I'm using jQuery File Upload library (http://github.com/blueimp/jQuery-File-Upload), and I've been stuck figuring out how to use the library satisfying the following conditions. The page has multiple file input fields surrounded by a form tag. Users can attach multiple files to each input field All files are sent to a server when the button is clicked, not when files are attached to the input fields. Upload is done asynchronously Say the page has 3 input fields with their name attributes being "file1[]", "file2[]" and "file3[]", the request payload should be like {file1: [ array of files on file1[] ], file2: [ array of files on file2[] ], ...} Here's jsFiddle, it's behaving weird so far in that it sends post request twice and the first one is cancelled. http://jsfiddle.net/BAQtG/24/ The core part of js code looks like this. $(document).ready(function(){ var filesList = [] var elem = $("form") file_upload = elem.fileupload({ formData:{extra:1}, autoUpload: false, fileInput: $("input:file"), }).on("fileuploadadd", function(e, data){ filesList.push(data.files[0]) }); $("button").click(function(){ file_upload.fileupload('send', {files:filesList} ) }) }) Anybody have idea how to get this to work? Updates Now thanks to @CBroe 's comment, the issue that request is sent twice is fixed. However the keys of request parameter is not correctly set. Here's updated jsFiddle. http://jsfiddle.net/BAQtG/27/