This can save you invaluable disk space not just on your Mac but even on any external storage device.

All copies of a photo are deleted except the original one. Photos Duplicate Cleaner creates groups of duplicate photos so that it is easy to find out the number of occurrences of similar photos and clean selected duplicates. As a result, you’ll save ample of space on your Mac. Instead of searching your Mac manually for duplicates, select a particular folder and let this cleaner do its work. Photos Duplicate Cleaner minimizes the tedious efforts used for searching your entire system for duplicate photos.