Remove Duplicates from Apple Photos Library on External Hard Drive

Duplicate Finder

Remove duplicate photos from local or external storage

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The Photos app on your Mac stores photos in a Photos library (with the extension .photoslibrary). If your library is too large to store on your Mac, you may consider storing it on an external storage device, such as an external hard drive.

In this article, I will show you how to use a duplicate file finder to easily and safely find and delete duplicates in a Photos library stored on an external hard drive.

Remove duplicates from an external Photos Library

Step 1. Connect the external hard drive containing your Photos library to your Mac.

Step 2. Press and hold the Option key and open the Photos app simultaneously, which will bring up the Choose Library dialog.

Step 3. Select the external library, then click Choose Library.

Step 4. In the Photos app, from the menu bar at the top of your screen, select Settings. In the General tab, click Use as System Photo Library. (If it is grayed out, it means that the library is already the system photo library.)

Step 5. Download and install Cisdem Duplicate Finder. Open this app.

Free Download macOS 10.11 or later

Step 6. Drag the external Photos library into the app. Click Scan.

Step 7. Once this Photos Library photoslibrary duplicate finder finishes scanning, a results window will appear, listing duplicate photos under the Images tab.

There are three view modes available. The first (default) one provides side-by-side previews, allowing you easily compare photos.

Step 8. In each group, the duplicate(s) will be automatically selected for deletion by the app’s Auto-Select feature, and one photo will stay unselected and untouched.

In addition, there are selection rules available for bulk selecting duplicates.

Step 9. Click Delete in the bottom right corner, then click Delete in the message that appears.

Now all selected files are moved to the Recently Deleted album in your Photos app.

Step 10. Optionally, select those deleted duplicates in Recently Deleted and click Delete Photos in the top right corner, which will permanently delete duplicates and free up space immediately.

Now the duplicates in your Photos Library are gone for good, which will instantly free up space on your external drive.

It’s very important to follow the steps and don’t skip any if you want to successfully delete duplicates from Apple Photo Library located on external drive. The guide above is also useful if you want to delete duplicates in a Photos Library located on your Mac.

How to move or copy Apple Photos Library to external drive

If your Photos Library is too large, you can move it to an external hard drive to save storage space on your Mac. It’s also possible to transfer it to devices like memory cards and USB flash drives, which is however not recommended by Apple. You can also copy the library to an external storage device for backup.

Step 1. If Photos is open, quit it first.

Step 2. Connect your external hard drive to Mac. In Finder, open the drive.

Step 3. Control-click Finder and select New Finder Window. Locate your library. Where is Photos Library on Mac? By default, it's /Users/(username)/Pictures.

Step 4. Drag the .photoslibrary file to your external drive. To copy the library for backup, just copy and paste the file instead.

If it fails to move, control-click your external drive's icon in Finder, select Get Info > Sharing & Permissions, and change the settings.

Conclusion

If you have problems deleting duplicates from the external Photos library, it may be that you haven't set it as the System Photo Library. Regardless of the location of the library, it’s recommended to find and delete duplicates in it regularly, which will help save space and better manage your photos.