The FormData() constructor creates a new FormData object.

Note: This feature is available in Web Workers.


var formData = new FormData(</code><code>form</code><code>)


form Optional
An HTML <form> element — when specified, the FormData object will be populated with the form's current keys/values using the name property of each element for the keys and their submitted value for the values. It will also encode file input content.


The following line creates an empty FormData object:

var formData = new FormData(); // Currently empty

You could add a key/value pair to this using FormData.append:

formData.append('username', 'Chris');

Or you can specify the optional form argument when creating the FormData object, to prepopulate it with values from the specified form:

<form id="myForm" name="myForm">
    <label for="username">Enter name:</label>
    <input type="text" id="username" name="username">
    <label for="useracc">Enter account number:</label>
    <input type="text" id="useracc" name="useracc">
    <label for="userfile">Upload file:</label>
    <input type="file" id="userfile" name="userfile">
<input type="submit" value="Submit!">

Note: All input elements have a 'name' attribute. It is necessary to be able to access their values later.

var myForm = document.getElementById('myForm');
formData = new FormData(myForm);


Specification Status Comment
The definition of 'FormData()' in that specification.
Living Standard Initial definition

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 7 4.0 (2.0) 10 12 5
append with filename (Yes) 22.0 (22.0) ? ? ?
available in web workers (Yes) 39.0 (39.0) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 3.0 ? 4.0 (2.0) ?


append with filename ? ? 22.0 (22.0) ? ? ?
Available in web workers ? ? 39.0 (39.0) ? ? ?


Note: XHR in Android 4.0 sends empty content for FormData with blob.

Gecko notes

Prior to Gecko 7.0 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4), if you specified a Blob as the data to append to the object, the filename reported in the "Content-Disposition" HTTP header was an empty string; this resulted in errors being reported by some servers. Starting in Gecko 7.0, the filename "blob" is sent.

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API Constructor FormData Reference XHR XMLHttpRequest