The player apps record the viewer’s gaze four times a second. After the viewer finishes watching a video this gaze data is sent back to our servers and aggregated into a heatmap. Heatmaps are made of millions of gaze points which are constantly updated. The Heatmap Viewer visualizes this data by superimposing this data on the video to see how the gazes are distributed over time. The red areas of the heatmap indicate the areas with the most gazes.