Simple express file upload middleware that wraps around Busboy

Usage no npm install needed!

<script type="module">
  import expressFileupload from '';



Simple express middleware for uploading files.

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Security Notice

Please install version 1.1.10+ of this package to avoid a security vulnerability in Node/EJS related to JS prototype pollution. This vulnerability is only applicable if you have the parseNested option set to true (it is false by default).


# With NPM
npm i express-fileupload

# With Yarn
yarn add express-fileupload


When you upload a file, the file will be accessible from req.files.


  • You're uploading a file called car.jpg
  • Your input's name field is foo: <input name="foo" type="file" />
  • In your express server request, you can access your uploaded file from'/upload', function(req, res) {
  console.log(; // the uploaded file object

The object will contain the following:

  • "car.jpg"
  • A function to move the file elsewhere on your server. Can take a callback or return a promise.
  • The mimetype of your file
  • A buffer representation of your file, returns empty buffer in case useTempFiles option was set to true.
  • A path to the temporary file in case useTempFiles option was set to true.
  • A boolean that represents if the file is over the size limit
  • Uploaded size in bytes
  • MD5 checksum of the uploaded file

Notes about breaking changes with MD5 handling:

  • Before 1.0.0, md5 is an MD5 checksum of the uploaded file.
  • From 1.0.0 until 1.1.1, md5 is a function to compute an MD5 hash (Read about it here.).
  • From 1.1.1 onward, md5 is reverted back to MD5 checksum value and also added full MD5 support in case you are using temporary files.


Using Busboy Options

Pass in Busboy options directly to the express-fileupload middleware. Check out the Busboy documentation here.

  limits: { fileSize: 50 * 1024 * 1024 },

Using useTempFile Options

Use temp files instead of memory for managing the upload process.

// Note that this option available for versions 1.0.0 and newer. 
    useTempFiles : true,
    tempFileDir : '/tmp/'

Using debug option

You can set debug option to true to see some logging about upload process. In this case middleware uses console.log and adds Express-file-upload prefix for outputs.

It will show you whether the request is invalid and also common events triggered during upload. That can be really useful for troubleshooting and we recommend attaching debug output to each issue on Github.

Output example:

Express-file-upload: Temporary file path is /node/express-fileupload/test/temp/tmp-16-1570084843942
Express-file-upload: New upload started testFile->car.png, bytes:0
Express-file-upload: Uploading testFile->car.png, bytes:21232...
Express-file-upload: Uploading testFile->car.png, bytes:86768...
Express-file-upload: Upload timeout testFile->car.png, bytes:86768
Express-file-upload: Cleaning up temporary file /node/express-fileupload/test/temp/tmp-16-1570084843942...


  • Temporary file path is... says that useTempfiles was set to true and also shows you temp file name and path.
  • New upload started testFile->car.png says that new upload started with field testFile and file name car.png.
  • Uploading testFile->car.png, bytes:21232... shows current progress for each new data chunk.
  • Upload timeout means that no data came during uploadTimeout.
  • Cleaning up temporary file Here finaly we see cleaning up of the temporary file because of upload timeout reached.

Available Options

Pass in non-Busboy options directly to the middleware. These are express-fileupload specific options.

Option Acceptable Values Details
  • false (default)
  • true
Automatically creates the directory path specified in .mv(filePathName)
  • false (default)
  • true
Applies uri decoding to file names if set true.
  • false (default)
  • true
  • regex
Strips characters from the upload's filename. You can use custom regex to determine what to strip. If set to true, non-alphanumeric characters except dashes and underscores will be stripped. This option is off by default.

Example #1 (strip slashes from file names): app.use(fileUpload({ safeFileNames: /\\/g }))
Example #2: app.use(fileUpload({ safeFileNames: true }))
  • false (default)
  • true
  • Number
Preserves filename extension when using safeFileNames option. If set to true, will default to an extension length of 3. If set to Number, this will be the max allowable extension length. If an extension is smaller than the extension length, it remains untouched. If the extension is longer, it is shifted.

Example #1 (true):
app.use(fileUpload({ safeFileNames: true, preserveExtension: true }));
myFileName.ext --> myFileName.ext

Example #2 (max extension length 2, extension shifted):
app.use(fileUpload({ safeFileNames: true, preserveExtension: 2 }));
myFileName.ext --> myFileNamee.xt
  • false (default)
  • true
Returns a HTTP 413 when the file is bigger than the size limit if true. Otherwise, it will add a truncated = true to the resulting file structure.
  • 'File size limit has been reached' (default)
  • String
Response which will be send to client if file size limit exceeded when abortOnLimit set to true.
  • false (default)
  • function(req, res, next)
User defined limit handler which will be invoked if the file is bigger than configured limits.
  • false (default)
  • true
By default this module uploads files into RAM. Setting this option to True turns on using temporary files instead of utilising RAM. This avoids memory overflow issues when uploading large files or in case of uploading lots of files at same time.
  • String (path)
Path to store temporary files.
Used along with the useTempFiles option. By default this module uses 'tmp' folder in the current working directory.
You can use trailing slash, but it is not necessary.
  • false (default)
  • true
By default, req.body and req.files are flattened like this: {'name': 'John', 'hobbies[0]': 'Cinema', 'hobbies[1]': 'Bike'}

When this option is enabled they are parsed in order to be nested like this: {'name': 'John', 'hobbies': ['Cinema', 'Bike']}
  • false (default)
  • true
Turn on/off upload process logging. Can be useful for troubleshooting.
  • 60000 (default)
  • Integer
This defines how long to wait for data before aborting. Set to 0 if you want to turn off timeout checks.

Help Wanted

Looking for additional maintainers. Please contact richardgirges [ at ] if you're interested. Pull Requests are welcome!

Thanks & Credit

Brian White for his stellar work on the Busboy Package and the connect-busboy Package