Due to plain carelessness (and importing photos from various USB drives and External Hard Drives) my photo library in Photos on my Mac (and in iCloud) contains more than 36,000 photos. I am guessing that probably 25 percent of these are duplicates (excluding RAW and JPEG copies of the same file). Before the Photos App, I tried to eliminate duplicates on iPhotos using PhotoSweeper, but I ended up wiping out too many photos that were not duplicates but were similar files. I have read positive reviews of Duplicate Photos Fixer Pro, which some observers think causes fewer problems than PhotoSweeper. Can anyone suggest which program, or other progress, is best for eliminating duplicates. As a safety precaution, after identifying duplicates, I also want to be able to copy or move the trashed duplicates to an external hard drive. PhotoSweeper did not support this ability when I last used it.