Excellent program - take time to learn to use it

This program is fantastic. Its default settings are very thoughtful — for example, it will keep the higher resolution if you have duplicate files that are different sizes. You can first look for exact matches and then gradually ratchet back to look for more and more differences, until you decide that the level of difference is at the point that they are not duplicates (to you). It turned out that most of my duplicates were actually 99.9% identical according to Photosweeper because they were different sizes (I had downloaded duplicates of 1000+ images over the years).

* Apple Photos (2015) *
It is possible to get in trouble deleting important photos. With the new Apple Photos app depending on your settings you may not have all of the original full resolution images on your laptop/desktop. I therefore recommend running Photosweeper only on a computer that has all of the full resolution images downloaded. If you see a lot of 0 KB images listed as duplicates, give Photos more time (days, perhaps) to download the images and then start to use Photosweeper.

mjm30 about PhotoSweeper