developmentintermediate

WebContainers

Technology that runs a full development environment inside your browser — no installation needed.

💡 In plain English: WebContainers are like running a whole computer inside a browser tab — so you can code without installing anything.

Quick answer

WebContainers, built by StackBlitz, run a complete Node.js environment inside a browser tab using WebAssembly. This is the technology powering Bolt.new — when you open Bolt and start building, a full development environment boots in your browser in seconds. No installation, no terminal setup, works on any device including Chromebooks.

What is WebContainers?

Setting up a development environment traditionally takes 30+ minutes: install Node.js, configure npm, deal with path issues. WebContainers skip all of that by running Node.js directly in the browser.

Built by StackBlitz, WebContainers use WebAssembly to run a sandboxed Node.js runtime in a browser tab. npm install, file system access, and dev server — all running client-side.

The limitation: native npm packages that require compilation (bcrypt, sharp) don't work. Use pure-JavaScript alternatives instead.

In Vibe Coding

Bolt.new runs on WebContainers. When you open bolt.new, a full Node.js environment boots in your browser. This is why npm install runs in the browser and your app previews instantly. Limitation: native packages like bcrypt and sharp don't work — use bcryptjs and Cloudinary instead.

Example

For example: You open Bolt.new on a Chromebook with nothing installed. Within seconds, a full development environment is running in your browser tab — no downloads, no setup, no terminal commands.

Native package alternatives for WebContainers

# This FAILS in Bolt.new (requires native compilation)
npm install bcrypt
# Use this instead (pure JavaScript)
npm install bcryptjs

# This FAILS in Bolt.new
npm install sharp
# Use Cloudinary API instead
npm install cloudinary

Related Terms

npm

An app store for code that other developers have built.

Terminal

The black window that looks like a hacker movie.

Deploy

Making your app live on the internet for real.

Related Guides

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Frequently Asked Questions

Packages requiring native C++ compilation (bcrypt, sharp, canvas) can't run in WebAssembly. Use pure JavaScript alternatives.

Currently only Node.js and related JavaScript runtimes. Python, Ruby, and other languages are not supported.