< form method = "post" enctype = "multipart/form-data" > < div class = "form-group" > < label >Choose File:</ label > < input type = "file" id = "file" /> </ div > </ form > <script> var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>" ; jQuery( function ($) { $( 'body' ).on( 'change' , '#file' , function () { var file_data = $(this).prop( 'files' )[0]; var form_data = new FormData(); form_data.append( 'file' , file_data); ...