Storage Studio and Optimise Mac Storage

iCloud's Optimise Mac Storage and Storage Studio's cloud tools both free space by keeping files in the cloud instead of on your Mac. The difference is who decides, and when.

What Optimise Mac Storage does

It's a switch in iCloud Drive's settings in System Settings. When it's on, macOS keeps your iCloud Drive files on the Mac while there's room. When space runs short, it makes older files online-only on its own; they download again when you open them. macOS chooses which files and when — you don't need to do anything.

What Storage Studio adds

• Space now, for a folder you choose. Optimize Cloud Storage… in the More menu lists the cloud folders it finds on your Mac — your iCloud Drive and the folders of other cloud apps you use. Pick one and it makes every downloaded file in it online-only in one pass, then reports how much space came back. Files that are open, or already online-only, are left alone. (In the Advanced View the same command is called Optimise Cloud Storage Locally.)
• A timer for files you open. For files in the Storage Studio location in Finder, Keep opened files on this Mac sets how long an opened file stays downloaded — 24 hours unless you change it — before it goes back to online-only by itself. Files that are open or still uploading are never removed.

%% caption: Who decides when a cloud file goes back online-only
flowchart TD
  A[A downloaded cloud file] --> B{Which tool?}
  B -->|Optimise Mac Storage| C[macOS waits until space runs short]
  C --> D[macOS picks older files]
  B -->|Optimize Cloud Storage| E[You pick a folder and run it now]
  B -->|Keep opened files on this Mac| F[The time you chose passes]
  D --> G[File becomes online-only]
  E --> G
  F --> G

Using both

Leaving Optimise Mac Storage on is a sensible default for iCloud Drive. Reach for Storage Studio when you want the space straight away — before a big download or a macOS update — or for cloud folders that macOS's switch doesn't cover. Either way the files stay safe in your account.

See also: Optimise Cloud Storage Locally · Keep opened files on this Mac · Keep opened files versus iCloud's Remove Download