What does Optimize Mac Storage actually do?

It replaces local copies of iCloud files, photos and watched Apple TV purchases with small placeholders, downloading the originals again on demand. It frees space but requires an internet connection to reopen those files.

Should I turn on Store in iCloud?

Only if your iCloud plan has room for your library. Otherwise syncing stops and nothing is offloaded. Check the size of your Desktop, Documents and Photos before enabling it.

How often should I clean my Mac?

A ten-minute review once a month is enough for most people: empty the Trash and Downloads, delete duplicates, and clear caches for apps you no longer use.

How to Optimize Mac Storage

What “optimize storage” means on macOS

Apple groups several unrelated features under one label. In System Settings > General > Storage you will find recommendations such as Store in iCloud, Optimize Storage, Empty Trash automatically and Reduce Clutter. They do very different things, and only some are worth turning on.

The four built-in options, reviewed

Store in iCloud

Moves Desktop, Documents and full-resolution photos to iCloud, leaving placeholders locally. Effective — but only if your iCloud plan is big enough. If the plan fills up, syncing stops and you free nothing. Check the size of those folders first.

Optimize Storage

Removes Apple TV movies and shows you already watched and keeps only recent Mail attachments. Safe, but the amount recovered is small unless you buy a lot of video.

Empty Trash automatically

Deletes items that have been in the Trash for 30 days. Worth enabling — the Trash is the most common place where forgotten gigabytes sit.

Reduce Clutter

Just a browser for large files, downloads and unsupported apps. Useful for a quick look, but it does not see caches, duplicates, old backups or developer artifacts — which is where most of the space usually hides.

What the built-in tools miss

System Data — caches, logs and snapshots grouped into one opaque gray bar. See our System Data guide.
Duplicates — identical files in different folders are never flagged.
Old device backups — iPhone and iPad backups stored in your home folder.
Developer artifacts — Xcode derived data, simulators, Docker images, node_modules.
Leftovers from uninstalled apps — support files that stay after the app is gone.

A monthly routine that works

Open Storage and note the free space, so you can compare next month.
Empty the Trash and Recently Deleted in Photos, Notes and Mail.
Sort ~/Downloads by size and clear installers and archives.
Scan for duplicates and keep one copy of each.
Clear caches for apps you stopped using.
Delete device backups and Time Machine local snapshots older than a month.
Archive finished projects to an external drive.

Ten minutes a month keeps a Mac from ever hitting the “disk almost full” warning. If you are already there, start with the full cleanup guide instead.

How much free space should you keep?

Keep at least 10–15% of the disk free. macOS needs headroom for swap memory, updates and snapshots; below that threshold apps slow down and updates start to fail.

Turn the routine into one scan

DeleteIt checks every category above in a single pass — large files, duplicates, caches, backups and leftovers — and shows how much each one returns before you delete anything.

Scan my Mac for free

Frequently asked questions

Does optimizing storage delete my files?

Apple's options do not delete originals — they move them to iCloud and download them again on demand. You do need an internet connection to reopen offloaded files.

Does a fuller disk make a Mac slower?

Yes, once free space drops below roughly 10%. macOS relies on free disk for virtual memory and temporary files.

Is it safe to clear caches regularly?

Yes. Apps rebuild caches automatically; the first launch afterwards is just slightly slower.