Build Your Own X is an open-source collection of blog posts, tutorials, and resources that teach you how to recreate popular technologies using different programming languages. 

The idea is that you will become a better programmer or work on mastering a language through the exercise of building an existing technology.  

According to Stack Overflow’s 2023 Developer Survey, 80% of developers use online resources to learn to code, up from 70% in 2022 and 60% in 2021.  

The collection includes resources for building the following technologies: 3D renderers, augmented reality, BitTorrent clients, blockchain and cryptocurrency, bots, command-line tools, databases, Docker, emulators and virtual machines, front-end frameworks, games, Git, network stacks, neural networks, operating systems, physics engines, programming languages, Regex engines, search engines, Shell, template engines, text editors, visual recognition systems, voxel engines, web browsers, and web servers.

The tutorials span a wide range of languages, including C++, C#, Go, Java, JavaScript, Python, Rust, and more.

The resource was created by CodeCrafters, which is a company that offers an app that guides you through the process of this learning. At the time of this writing, it has 205k stars on GitHub.