`@fastify/multipart`

Parses multipart/form-data requests for file uploads.

Since Fastify 5 Spec ↗

Syntax

app.register(multipart, { limits? })

Parameters

Name	Type	Required	Description
`options`	`object`	No	Options like limits (fileSize, files) and attachFieldsToBody.

Returns

Promise<void> — Resolves when the plugin is registered.

Examples

import Fastify from 'fastify';
import multipart from '@fastify/multipart';
import { pipeline } from 'node:stream/promises';
import { createWriteStream } from 'node:fs';

const app = Fastify();
await app.register(multipart, { limits: { fileSize: 5_000_000 } });

app.post('/upload', async (req, reply) => {
  const file = await req.file();
  await pipeline(file.file, createWriteStream(`/tmp/${file.filename}`));
  return { uploaded: file.filename };
});

Notes

Stream files with req.file()/req.files() to avoid buffering large uploads in memory. Always set `limits.fileSize` to guard against abuse. Use attachFieldsToBody to access fields alongside a schema.