Called when popup is opened or transitions to the new content. This event is triggered when popup is first opened and any time .open or .load methods are called. There can be only one popup window on the screen at any given time. If you call .open method again, the popup will transition into new content. You can add event listener during the object creation: w2popup.open({ title : 'Title', body : 'Body', onOpen : function (event) { console.log('event: ' + event.type, event); } }); or after popup is opened: w2popup.on('open', function(event) { console.log('event: ' + event.type, 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. See events page in utilities for more details.