Ext dialogs and message boxes have similar functionality as the Wt dialogs. MessageBox contains text messages, while Dialog can contain any content. A progress dialog is a dialog containing a progress bar.

The progress bar example occupies a session thread, while the dialog and the message box don't. This is a programming style difference that is invisible to the users of the application. As with Wt's dialogs, both can be used in the mode of your choice, though it is usually required not to lock up session threads.