What is Node.js?

What is Node.js?

Node.js is a JavaScript runtime built on Chrome's V8 engine. It lets you run JavaScript outside the browser — on a server, your local machine, or inside cloud functions. Released in 2009 by Ryan Dahl, Node.js made it possible to use one language — JavaScript — across the entire stack.

Node.js is single-threaded and uses a non-blocking I/O model driven by an event loop. This makes it exceptionally efficient for I/O-heavy workloads like APIs, file processing, and real-time applications, without the overhead of spawning threads for every request.

What Node.js is NOT

Node.js is not a web framework — it is a runtime. You still need libraries like Express or Fastify to build HTTP servers comfortably. It is also not multi-threaded by default; CPU-intensive tasks can block the event loop and hurt performance.

• Runtime: executes JavaScript server-side using V8
• Event-driven: uses callbacks and an event loop instead of threads
• Cross-platform: runs on Linux, macOS, and Windows
• Rich ecosystem: over 2 million packages on npm