How do I store my iCloud library on an external drive?

One common issue using iCloud Photos on your Mac is when the amount of data you have in iCloud Photos is too much for the internal drive on your Mac to hold all at once. Photo does include the “Optimize Mac Storage” setting, which will tell Photos not to download the full size copy of a photo until it’s specifically viewed in full size in the Photos app. This is convenient, but has a major downside: because you no longer have local copies of all your photos, any local backups that are made of your library will not contain all of your photos.

One solution for this problem is to move your iCloud library to an external drive that does have enough free space to hold all your photos. That way, you know all your photos are locally available and will be backed up by Time Machine or whatever other backup software you use on your Mac.

Creating the new library

If you already have iCloud Photos enabled on your Mac, here is how to move your library to an external drive.

1. Open PowerPhoto and select your iCloud library. PowerPhotos will display an “iCloud Photos” label below the library that is currently syncing with iCloud Photos. If you don’t see such a label under any of your libraries, then you don’t have iCloud Photos enabled - refer to the “If you don’t have iCloud Photos enabled” section below instead.
2. Choose File > Duplicate Library, then choose the folder on your external drive where you’d like to store your library. You may also want to give it a distinctive name like “iCloud Photo Library” or “External Library”. See Storing a library on an external drive for information on compatible external drives.

If you don’t have iCloud Photos enabled, then instead of copying your existing library, you’ll create a new library instead.

1. Open PowerPhotos and choose File > New Library from the menu bar.
2. Choose the folder on your external drive where you’d like to store the new library. You may want to give it a distinctive name like “iCloud Photo Library” or “External Library”.

Switching iCloud Photos

Now that you have your library on the external drive, it’s time to switch iCloud Photos to sync with that library.

1. Once you’ve copied/created your library, you should see the new library at the bottom of the PowerPhotos library list. Double click on the library to open it in Photos.
2. Open the Settings window and go to the General section, then click on the button labelled “Use as System Photo Library”. This will disable iCloud Photos on the library on your internal drive, and switch your external library to be the new system photo library.
3. Finally, click on the “iCloud” section in the Settings window and check the “iCloud Photos” checkbox to enable iCloud Photos on your external library. Assuming you want local copies of all the photos, make sure to choose the “Download Originals” option instead of “Optimize Mac Storage”.
4. The initial sync with iCloud Photos will likely take a while. It will start by comparing the content of the local library with what’s in iCloud, then it will proceed to download any remaining images that weren’t already downloaded. You can check its progress by selecting the main “Library” album at the top of the album list in Photos, which shows all the photos in the library. Scroll all the way to the bottom of the photo browser, and there should be a status message saying how far along syncing with iCloud has proceeded.

Once you have your library setup, Photos will keep that copy of the library synced with iCloud Photos going forward. It’s safe to disconnect the external drive and reconnect it later - Photos will pick up syncing wherever it left off the last time the drive was connected. If you wish to switch back to using your internal library with iCloud Photos, repeat the “Switching iCloud Photos” steps, opening the internal library in Photos instead of the external library.