curated list, so the way to contribute is by submitting a pull request that adds a high-quality new tutorial. Make sure the tutorial you propose is step-by-step and shows how to build something from scratch.
"Are the tutorials here production-ready?"
Most of them are not. The goal is learning, not building a production-ready version of the technology. The implementations are intentionally simplified to focus on core concepts.
Conclusion
build-your-own-x isn't just another tutorial repository. It's a programming learning movement that changes how we understand technology. Instead of being a passive user who only knows how to use tools, you become an active builder who understands how everything works under the hood.
With 539K+ stars on GitHub and hundreds of tutorials across various programming languages, there's no reason not to start. Pick a topic that interests you, open your code editor, and start building.
As Richard Feynman said: "What I cannot create, I do not understand."
Start now, and prove that you can both create and understand.
Link: github.com/codecrafters-io/build-your-own-x
License: CC-BY-4.0 (Creative Commons Attribution 4.0 International)
Topics: awesome-list, free, programming, tutorial-code, tutorial-exercises, tutorials
Complete Category List in build-your-own-x
Here's a full list of all categories available in the repo as of August 2026:
- 3D Renderer — Learn ray tracing, rasterization, and computer graphics
- AI Model — Build LLMs, diffusion models, and RAG pipelines
- Augmented Reality — Camera tracking, overlay rendering, and AR interaction
- BitTorrent Client — Peer-to-peer networking, piece management, and BitTorrent protocol
- Blockchain / Cryptocurrency — Hashing, consensus mechanisms, and Merkle trees
- Bot — Build bots for Telegram, Discord, Slack, Reddit, and Twitter
- Command-Line Tool — Argument parsing, terminal UI, and shell scripting
- Database — Storage engine, B-tree, query processing, and SQL parser
- Docker — Containers, namespaces, cgroups, and image layering
- Distributed Systems — Kafka-like systems, CAP theorem, and replication
- Emulator / Virtual Machine — CPU emulation, instruction sets, and register management
- Front-end Framework / Library — Virtual DOM, reactivity system, and component model
- Game — Game loop, physics integration, rendering pipeline, and input handling
- Git — Object model, branching, merging, diffing, and pack files
- Memory Allocator — malloc/free implementation, heap management, and fragmentation handling
- Network Stack — TCP/IP, socket programming, routing, and packet handling
- Neural Network — Backpropagation, activation functions, and gradient descent
- Operating System — Bootloader, kernel, scheduler, and file system
- Physics Engine — Collision detection, rigid body dynamics, and constraint solving
- Processor — Logic gates, ALU, control unit, and instruction decoding
- Programming Language — Lexer, parser, AST, interpreter, and compiler
- Regex Engine — Finite automata, NFA/DFA, and pattern matching
- Search Engine — Web crawling, indexing, PageRank, and ranking algorithms
- Shell — Command parsing, piping, job control, and environment variables
- Template Engine — Template parsing, compilation, and rendering output
- Text Editor — Buffer management, syntax highlighting, undo/redo, and extensibility
- Visual Recognition System — Image classification, object detection, and feature extraction
- Voxel Engine — Voxel rendering, chunk management, and world generation
- Web Browser — HTML parsing, CSS layout, JavaScript engine, and rendering
- Web Server — HTTP handling, socket programming, SSL/TLS, and reverse proxy
With 30+ categories, you could spend years and still find something new to learn. Each category has at least 3-5 tutorials, and popular categories like Blockchain or Database have 10+ different tutorials.
This article was updated in August 2026. For the latest version of the build-your-own-x repository, visit the repo directly on GitHub.