Abstract--In contrast to conventional multi-page Web applications, an Ajax application is developed as a single-page application in which content and structure are changed at runtime according to user interactions, asynchronous messages received from the server and the current state of the application. These features make Ajax applications quite hard to understand for programmers. In this paper, we summarize an approach for supporting Ajax comprehension by recovering GUI-based state models of Ajax applications. Furthermore, we present a case study in which the model recovery approach has been assessed in terms of under and over approximation. Keywords-Reverse Engineering, Ajax, Finite State Machine.