PhotoSweeper - PhotoSweeper helps photographers get rid of tones similar photos on OS X.
Google Photos - All your photos are backed up safely, organized and labeled automatically, so you can find them fast, and share them how you like.
Powerphotos - PowerPhotos lets you organize your Photos libraries on the Mac. You can split a library into smaller ones, merge libraries together, find duplicate photos, and more.
Immich - immich Self-hosted photo and video backup solution directly from your mobile phone
MacPaw Gemini 2 - The intelligent duplicate file finder
Piwigo.org - Manage your photo collection with Piwigo. Piwigo is open source photo gallery software for the web. Designed for organisations, teams and individuals.