How do I set up automatic, incremental backup for my macOS Photos.app library?

Solution 1:

Backblaze might be a good option to mirror your entire Photos library. A 450MB overhead for a 90GB library isn't much; you'll need the database to fully restore your Photos Library i.e. albums, non-destructive edits etc. If you really want to backup just the original unmodified versions of photos and don't mind losing the organization and edits, you could backup only the Originals folder within the Photos Library.photoslibrary bundle.

Also, which version of macOS do you use? If Big Sur or Catalina, Photos Takeout may help you. This app exports photos and videos from Mac Photos in year or album-wise folders, and works with Photos for Sierra and later, but the feature to export incrementally is only available in Big Sur and Catalina (I work for App Initio Limited, the app developer, but for technical guidance you can contact our support team through the app).