The best app for this I have found

I’ve tried quite a few apps to find and eliminate duplicate photos, and this is by far the best. Excellent ability to recognize duplicates, which can easily be fine-tuned. Excellent ability to automatically select which photos to keep, based on many different criteria, which can be customized and prioritized. This is the one to get, in my opinion!

SDorst about PhotoSweeper, v2.2.6