Why doesn’t Finder show folder sizes?

In list view it leaves the Size column blank for folders unless you turn on Calculate all sizes in View Options, and it then works them out one window at a time. Disk Usage measures the whole disk in one scan.

Can it measure folders Mail, Messages and Safari keep?

Only with Full Disk Access. Without it, macOS keeps those private, and Disk Usage says how many folders it couldn’t open and how much went unmeasured.

Does it work on external drives?

Disk Usage covers the startup disk. A folder from another drive dropped on the menu bar icon opens in its own page instead.

Will Peekaboo delete anything on its own?

No. The scan only reads. Anything you move to the Trash goes after a review and can be put back from Activity.

Peekaboo · Folder sizes

See how big every folder on your Mac is

Finder shows a folder’s size one Get Info window at a time. Peekaboo’s Disk Usage measures them all in one scan and lists them largest first, so the folder that’s grown out of hand is at the top.

Download free trial14 days free · macOS 14+ · Added in 0.1.0 · Updated November 7, 2026

What it does

Largest first, with its share: Each folder’s folders and biggest files, sorted by size or name, with the share of the folder each one takes. Click a folder to go in; Esc goes back up a level.
Down to single files: A breadcrumb runs from the disk to the folder you’re in, and a filter narrows a long folder by name. Quick Look, Show in Finder and Copy Path are a right-click away.
Drop a folder on the menu bar: Drag any folder onto the menu bar icon and it opens in Disk Usage. For Terminal, peekaboo du prints the same sizes as text or JSON.
Reading only, until you choose: The scan changes nothing. Move to Trash, for files in your home folder, comes after a review, and Undo puts them back.

How to use it

1Open Disk Usage and let it measure the disk.⇧⌘U
2Click the biggest folder, and keep going until you find what’s large.
3Trash what you don’t need, or put it back later.⌥⌘Z

When another app fits better

If one folder at a time is enough, Finder’s list view can show folder sizes too, and our guide shows how. Disk Usage measures the startup disk; for external and network drives, [DaisyDisk](/alternatives/daisydisk/) or [GrandPerspective](/alternatives/grandperspective/) (free) map those.

Questions

Why doesn’t Finder show folder sizes?: In list view it leaves the Size column blank for folders unless you turn on Calculate all sizes in View Options, and it then works them out one window at a time. Disk Usage measures the whole disk in one scan.
Can it measure folders Mail, Messages and Safari keep?: Only with Full Disk Access. Without it, macOS keeps those private, and Disk Usage says how many folders it couldn’t open and how much went unmeasured.
Does it work on external drives?: Disk Usage covers the startup disk. A folder from another drive dropped on the menu bar icon opens in its own page instead.
Will Peekaboo delete anything on its own?: No. The scan only reads. Anything you move to the Trash goes after a review and can be put back from Activity.