How do I delete duplicate photos in Photos?

You want an app that will identify the potential duplicates, put them in an album or mark them with a keyword for easy retrieval and deletion by you. You don't want one that does the deletion itself for obvious reasons.

I've been able to run tests on the following apps:

PhotoSweeper - $9.99 - Demo version available.

PowerPhotos - $29.95

PowerPhotos is the iPhoto Library Manager version for Photos and is very powerful. Although more expensive I would recommend it as it has more capabilities than the others like the capability to merge Photos libraries or copy photos along with their metadata between libraries.

PhotoSweeper compares bitmaps and/or histograms so it can detect duplicate images even if they have different file sizes, file names, image sizes and capture dates.

Photos does not have a tool to search for duplicates, once they have been imported to Photos. Photos's strategy is to prevent you from importing duplicates. When you import photos, you will be alertetd, if you are about to imort a photo, that is already in your Photos Library. This will detect exact duplicates, if you import the same file twice. Photos does not detect different versions of the same photos as duplicates.

If you imported duplicates in spite of the warnings, you are on your own. Try to spot duplicates by sorting the photos by the capture date.Then exact duplicates should appear side-by-side.

How do I delete duplicate photos?

And how do I export photos to a file and not an album?