EVALUATION OF INTERACTIONS WITH A USER INTERFACE

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for evaluating interactions with a user interface are disclosed. In one aspect, a method includes identifying a set of mutation events specifying changes to the structure of a user interface that occurred during the user session, and generating user interface states specifying different structures of the user interface throughout the given user session. Based at least in part on the user interface states, playback data that present visual changes of the user interface corresponding to the set of mutation events that occurred during the user session are generated. Session activity data describing user interactions that occurred during the user session are also generated. At least a portion of the playback data and the session activity data are output to a requesting device.