Do you use iCloud Drive to store your files? Are you intending to upgrade to Sonoma?

If the answer to both questions is yes, then you might benefit from spending a couple of minutes reading this article and following its advice. The reason is that Sonoma fixes a long-standing bug in whether local files can be ‘evicted’ to iCloud, or the download removed from your Mac’s local storage. In some circumstances you could find Sonoma downloading everything you have removed from your local storage, which may come as a surprise.

Checks

Your first check is in System Settings, in [Apple ID] > iCloud, where you inspect the setting you have for Optimise Mac Storage. If that’s turned on, then you need read no further, as your iCloud files can be stored locally or just in iCloud, and you and macOS manage that by evicting them from your Mac when necessary.

If that setting is turned off, as shown above, then you need to make a further check in your iCloud Drive in the Finder. If all the files and folders look normal and don’t have any characteristic cloud icon with a downward pointing arrow, then it means that all those are already downloaded and stored locally, as well as in iCloud. There are no surprises in store for you, in this respect, when you upgrade to Sonoma.

If your Mac has Optimise Mac Storage turned off but has files or folders in iCloud Drive bearing that distinctive icon, then it means that all those files and folders are likely to be downloaded to your Mac’s local storage as soon as it’s upgraded to Sonoma. You therefore need to consider whether this might cause your Mac to run low on free disk space, and plan accordingly.

If your Mac has Optimise Mac Storage turned on, then you don’t need to do anything, as Sonoma should continue to manage eviction as it has done previously.

Here’s the full explanation.

iCloud and local storage

Files stored in iCloud exist in one of three states:

1. A full copy of the file is in your Mac’s local storage, and another is in iCloud’s servers. When you look at the file in the Finder, it has no iCloud icon by it (or an icon showing just the cloud without an arrow), and its status is downloaded.
2. There is no full copy of the file on your Mac’s local storage (there’s actually a hidden placemarker or stub file there instead), but it’s in iCloud’s servers, and possibly stored locally on other Macs or devices. When you look at the file in the Finder, it has an iCloud icon with an arrow pointing down. Its status is evicted, as it has been evicted from local storage.
3. The intermediate between those two states, in which a file is being downloaded from iCloud to provide a copy on your Mac’s local storage. This may be marked by an icon showing just the cloud (without an arrow) together with the downloading progress circle, and its status is downloading.

Optimise Mac Storage

Behaviour of iCloud depends on two key settings in iCloud settings: whether iCloud Drive is also enabled for Desktop & Documents Folders (something I won’t go into further here), and whether Optimize Mac Storage is enabled.

If Optimize Mac Storage is not enabled, then all files in iCloud Drive should either be downloaded or downloading, as without that storage optimisation, all files should be stored locally.

If Optimize Mac Storage is enabled, then files can be evicted by macOS, to save space on your local Mac storage, or you can manually evict files using my free apps Cirrus and Bailiff, or using the Remove Download command in the Finder’s contextual menu.

Until the release of macOS Sonoma 14.0, there has been a bug in the Optimize Mac Storage setting, that has allowed eviction of iCloud files from local storage when that setting is off, and many of us have come to accept that we can still use that feature, even though it shouldn’t have worked.

The good news is that Sonoma fixes that bug. But if you’re still relying on iCloud keeping some or many of your files evicted, and Optimize Mac Storage is off, when you upgrade to Sonoma all those evicted files will be downloaded to your Mac, as they should have been all along. If you then try evicting them using Cirrus or Bailiff, the app will return an error.

The choice

If you’re happy that your Mac has sufficient free space on its boot disk to accommodate those files when they’re downloaded, and you want them stored locally, then leave Optimize Mac Storage set off, and that’s what you’ll get. This has the advantage that all those files can be backed up locally, and will be included in Spotlight search.

If you’re concerned that your Mac won’t have sufficient local storage to accommodate them all at once, then before upgrading to Sonoma set Optimize Mac Storage to on, and Sonoma should leave them where they are (and aren’t). You’ll then be able to continue to evict files when you want, but so will macOS. Evicted files aren’t backed up locally, and are excluded from Spotlight search too.