A method, media, and systems for performing incremental visual comparison of web browser screens are provided. Structured representations of a current state of an event-driven application are accessed, one with respect to a plurality of client-tier environments. Where the current state is not an initial state of the event-driven application, structured representations of a prior state of the event-driven application are accessed, with respect to each client-tier environment. A set of one or more pairwise equivalences between the current state and the prior state of the event-driven application are determined with respect to each client-tier environment. A set of one or more matched portions between the first and second sets of pairwise equivalences is determined. Finally, one or more differences in a first end-user experience in the first client-tier environment are determined with respect to a second end-user experience in the second client-tier environment.