Eye gaze is an important source of information to evaluate computer interfaces. Typically, visualization of gaze data is performed using heatmaps and gaze scanpaths displayed on top of images of the interface, enhancing regions that have attracted the user’s visual attention. Such tools work well for static interfaces but they are not appropriate to visualize dynamic interfaces where the object of interaction is always changing, such as games, web browsing, or even common applications that change the interface according to the status of the application. In this paper we introduce an interactive tool to explore the spatial-temporal distribution of visual attention called Heatmap Explorer (HME). HME allows the experimenter to control the visualization by selecting temporal intervals and adjusting filter parameters of the eye movement classification algorithm. We show results of three typical application scenarios and discuss how HME can be an effective usability evaluation tool.