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What is the difference between readFile and createReadStream in Node.js?

Q: What is the difference between readFile and createReadStream in Node.js?

**TL;DR.** fs.readFile reads the **whole file into memory** and gives you one Buffer/string when done — simple, but memory grows with file size. fs.createReadStream returns a **Readable stream** that emits the file in chunks, using constant memory and letting you start processing before the file is fully read. readFile 1 callback, whole file memory = file size simple, small files

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Explain how these two file reading approaches handle system memory and data processing differently.

file-systemstreamsmemory

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import { readFile, createReadStream } from 'node:fs';

// Whole file in memory — fine for a small config
const cfg = await import('node:fs/promises').then(f => f.readFile('config.json', 'utf8'));

// Stream a large file straight to the response — constant memory
app.get('/video', (req, res) => createReadStream('movie.mp4').pipe(res));

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