What is the difference between Node.js and browser-side JavaScript?

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Accepted Answer

Both run JavaScript on the V8 engine , but they operate in completely different environments with different APIs and purposes. 1. Environment Browser — runs in a sandboxed browser tab, for client-side UI. Node.js — runs on the server or local machine, for backend and system-level tasks. 2. Global object Browser — window (and document , navigator ). Node.js — global (and process , Buffer ). 3. APIs available Browser — DOM, fetch , localStorage , alert , Web APIs. Node.js — fs , http , crypto , os , child_process , stream — no DOM. 4. Module system Browser — ES Modules ( import/export ) natively. Node.js — supports both CommonJS ( require ) and ES Modules . 5. Security model Browser — sandboxed, restricted (same-origin policy, no file system access). Node.js — full access to the OS, filesystem, and network. Structure your answer around three axes: available APIs (DOM vs file system), security model (sandboxed vs full system access), and module systems. This shows a systematic understanding.