Optimize Storage on Mac: what each recommendation does

1. Where the recommendations live

Open System Settings → General → Storage. Apple’s page on optimizing storage space describes the Recommendations shown there and adds a line people miss: when space is needed, macOS also clears caches and logs that are safe to delete on its own. So the recommendations are about your files, not about System Data.

The words are reused elsewhere, which causes confusion. Photos has its own Optimize Mac Storage setting, iCloud Drive has one too, and the recommendation called Optimize Storage is a third thing. This guide takes the three recommendations in order and says which other settings each one flips.

2. Store in iCloud

Apple’s description: store files from your Desktop and Documents folders in iCloud Drive, store photos and videos in iCloud Photos, store messages and attachments in iCloud, and optimize storage by keeping only recently opened files on your Mac when space is needed. It is the biggest saving and the biggest change, because it turns on three syncs at once and lets macOS evict older files to the cloud.

Three costs follow. Everything now counts against your iCloud storage plan. A file that was evicted needs a connection to open, which matters on a laptop used offline; Apple documents the Download Now and Remove Download controls in iCloud Drive for managing that by hand. And deleting a synced file deletes it everywhere. Apple notes you can adjust the pieces later in the iCloud pane of Apple Account settings, in Photos settings and in Messages settings.

3. Optimize Storage

Apple’s description: save space by automatically removing Apple TV movies and TV shows you have already watched, and by keeping only recent email attachments on this Mac when storage space is needed. Both are cheap and reversible. A watched purchase downloads again from the TV app, and older attachments stay on the mail server; Mail fetches one when you open it.

The attachment half is the same control as Mail’s Download Attachments setting, which the Mail guide covers. If Mail is a large part of your storage, that setting does the work whether or not you use the recommendation.

4. Empty Trash Automatically

Apple’s description: automatically erase items that have been in the Trash for more than 30 days. It is the same option as Finder → Settings → Advanced → Remove items from the Trash after 30 days, and Apple says you can change it there later. Apple also notes that items deleted from iCloud Drive are emptied after 30 days regardless of the setting.

The cost is the safety net. Put Back works only while an item is still in the Trash, so with this on, anything you deleted more than a month ago is gone. Turn it on if you never look in the Trash anyway; leave it off if you use the Trash as a holding area.

5. Turning each one off, and what none of them do

Each recommendation is undone in the app it changed rather than in Storage settings.

• Desktop and Documents in iCloud, and on-demand files: the iCloud pane of Apple Account settings, under iCloud Drive. Download anything you need offline first.
• Photos: Photos → Settings → iCloud, choose Download Originals to this Mac. Apple’s Photos guide covers the two options.
• Messages: Messages → Settings → iCloud, where Messages in iCloud can be turned off.
• Email attachments: Mail → Settings → Accounts → Account Information, set Download Attachments to All.
• Trash: Finder → Settings → Advanced, clear Remove items from the Trash after 30 days.
• None of these touch developer caches, app containers or the rest of System Data. For that part, the System Data and Library guides apply, and a free local scan such as ClearDisk’s shows those folders with allocated sizes and moves what you choose to the Trash first.