iCloud Drive taking up space on your Mac? Here is why

Why cloud files use local disk

iCloud Drive keeps a local copy of your files so they open instantly and work offline. On the Mac they are stored in a hidden folder, ~/Library/Mobile Documents, and Finder presents them as iCloud Drive in the sidebar.

If you turned on Desktop and Documents Folders in the iCloud Drive settings, those two folders are part of iCloud Drive too. That is convenient, but it means everything you save to the Desktop is uploaded and also kept locally, on every Mac that uses the setting.

See how much is stored locally

The icons in Finder tell you the state of each item. A cloud with a downward arrow means the file is in iCloud only and takes almost no local space. No icon means it is downloaded.

The command below adds up what iCloud Drive actually occupies on this Mac. Files that are in iCloud only count for almost nothing, so the result is the amount you could release. It only reads. macOS may ask whether Terminal can access your iCloud Drive files.

du -sh ~/Library/Mobile\ Documents 2>/dev/null

Turn on Optimize Mac Storage

Open System Settings, click your name at the top of the sidebar, then iCloud, then Drive, and turn on Optimize Mac Storage.

With this on, macOS keeps recent files local and, when the disk gets short, removes the local copies of older files you have not opened for a while. They stay in iCloud and still appear in Finder, and they download again when you open them.

macOS decides what to remove and when. It does not shrink the folder on the day you turn it on, only as space is needed. You also need an internet connection to open a file that is no longer local.

Release files yourself with Remove Download

For immediate results, do it by hand. In Finder, open iCloud Drive, right-click a file or folder and choose Remove Download. The local copy is released and the item stays in iCloud, shown with a cloud icon.

Sort the window by size to find what is worth releasing. Finished projects, archives and video are good candidates. Make sure an item has finished uploading first. A file that is still uploading shows a progress indicator, and Remove Download is not offered until it is done.

The opposite also exists. Recent versions of macOS offer Keep Downloaded in the same menu, which stops a file or folder from ever being removed locally. Use it for things you need offline.

Deleting is not the same as removing a download

If you move a file from iCloud Drive to the Trash, it is deleted from iCloud and from every device signed in to your account. That is the right action only when you no longer want the file at all.

Deleted iCloud Drive files can be recovered for a limited time. Look in the Recently Deleted folder in iCloud Drive on icloud.com or in the Files app on an iPhone. After that period they are gone.

To keep a file but take it out of iCloud, drag it from iCloud Drive to a folder that is not synced, such as a folder in your home folder or on an external drive. macOS warns you that it will be removed from iCloud. It then exists only where you put it.

Dropbox, Google Drive and OneDrive work the same way

Other sync services store their files under ~/Library/CloudStorage on current macOS, and they have the same two states. In Dropbox the option is called Make online-only. In OneDrive it is Free Up Space. Google Drive offers streaming or mirroring in its preferences, and streaming keeps files online until you open them.

The command below shows how much each service occupies locally. It only reads. If one of them is large and you no longer use the service, sign out in its app before uninstalling it, so nothing is left half synced.

du -sh ~/Library/CloudStorage/* 2>/dev/null

What not to do

Do not delete things inside ~/Library/Mobile Documents or ~/Library/CloudStorage in Finder or Terminal to save space. Those are the synced files themselves, and the deletion is sent to the cloud.

Do not turn off iCloud Drive to get space back without reading the dialog. macOS asks whether to keep a copy of your files on the Mac, which uses more space, or to remove them from the Mac.

Where Diskzy fits

Diskzy maps the whole disk, including the Library folders where sync services keep their local copies, so you can see how much each one really occupies next to everything else. Whether to release or delete a synced file is a decision to make in Finder or the service's own app, because of what deleting means there.