Comparing iOS Screenshots
Compare screenshots to detect subtle changes to your user interface.
Connect your device to your Mac.
In the Devices organizer, select Screenshots for a device or for the Library section.
Select two or more screenshots.
Select the Compare option.
Use the Tolerance slider to adjust the comparison threshold.
The screenshots you select must be the same size and at least somewhat similar. You cannot compare screenshots whose resolution or dimensions are different. For example, you cannot compare a screenshot taken on a Retina display with one taken on a lower-resolution display. If the content of the screenshots is completely different, the Compare option is not available.