Abstract: A method and system for automatically determining the differences in a mobile device user interface throughout a development cycle. A test automation is run to exercise a target device's user interface. While the user interface is exercised, an extension is activated that takes snapshots of the user interface output at selected intervals of an automation execution. The snapshots are stored and uploaded to a server where snapshots of different automation executions are then compared on a pixel-by-pixel basis. The differences between snapshots are output in a visual format where the pixels that are different between snapshots are highlighted. The visual format of the differences between snapshots provides the user with a method to readily determine if errors exist in the user interface of the target device.