Here’s how to remove duplicates from your Apple Photo Library.
1. Download a free app called ‘Duplicate File Finder Remover’
Any app like this will do that finds duplicate files in the finder.
2. Find your Photos Library. It’s in your home user folder in a folder called ‘Pictures.’
Control-click on it and select ‘Show Package Contents.’ This will open the folder so you can see what is inside it. The photo’s library is actually just a folder.
Inside the photos library you should see a folder called ‘originals.’ This is the folder you will drag into the ‘Duplicate File Finder’ Application to search for duplicates.
Open the Duplicate File Finder app and drag the ‘originals’ folder into to. Press ‘Show results’ to search fro duplicates.
Here you can see that I had 1128 duplicates taking up 2.33 GB of data. Click ‘Review and Remove’ to remove them.