Native runtimes for the browser

Browser runtimes for AI coding CLIs, Node.js, Python, C/C++, Java, Flash, and x86 binaries via WebAssembly.

Interested in any of our technologies, or generally in compilers, virtual machines, or WebAssembly?

👉 Join our Discord!

Sandboxed runtimes for browser-based execution

Website · Repository · Documentation

• Entirely client-side: instant startup
• Language support: Node.js available. Python and Ruby support planned.
• Supports inbound and outbound networking
• Expose HTTP endpoints publicly using Portals
• Run multiple processes or services in parallel with true concurrency
• Embed coding CLIs in your web project
• Persistent filesystem stored locally in the browser
• Ideal for interactive tutorials, quick experiments, and shareable development environments

Run AI coding CLIs in the browser, client-side

Live demo · Repository

• Supports Claude Code and Gemini CLI, with Codex and OpenCode coming soon
• Runs at native speed with instant startup
• Includes command line tools like bash and git
• Free and open source

A serverless Linux environment running in the browser, client-side

Live demo · Repository

• Built on CheerpX, our x86 virtualization engine
• Run a full Linux userspace, terminal and tools included
• Full in-browser networking support through Tailscale
• Supports custom images
• Claude Computer Use support
• A complete Linux desktop environment in WebVM 2.0

A WebAssembly-powered x86 virtual machine for the browser

Website · Repository · Documentation

• Execute unmodified x86 binaries from JavaScript 🤯
• Safe sandboxed execution fully client-side
• Includes a x86-to-WebAssembly JIT compiler, a virtual block-based file system, and a Linux syscall emulator
• The engine behind WebVM
• CheerpX for Flash: See Flash content in modern browsers by running Flash Player via CheerpX

A Java Virtual Machine and runtime for the browser, backed by WebAssembly

Website · Repository · Documentation

• 100% compatible with Java 8
• Full runtime environment for applications, applets, libraries, and Java Web Start / JNLP applications
• Run any Java library from JavaScript using only its JAR file
• Java-JavaScript interoperability
• Swing and AWT Support
• Compile and run Java in the browser

An open-source C/C++ compiler that emits WebAssembly and JavaScript

Website · Repository · Documentation

• Port C/C++ libraries to the browser for use in JavaScript
• Write your web application in high-performance C++
• Emits best-optimised output without external tooling
• Stays up-to-date with LLVM/Clang upstream