Node Streams

Streams are one of the most powerful and efficient features in Node.js.

They allow you to work with data piece by piece, rather than loading entire files or responses into memory. This makes streams ideal for handling large datasets, file operations, and network communication.

Why streams matter

Streams help you:

process large files without memory issues
improve performance for I/O‑heavy tasks
handle data as it arrives (e.g., from a network request)
build efficient pipelines for transforming data

They are a core part of Node’s design and are used internally by many APIs.

Types of streams

Node.js provides four main types of streams:

Readable – you read data from them
Writable – you write data to them
Duplex – both readable and writable
Transform – duplex streams that modify data as it passes through

Examples include file streams, HTTP request/response objects, and compression utilities.

Basic example

import fs from "node:fs";

const readable = fs.createReadStream("input.txt");
const writable = fs.createWriteStream("output.txt");

readable.pipe(writable);

console.log("File copied using streams");