Virtual Filesystem
POSIX-compatible in-memory filesystem with watch, stat, and recursive operations.
Node.js Runtime
Execute JS/TS with 40+ shimmed modules — fs, path, http, crypto, streams, and more.
npm in the Browser
Install real npm packages, resolve dependencies, extract tarballs — all client-side.
Framework Dev Servers
Built-in Next.js and Vite dev servers with file-based routing and React support.
Hot Module Replacement
React Refresh, CSS Modules, and instant file updates without page reload.
Security Modes
Cross-origin sandbox, Web Worker isolation, or same-origin main thread execution.