Deno JavaScript Runtime

Deno is an open-source JavaScript, TypeScript, and WebAssembly runtime built in Rust that runs TypeScript files directly without a compilation step or configuration file. The runtime uses the V8 JavaScript engine, the same engine powering Google Chrome, wrapped in a Rust-based host that provides security, standard library modules, and a built-in toolchain. TypeScript support is native: a developer writes a .ts file and executes it with a single command, and the runtime handles transpilation, type checking, and module resolution automatically. A permission system prompts or denies access to network, file system, environment variables, system information, and high-resolution timers based on command-line flags, preventing supply-chain attacks from silently exfiltrating data or establishing network connections. The standard library provides audited utility modules for HTTP serving, file I/O, cryptographic hashing, data encoding, and testing, following web platform standards wherever possible. Fetch, WebSocket, Streams, Web Workers, and other browser-standard APIs are implemented natively, enabling code that works in both browser and server contexts without environment-specific imports. The runtime reads package.json files and resolves npm imports through the npm specifier syntax, maintaining backward compatibility with the Node.js ecosystem. Built-in tools include a test runner with code coverage, a code formatter, a linter, a dependency inspector, and a compile command that bundles a script into a standalone executable. The associated cloud platform deploys applications globally at the edge. Used by Slack, Netlify, GitHub, Supabase, Stripe, and Bank of America in production environments.