I recently noticed that my Photos is taking a large amount of storage space on my hard drive. I enabled iCloud Photos, and the upload looks to be complete, but the size of the library has not decreased.

This library initially appeared on my Mac when I imported photos from my phone using a lighting cable as a way to back them up. The iCloud sync doesn't seem to have created duplicates, so I think it was able to detect that these are the same photos, but it's still taking a lot of space on my drive.

Is this expected? If not, what can I do to troubleshoot this?

In my preferences, Photos is set to "Optimize Mac storage".

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1 Answer 1


This is likely a combination of 2 things:

  • Recent files … are always on your Mac.

  • … optimised versions of your photos are always on your Mac.


iCloud Photo Library always keeps low resolution thumbnails of your photos locally, and will also keep new, recently viewed or edited photos cached locally as space permits. The latter is purgeable by macOS when necessary, but only when necessary, so if you've turned on iCloud Photo Library from having all your photos locally, macOS doesn't go out of its way to clear that space unless it needs that space for something else.

  • Ah, that's a bother. So there's no way to ask macOS to free up space?
    – kettlepot
    Commented Jun 4, 2021 at 20:47
  • If macOS has marked the space as purgeable, you shouldn't have to worry about it — macOS won't let the disk completely fill before purging. You can apparently force it by creating large files though. I don't know when macOS marks a recent file as no longer recent and therefore the space as purgeable.
    – grg
    Commented Jun 4, 2021 at 20:49
  • I see 241gb is purgeable, looks like a similar size to the library itself. Maybe that's it.
    – kettlepot
    Commented Jun 4, 2021 at 20:51
  • How are you backing up your photos? If you were to cause the Mac to throw off all Photos data, then you would have no backup. iCloud Photos is a sync service, not a backup service. Commented Jun 5, 2021 at 19:57
  • @Marc I think that is moot. As you say iCloud Photo Library is not a backup, causing the Mac to discard the local cache of images does not cause them to have no backup since they had no backup in the first place.
    – grg
    Commented Jun 5, 2021 at 20:17

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