Called during the save request. This event is triggered during the save request. For the event to be triggered, the server must respond with a Content-Length header during the XMLHttpRequest upload progress event. You can add event listener during the object creation: let form = new w2form({ name : 'form', url : 'server/post', record: { field_1 : 1, field_2 : 2 }, fields: [ { field: 'field_1', type: 'text', required: true }, { field: 'field_2', type: 'alphanumeric', required: true } ], onProgress: function(event) { console.log(event); } }); or after the object has been created: w2ui.form.on('progress', function(event) { console.log(event); }); The event handler is called before the default action of the event is triggered. You can cancel the default action by calling event.preventDefault(). To perform an action after the event is fully processed, define event.onComplete function. Cancelling this event will prevent the progress overlay from being updated. See events page in utilities for more details.