TypeScript Error Simulator
Type Safety Explorer
Enter a simple function to see how TypeScript catches errors before runtime compared to JavaScript.
When you open Visual Studio Code, you don’t see the code behind it. But if you’ve ever wondered what powers this lightweight, fast, and incredibly popular code editor, the answer isn’t what you might expect. VS Code isn’t built with Python, JavaScript, or even C++. It’s built with TypeScript.
That’s right. The same language millions of developers use to write clean, scalable web applications is the very language that runs the editor they use every day. Microsoft chose TypeScript - a superset of JavaScript that adds static typing - to build VS Code from the ground up. Why? Because TypeScript helps manage complexity at scale. VS Code has over 20,000 files of code, hundreds of extensions, and runs on Windows, macOS, and Linux. Without strong typing and structure, maintaining that codebase would be a nightmare.
How TypeScript Powers VS Code
TypeScript compiles down to JavaScript, which means VS Code runs in a JavaScript environment. But TypeScript adds something crucial: type safety. When you write a function in TypeScript, you can define what kind of data it expects and returns. This catches errors before the code even runs. For a tool as complex as VS Code, where one small bug can crash the entire editor, that kind of reliability is non-negotiable.
Microsoft started building VS Code in 2015, and TypeScript had just gained serious traction in the developer community. Teams at Microsoft had already used it internally for projects like Azure Portal and Office Online. They saw how TypeScript reduced bugs and improved developer productivity. So when they needed a new editor that could handle modern web development workflows - with IntelliSense, debugging, Git integration, and extension support - TypeScript was the obvious choice.
Today, over 90% of VS Code’s core codebase is written in TypeScript. Even the UI components, the file explorer, the terminal, and the settings panel are all built with TypeScript components. It’s not just the logic - it’s the whole interface.
The Role of Electron
But TypeScript alone doesn’t make VS Code run on your desktop. That’s where Electron comes in. Electron is a framework that lets developers build desktop applications using web technologies: HTML, CSS, and JavaScript. Think of it as a browser engine wrapped inside a native app window.
VS Code uses Electron to render its interface. The editor’s UI is essentially a web page running inside a Chromium browser window. This means the sidebar, the status bar, the search panel - everything you see - is built with HTML and CSS, styled like a web app but behaving like a desktop program.
Electron gives VS Code cross-platform compatibility without having to rewrite the UI for each operating system. Instead of writing separate code for Windows, macOS, and Linux, Microsoft writes one UI layer and lets Electron handle the rest. This is why VS Code looks and feels almost identical across all three platforms.
But Electron has a reputation for being heavy. Why doesn’t VS Code feel slow? Because Microsoft optimized everything. They stripped out unnecessary features, lazy-loaded components, and used native OS APIs where possible. For example, file system access uses the operating system’s native file APIs instead of going through JavaScript. That’s why VS Code opens in under a second on most machines, even though it’s built on web tech.
Why Not Just Use JavaScript?
You might ask: if TypeScript compiles to JavaScript, why not just write it in plain JavaScript? The answer is scale. JavaScript is flexible - too flexible for large projects. Without types, you can pass a string where a number is expected, forget to initialize a variable, or accidentally overwrite a function. These bugs are hard to catch until runtime.
In a codebase as big as VS Code’s, those bugs add up fast. TypeScript forces developers to be explicit. If a function expects a boolean and you pass a number, the editor flags it before you even save the file. That kind of early feedback saves hours of debugging.
Also, TypeScript has amazing tooling. IntelliSense in VS Code works so well because the editor itself is built with TypeScript. The same code completion, hover documentation, and refactoring tools that help you write JavaScript are powered by the same type system that runs the editor. It’s a self-reinforcing loop: the editor helps you write better TypeScript, and better TypeScript makes the editor better.
Extensions Are Also Built With TypeScript
One of VS Code’s biggest strengths is its ecosystem of extensions. There are over 40,000 extensions available in the marketplace. And guess what? Most of them are written in TypeScript.
Microsoft made it easy for developers to build extensions using the same tools they use to build VS Code. The VS Code API is documented in TypeScript, and the extension development kit (EDK) comes with TypeScript templates. This means extension developers get the same type safety, IntelliSense, and debugging tools as the core team.
Want to create a new language syntax? Write it in TypeScript. Want to add a custom debugger? Use TypeScript. Want to integrate with GitHub? The API is typed, so you know exactly what parameters to pass. This consistency is why VS Code extensions are so reliable compared to older editors.
What About the Performance?
Some people still think “web-based” means “slow.” But VS Code proves that’s not true. Here’s how it stays fast:
- Renderer process: Handles the UI. Lightweight, runs on Chromium.
- Main process: Manages file system, extensions, and core features. Separated from the UI for stability.
- Extension host: Runs each extension in its own process. If one crashes, it doesn’t bring down the whole editor.
- Memory management: VS Code only loads what you need. Open a 10MB file? It doesn’t load the whole thing into memory at once.
Compare that to older editors like Notepad++ or Sublime Text. They’re fast, but they can’t match VS Code’s intelligence. VS Code understands your code. It knows what a function is, what variables are in scope, and what methods are available. That’s not magic - it’s TypeScript and a powerful language server.
Other Tools Built the Same Way
VS Code isn’t alone. Many modern desktop apps use the same stack:
- Slack - Built with Electron and TypeScript
- Discord - Uses Electron for its desktop app
- GitHub Desktop - Entirely built with TypeScript and Electron
- Atom - The predecessor to VS Code, also built with Electron (but abandoned in 2022)
The pattern is clear: if you want to build a cross-platform desktop app with modern tooling, Electron + TypeScript is the go-to stack. It’s not the only option, but it’s the most mature, well-supported, and widely adopted.
What Could Replace It?
Is this stack perfect? No. Electron apps tend to use more memory than native apps. That’s why Microsoft is experimenting with alternatives. In 2024, they started testing a new renderer called WebView2 on Windows, which uses Microsoft Edge’s Chromium engine but integrates more tightly with the OS. It’s lighter and faster.
There’s also talk of moving parts of VS Code to Rust or Go for performance-critical components. But the UI? That’s staying in TypeScript. Why? Because changing it would break thousands of extensions and force millions of developers to relearn their tools.
VS Code’s architecture is a lesson in pragmatism. It’s not about using the “best” language. It’s about using the right tool for the job - and TypeScript, paired with Electron, delivers the perfect balance of power, speed, and maintainability.
Why This Matters for You
If you’re learning to code, knowing that VS Code is built with TypeScript isn’t just trivia - it’s useful. It tells you that TypeScript is not just for big companies or enterprise apps. It’s for real, everyday tools you use to write code. If Microsoft trusts TypeScript to power their flagship editor, maybe you should too.
Learning TypeScript gives you more than just better code. It gives you insight into how the tools you use every day are built. And if you ever want to extend VS Code - write your own theme, add a new snippet, or build a custom linter - you’ll need TypeScript. The documentation, the APIs, the examples - they’re all written in TypeScript.
This isn’t just about an editor. It’s about the direction of modern software development. The line between web and desktop is fading. And TypeScript is the bridge.
Is VS Code written in Python?
No, VS Code is not written in Python. While Python is one of the most popular languages you can use inside VS Code - thanks to extensions - the editor itself is built with TypeScript and Electron. Python is a language you write code in, not the language that powers the editor.
Can I build my own editor like VS Code?
Yes, you can. Since VS Code is open source, you can fork it on GitHub and modify it. But building a full-featured editor from scratch is a massive project. If you want to start small, use Electron and TypeScript to create a basic text editor with syntax highlighting. Microsoft’s VS Code Extension API documentation gives you step-by-step guides to build custom features. Many developers have created lightweight editors using this stack - like CodeSandbox’s desktop app or custom IDEs for specific languages.
Why does VS Code use Chromium?
Chromium is the open-source browser engine behind Google Chrome and Microsoft Edge. VS Code uses it because it provides a reliable, fast, and standards-compliant way to render web content. Instead of building a custom UI toolkit for every operating system, Microsoft leverages Chromium to draw buttons, menus, and panels using HTML and CSS. This saves time and ensures consistent behavior across Windows, macOS, and Linux.
Does VS Code run slower because it’s built with web tech?
Not noticeably. VS Code is optimized to be fast. It separates the UI from core logic, loads only what’s needed, and uses native OS APIs for file access. Many users report it launches faster than older editors like Sublime Text. While Electron apps generally use more RAM than native apps, VS Code’s memory usage is well-managed. For most developers, the trade-off - a powerful, extensible editor - is worth it.
Is TypeScript only used for web development?
No. While TypeScript started as a web language, it’s now used everywhere. VS Code is built with it. Electron apps use it for desktop software. Backend services in Node.js are written in TypeScript. Even mobile apps using frameworks like React Native can use TypeScript. Its type system makes it ideal for any project where code quality and maintainability matter - not just websites.