I want to use the Photos.app option "Optimize Mac Storage" to free up space on my Mac, rather than downloading my entire iCloud Photos Library to my small laptop SSD.

Is there any way to strictly limit the space given to the Photos library?

I want to give, say, 40 GB to Photos. The app can "optimize" that space as it sees fit, but I never want it to take more than 40 GB.

iCloud Photos > Optimize Mac Storage

If your Mac is low on space, full-resolution photos and videos are automatically replaced with smaller, device-sized versions. Full-resolution versions can be downloaded from iCloud anytime.

  • Can putting it on a new volume of limited size work? That's a very leap-y guess.
    – anki
    Commented Sep 28, 2019 at 6:27
  • I'm thinking to try that, the limited size volume, it logically makes sense
    – MDJCM
    Commented Jan 3, 2023 at 6:27
  • I'm now getting the error "Not Enough Local Storage" using the APFS solution.
    – pkamb
    Commented Apr 1, 2023 at 19:20

1 Answer 1


Limiting Photos iCloud Photos Library sizes was discussed on Accidental Tech Podcast:

They originally suggested using a Sparse Disk Image with a size quota.

Follow-up suggested instead using an APFS Space-Sharing volume.

Hey, others may have said this, but don’t use a sparse image for your photo library. Add an APFS volume with a 30GB quota instead. Much, much safer! (twitter)

APFS Space-Sharing Volume

In Disk Utility, select Add APFS Volume..

APFS volumes share storage space within their container.

Add APFS volume to container

Set a Quota Size to strictly limit the size of the new volume:

Size Options

APFS Volumes share storage space within their container. The optional reserve size ensures that amount of storage will remain available for this volume. The optional quota size limits how much storage this volume can allocate.

Set a Quota Size

When you move your Photos library, your iCloud photos will only be permitted to fill this Quota Size set for the volume.

Move Photos Library

Finally, move your Photos library file to the new size-limited volume.

Quit Photos.app > Move the library file > Hold Option and relaunch Photos > Pick the library’s new location > Photos Preferences > Use as System Photo Library

How to put Photos.app main library on an external disk?

Or, start a new Photos library on the volume and allow iCloud to re-download your photos.

  • what happens if you take like 10 new photos after partition is full?
    – Natsfan
    Commented Nov 24, 2019 at 20:29
  • @jmh probably what happens in iPhone. No more sync. Disk full.
    – anki
    Commented Dec 3, 2019 at 9:19
  • 2
    I've had trouble using APFS. After filling up about half of the image, Photos shows an error message saying that there isn't enough space. I'm moving to the original method with the sparse image outlined by Marco. Commented Jun 22, 2020 at 12:07
  • 1
    One thing I don't understand : if the Library file is let's say 60GB and you created the quota specifically to limit it to let's say 40GB... Then how is it possible to follow the last instructions : "Move the library file"? The library file is bigger than the new partition... Commented Jul 10, 2021 at 21:37
  • 2
    Heh. I just happened across the need to do this, and ATP immediately came to mind. I didn't want to go through the legwork of digging up when they talked about it, so I Googled instead, and this was the first result. Thank you very much.
    – Kye
    Commented Jan 24, 2023 at 1:15

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