Deno JavaScript Runtime

Deno is a free and open-source modern, secure runtime for JavaScript, TypeScript, and WebAssembly, created by Ryan Dahl (the original creator of Node.js in 2009) in 2018 (first publicly released as version 1.0 in May 2020) as a response to the design regrets he identified with Node.js. Developed by the Deno Land Company, Deno addresses Node.js's security model, module system, and build tooling issues. Key features: secure by default: Deno runs scripts with no file system, network, or environment access unless explicitly granted via command-line flags (--allow-read, --allow-write, --allow-net, --allow-env, --allow-run). This permission model prevents supply-chain attacks from accessing sensitive resources. TypeScript native: Deno has a built-in TypeScript compiler, so TypeScript files can be executed directly without ts-node, tsc, or any configuration. Standard library: a curated standard library (deno.land/std) covering common needs like HTTP servers, file I/O, datetime, crypto, testing, and more — similar to Go's standard library. URL-based imports: modules are imported via URLs (import { serve } from 'https://deno.land/std/http/server.ts') instead of npm packages, eliminating the need for package.json and node_modules. Deno caches downloaded modules locally for offline use. Web API compliance: implements standard Web APIs (fetch, WebSocket, Workers, AbortController, Streams, URL, crypto.subtle) instead of custom Node.js APIs. ES Modules: uses ECMAScript modules exclusively (import/export), no CommonJS (require/module.exports). Top-level await: await can be used at the top level without wrapping in async functions. Built-in tooling: code formatter (deno fmt), linter (deno lint), test runner (deno test), bundler (deno bundle), dependency inspector (deno info). V8 engine (same as Chrome and Node.js). Tokio async runtime (Rust). Built in Rust. MIT.