apple photos app

But you should check all suggested duplicates before you merge them summarily or you might lose photos.

• Occasionally the suggested duplicates are no duplicates at all and are just having the same filename and a similar capture date.
• Occasionally the suggested duplicates are looking similar, but are different photos of the same scene. Then you may want to decide yourself, which photo is the better shot, as it is a matter of artistic taste.
• Photos will flag photos as duplicates, even when I created the duplicate myself, because I needed two differently edited versions of the same photo.
• And if the two duplicates are having different metadata, different capture dates or different locations, only you can know, which date or location are the correct ones and should be kept.

Click on the Duplicates folder and type ⌘+A to select all. Then use the Merge menu option.