Storage Inspector

Storage Inspector shows what is actually using space on your Mac. Every number on it is measured on your Mac rather than estimated. It also shows what grew since the last measurement and how much your automatic backups are holding, and you can move a big folder to your external drive from here and move it back later.

Open it from the More menu (•••) → What's Using Space…, or from the What's Using Space card on the Home screen. In the Advanced view it's the Storage Inspector button in the popover.

What's on the screen

The sections run from top to bottom in the order you're most likely to need them.

• What changed: three figures. Gone is space taken by files that weren't there at the last measurement. Pinned is space your Mac is holding in automatic backups. Reclaimed is space released since the last measurement without you doing anything. Below them, the folders that grew or shrank the most.
• Biggest on this disk: your home folder, measured, biggest first. Click the arrow next to a folder to look inside it, or the folder icon to show it in Finder. A shortcut is shown as shortcut and counted where its contents really live.
• Space held by backups: how much your Mac's local snapshots are holding, with the age of each one. The Local Snapshots button opens the screen where you can review and remove them. See Local snapshots.
• Known quick wins: caches Storage Studio knows about, with their sizes, and the place to move a big one to your drive. This section starts collapsed, and caches that are already empty are counted rather than listed.

Click Measure again at the top to walk the disk again. Results appear as they arrive.

Moving a folder to your external drive

In Known quick wins, a row that can be moved shows a Move to NVMe button (NVMe is the app's name for your fast external drive). A row gets one when it's at least 100 MB and safe to move. Some rows can't be moved, and the row says why:

• Protected: an app's own files, including its settings and sign-ins. Storage Studio only moves the part an app rebuilds by itself.
• The Trash: its size is shown, but there's no button. Emptying the Trash is the one thing Storage Studio can't undo, so it isn't offered here. See The Trash and the space it holds.

%% caption: What happens when you click Move to NVMe on a row
flowchart TD
  A[Click Move to NVMe] --> B[Confirm sheet]
  B --> C{Is an app using files in the folder?}
  C -->|Yes| D[Apps listed, with Quit and Quit all]
  C -->|No| E[Copy to the drive]
  D --> E
  E --> F{Did the copy check out?}
  F -->|Yes| G[A shortcut replaces the original]
  F -->|No| H[Nothing changes - your folder stays as it was]
  G --> I[Folder appears in the Relocated panel]

When an app is using the folder, the sheet lists it and offers Quit for each app or Quit all. You can also continue anyway, but that may interrupt the app. The sheet also offers Keep auto-syncing new files to NVMe: with it on, new files that apps write into the folder later are moved to the drive in the background too. See Rules: moving folders automatically.

When it finishes you'll see ✓ Checked — the original place now points at the copy on your drive, so your apps keep working. If it doesn't finish, Move did not complete — your source folder was not modified.

If a copy of the folder is already on your drive, the sheet says so and asks what to do with it:

• Keep both (the default) — the copy on the drive is renamed with today's date, for example Downloads (drive copy 27 Oct 2026), and kept exactly as it is. Your folder moves in beside it.
• Merge — your folder's files join the copy on the drive. Where both have a file with the same name but different contents, both are kept: the drive's one is renamed with the date. Identical files are left alone and nothing is deleted.
• Replace — the copy on the drive is removed first and isn't kept anywhere, so you type Replace to confirm, and the button reads Move and replace.

iPhone and iPad backups

The backups Finder makes of your iPhone and iPad appear under Space held by backups. With your drive connected they have a Move to fast drive… button: Storage Studio copies them to the drive, checks that every file arrived, and only then frees the space on your Mac. Finder carries on backing up there, so keep the drive connected when you back up or restore a device. Move back… brings them home whenever you like, checked the same way. Neither runs while a device backup is in progress, and if a copy doesn't match, it's removed and nothing on your Mac changes.

The Relocated panel and Move back

The Relocated button at the top right opens a panel listing every folder that currently lives on your drive, with when it was moved. Each one has a Move back button that copies it back to your Mac and removes the shortcut. If apps are using the folder, you're shown which, as when moving it out. If you've added files since the move, the confirmation says how many.

See also: Where did my space go? · Moving a folder back · The shortcut left behind after a move · When an app is holding a folder open · Emergency Space