@krzykat said in Photo Backup And Sharing:

Also - get rid of the duplicates of different sizes, such as when you send a photo over your phone to a friend, it makes a copy that is resized.

That's not a dupe, but a cache. Typically you want those kept so that it doesn't have to recalculate each time. But not always. But that would be a different database mechanism rather than a dupe finder.