How can I consolidate photos from multiple drives onto a NAS and remove duplicates on macOS?

A simple approach is to first gather everything into one temporary location, even if that means bringing along duplicates. That gives you one complete pool to sort through instead of chasing files across several devices.

On macOS, if some images are inside the Photos library, you can copy/export the originals out first so they’re part of the same file-based collection. Then run a duplicate finder to remove obvious duplicate photos. One answer mentioned using Photos Duplicate Cleaner for this. Be aware you may still need to handle duplicate RAW files manually.

After that, import the consolidated files into a folder-based manager rather than relying on a library that hides files. One suggested Picasa because it works directly with normal folders. Then reorganize the photos into a clear folder structure such as year/month.

Once the library looks right, copy the organized collection to the NAS.

Important: keep your original drives untouched until you’ve verified the NAS copy and your duplicate cleanup. Also make sure the NAS is backed up—consolidation is not the same as backup.