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How do you handle streaming multipart file uploads (busboy/multer)?

Q: How do you handle streaming multipart file uploads (busboy/multer)?

**TL;DR.** Don't buffer uploads in memory — **stream** them. busboy (which multer wraps) parses the multipart/form-data request and emits **each file as a stream** you pipe straight to disk or object storage. This keeps memory flat for large files and lets you enforce size limits **mid-stream**. multipart req fields + files busboy file stream <path class='d-ed

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Understand the problem

Parsing multipart/form-data without buffering whole files in memory.

nodejsuploadsstreamsmultipart

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Read the code

Stream a file part to disk with busboy

import Busboy from 'busboy';
import { createWriteStream } from 'node:fs';
import { pipeline } from 'node:stream/promises';

app.post('/upload', (req, res) => {
  const bb = Busboy({ headers: req.headers, limits: { fileSize: 50e6 } });
  bb.on('file', async (name, file, info) => {
    await pipeline(file, createWriteStream('/uploads/' + info.filename));
  });
  bb.on('close', () => res.json({ ok: true }));
  req.pipe(bb);
});

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