Multer
Node.js middleware that handles file uploads sent as multipart/form-data.
- Stars
- 12.1k
- Forks
- 1.2k
- Licence
- MIT
- Language
- JavaScript
- Last update
- 4 days ago
- Type
- Library
What it is
Multer is a middleware for Node.js servers that receives files and text fields sent from HTML forms. Web forms that upload files use the multipart/form-data format, and Multer parses that data so your server code can read the uploaded files and form values. It is built on top of busboy, a parser library, and it is commonly used with Express.
- Accept a profile picture on a /profile route with upload.single('avatar')
- Accept several gallery photos with upload.array('photos', 12)
- Accept multiple named file fields in one form with upload.fields()
- Accept text-only forms with upload.none() while rejecting unexpected files
Great for
- Node.js developers adding file upload to an Express app
- Developers who need to accept single or multiple files per form field
- Teams that want uploaded files saved to disk or kept in memory
- Developers who want control over how uploaded files are named and stored
Not ideal for
- Projects not using Node.js, since this is a JavaScript middleware
- Apps that only accept non-multipart requests, because Multer does not process any form that is not multipart/form-data
- Developers who want Multer applied globally, since the README warns that global use lets users upload files to routes you did not anticipate
How to get it
- 1
Install with a package manager
You'll need: Node.js · npm
Install Multer from npm
npm install multer - 2
Run it
- Install Multer with npm install multer.
- Add enctype="multipart/form-data" to your HTML form.
- Create an upload instance with multer({ dest: 'uploads/' }).
- Add upload.single('fieldname') or another method to your POST route and read req.file or req.files.
- 3
Get the most out of it
- Use the storage option with DiskStorage to control destination and filename, as shown in the README.
- Use fileFilter to control which files are accepted.
- Use limits.files and maxCount to bound how many files are accepted.
- Use preservePath only if you need client folder paths, and validate file.originalname before using it.
- Review the examples/ folder for browser FormData upload examples.
Downloads
Strengths
- Simple, short setup: install from npm and add it as route middleware
- Supports single, array, multi-field, and text-only upload patterns
- Lets you choose between disk storage, memory storage, or a custom storage engine
Trade-offs
- The README says file.originalname is client-supplied and must be validated, so safe handling is your responsibility
- Files are stored in memory by default if no dest or storage is set, which the README describes but which may matter for large uploads
- Only works for multipart requests; other body formats are not handled
Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.