I think you might be able to simplify that to: Ext.Msg.wait('Loading...'); wait() will handle a lot of this config automatically for you. I typically only use the convenience methods of Ext.MessageBox like alert() or wait(). If I want to make any other sort of window, I'd typically do directly to an Ext Window. My guess is animEl is an element that should be used to animate showing the window (it looks like it grows from that element).