Build Status


A node.js module for parsing form data, especially file uploads.

Current status

This module was developed for Transloadit, a service focused on uploading and encoding images and videos. It has been battle-tested against hundreds of GB of file uploads from a large variety of clients and is considered production-ready.


  • Fast (~500mb/sec), non-buffering multipart parser
  • Automatically writing file uploads to disk
  • Low memory footprint
  • Graceful error handling
  • Very high test coverage



  • Emit progress when content length header parsed (Tim Kosch├╝tzki)
  • Fix Readme syntax due to GitHub changes (goob)
  • Replace references to old 'sys' module in Readme with 'util' (Peter Sugihara)


  • Strip potentially unsafe characters when using keepExtensions: true.
  • Switch to utest / urun for testing
  • Add travis build


  • Remove file from package that was causing problems when installing on windows. (#102)
  • Fix typos in Readme (Jason Davies).


  • Do not default to the default to the field name for file uploads where filename="".


  • Support filename="" in multipart parts
  • Explain unexpected end() errors in parser better

Note: Starting with this version, formidable emits 'file' events for empty file input fields. Previously those were incorrectly emitted as regular file input fields with value = "".


  • Detect a good default tmp directory regardless of platform. (#88)


  • Fix problems with utf8 characters (#84) / semicolons in filenames (#58)
  • Small performance improvements
  • New test suite and fixture system


  • Exclude node_modules folder from git
  • Implement new 'aborted' event
  • Fix files in example folder to work with recent node versions
  • Make gently a devDependency

See Commits


  • Fix package.json to refer to proper main directory. (#68, Dean Landolt)

See Commits


  • Add support for multipart boundaries that are quoted strings. (Jeff Craig)

This marks the beginning of development on version 2.0 which will include several architectural improvements.

See Commits


  • Emit 'progress' event when receiving data, regardless of parsing it. (Tim Kosch├╝tzki)
  • Use W3C FileAPI Draft properties for File class

Important: The old property names of the File class will be removed in a future release.

See Commits

Older releases

These releases were done before starting to maintain the above Changelog:


Via npm:

npm install formidable@latest


git clone git:// formidable
vim my.js
# var formidable = require('./formidable');

Note: Formidable requires gently to run the unit tests, but you won't need it for just using the library.


Parse an incoming file upload.

var formidable = require('formidable'),
    http = require('http'),

    util = require('util');

http.createServer(function(req, res) {
  if (req.url == '/upload' && req.method.toLowerCase() == 'post') {
    // parse a file upload
    var form = new formidable.IncomingForm();
    form.parse(req, function(err, fields, files) {
      res.writeHead(200, {'content-type': 'text/plain'});
      res.write('received upload:\n\n');
      res.end(util.inspect({fields: fields, files: files}));

  // show a file upload form
  res.writeHead(200, {'content-type': 'text/html'});
    '<form action="/upload" enctype="multipart/form-data" method="post">'+
    '<input type="text" name="title"><br>'+
    '<input type="file" name="upload" multiple="multiple"><br>'+
    '<input type="submit" value="Upload">'+



new formidable.IncomingForm()

Creates a new incoming form.

incomingForm.encoding = 'utf-8'

The encoding to use for incoming form fields.

incomingForm.uploadDir = process.env.TMP || '/tmp' || process.cwd()

The directory for placing file uploads in. You can move them later on using fs.rename(). The default directory is picked at module load time depending on the first existing directory from those listed above.

incomingForm.keepExtensions = false

If you want the files written to incomingForm.uploadDir to include the extensions of the original files, set this property to true.


Either 'multipart' or 'urlencoded' depending on the incoming request.

incomingForm.maxFieldsSize = 2 1024 1024

Limits the amount of memory a field (not file) can allocate in bytes. If this value is exceeded, an 'error' event is emitted. The default size is 2MB.

incomingForm.hash = false

If you want checksums calculated for incoming files, set this to either 'sha1' or 'md5'.


The amount of bytes received for this form so far.


The expected number of bytes in this form.

incomingForm.parse(request, [cb])

Parses an incoming node.js request containing form data. If cb is provided, all fields an files are collected and passed to the callback:

incomingForm.parse(req, function(err, fields, files) {
  // ...


You may overwrite this method if you are interested in directly accessing the multipart stream. Doing so will disable any 'field' / 'file' events processing which would occur otherwise, making you fully responsible for handling the processing.

incomingForm.onPart = function(part) {
  part.addListener('data', function() {
    // ...

If you want to use formidable to only handle certain parts for you, you can do so:

incomingForm.onPart = function(part) {
  if (!part.filename) {
    // let formidable handle all non-file parts

Check the code in this method for further inspiration.

Event: 'progress' (bytesReceived, bytesExpected)

Emitted after each incoming chunk of data that has been parsed. Can be used to roll your own progress bar.

Event: 'field' (name, value)

Emitted whenever a field / value pair has been received.

Event: 'fileBegin' (name, file)

Emitted whenever a new file is detected in the upload stream. Use this even if you want to stream the file to somewhere else while buffering the upload on the file system.

Event: 'file' (name, file)

Emitted whenever a field / file pair has been received. file is an instance of File.

Event: 'error' (err)

Emitted when there is an error processing the incoming form. A request that experiences an error is automatically paused, you will have to manually call request.resume() if you want the request to continue firing 'data' events.

Event: 'aborted'

Emitted when the request was aborted by the user. Right now this can be due to a 'timeout' or 'close' event on the socket. In the future there will be a separate 'timeout' event (needs a change in the node core).

Event: 'end' ()

Emitted when the entire request has been received, and all contained files have finished flushing to disk. This is a great place for you to send your response.


file.size = 0

The size of the uploaded file in bytes. If the file is still being uploaded (see 'fileBegin' event), this property says how many bytes of the file have been written to disk yet.

file.path = null

The path this file is being written to. You can modify this in the 'fileBegin' event in case you are unhappy with the way formidable generates a temporary path for your files. = null

The name this file had according to the uploading client.

file.type = null

The mime type of this file, according to the uploading client.

file.lastModifiedDate = null

A date object (or null) containing the time this file was last written to. Mostly here for compatibility with the W3C File API Draft.

file.hash = null

If hash calculation was set, you can read the hex digest out of this var.


Formidable is licensed under the MIT license.