When building web applications for use on different devices, developers need to deal with a wide range of input/output capabilities that affect how users interact with the application: A dialog that can be completed in one step on a desktop client may have to be broken up into a number of steps on a small-screen mobile device. Since it is time-consuming to define all the possible dialog masks and dialog flow variants for different channels manually, it would be desirable to automate the adaptation of dialog masks and flows. To address this need, we introduce the DiaDef language for the abstract, device-independent definition of the widgets in a dialog, and the DiaGen framework that automatically breaks this abstract dialog definition down into sufficiently small dialog masks for the users’ mobile devices and incorporates them into suitable micro dialog flows that are generated at run-time in order to be handled by our Dialog Control Framework.