Online JS Compiler – Run JavaScript instantly in your browser without setup

Summary: Online JS Compiler is a free, browser-based JavaScript playground that enables writing, debugging, and executing code with real-time console output. It operates entirely client-side with no installation, login, ads, or tracking, providing a fast and privacy-focused environment.

What it does

It offers a sandboxed JavaScript editor powered by CodeMirror with syntax highlighting, auto-closing brackets, and theme toggling. Code runs instantly using Web Workers with infinite loop protection, supports file upload/download, auto-saves to LocalStorage, and shares code via Base64-encoded URLs.

Who it's for

Designed for developers, students, educators, and anyone needing quick JavaScript testing, debugging, prototyping, or code sharing across devices.

Why it matters

It solves issues of slow, ad-filled, or login-required editors by providing a lightweight, offline-capable, privacy-first platform that loads in under one second and requires no backend.