Inside Diskscape: A Map of What Fills the Disk

Diskscape is a small Mac utility from 1dot1 that answers one question: what is filling the disk. It scans a folder or a whole drive and draws the result as rings of slices, one ring for each folder level, so the largest space users are visible before a single name has been read. This teardown walks through it screen by screen and explains the decisions behind each part.

The usual way to find out where space went is to open Finder, sort by size, and click down through folders one at a time, hoping the answer is not three levels deep inside something called Library. A picture of the whole folder at once removes that guesswork. Diskscape adds only what is needed to act on what the picture shows, and it is careful never to change a file unless asked.

Every disk from the menu bar

Diskscape lives in the menu bar behind a ring-shaped icon. Clicking it opens a panel that lists every mounted disk: the startup disk, a backup drive, a camera card. Each one has a bar for used space, the free space on the right, and a line underneath with how much is used of the total.

Beside each disk is a Scan button that measures the whole of it, and at the bottom are Scan Home and Open Diskscape. The panel is there for the quick look, the moment a warning about low storage appears, and it hands over to the window only when there is real scanning to do. A right-click on the icon gives the same choices as a menu, along with the settings.

One setting is worth pointing out. Show Free Space in Menu Bar puts the startup disk’s free space next to the icon and refreshes it every minute, which turns the app into a quiet gauge that is always visible without being opened.

A scan that reads many folders at once

In the window, Home scans the Home folder and Choose picks any folder or disk. The scan reads many folders at the same time rather than walking the tree one branch after another, and the window shows the number of files and the space found so far, with the path currently being read underneath. In testing, a 70 GB folder took about 25 seconds. The real figure depends more on how many files there are than on how large they are.

Two measuring decisions keep the numbers honest. Sizes are the space each file actually takes on the disk, which can differ a little from the size Finder shows for small files, because that is the space that comes back when a file goes. And symbolic links are not followed, so a shortcut can never make the same folder count twice.

Cancel stops a scan at any time, and Rescan measures again after tidying up. The first scan of the Home folder makes macOS ask whether Diskscape may read Desktop, Documents and Downloads. Diskscape only reads names and sizes; it does not open file contents.

Rings instead of a tree

The chart is a sunburst. The circle in the middle is the folder being viewed, with its total size and file count. The first ring holds the folders and files directly inside it, and each slice takes a share of the circle equal to its share of the space. Every ring further out is one level deeper.

The reason for rings rather than a list is that size and depth are visible together. A large slice in the first ring is a big folder; a large slice far out on the edge is a single heavy item buried deep, the kind of thing a sorted list only reveals after several clicks. Hovering over a slice shows its name, size and percentage in a small label, and the matching row is highlighted in the list beside the chart, so the picture and the names never drift apart.

Click to go deeper

Clicking a folder’s slice zooms into it. The rings redraw around that folder, the centre shows its own total, and the list beside the chart follows. The path at the top grows a step, Home then Movies, for example.

Going back is deliberately easy, because exploring only feels safe when the way out is obvious. Click the middle circle, the back arrow, or any name in the path to jump straight to that level. There is no separate navigation mode to learn; the chart itself is the navigation.

The list beside the chart

Contents lists what is inside the current folder, largest first, with the size, the percentage and a bar for each row. Clicking a row selects it and double-clicking a folder zooms into it, exactly as clicking its slice would.

Three buttons sit under the list. Reveal shows the selected item in Finder. Quick Look previews it without opening another app, and pressing Space does the same, as it does in Finder. Move to Trash sends it to the Trash, and a right-click on any row offers all three.

Move to Trash is where a disk tool can do harm, so it is built cautiously. Diskscape always asks first and says how much space the item will free. Items only ever go to the Trash, never deleted outright, so anything can be put back from the Trash in Finder. The rings and totals update straight away, without a rescan, and the space itself returns when the Trash is emptied.

The biggest files, and what kind they are

Rings are good at showing folders, but sometimes the question is simply which single items are largest. Largest Files lists the hundred biggest items in the scan, each with the folder it sits in, so a forgotten installer in Downloads or an old video export stands out immediately. Apps and other bundles, such as a Photos library or a video project, are listed whole, the way Finder shows them, because that is how they are kept or thrown away.

File Types adds the scan up by kind: Video, Images, Apps, Archives and disk images, and Everything else, each with its size, its share and the number of items. It answers a different question from the rings, whether the problem is a lot of video or a lot of everything, and it takes no extra scanning.

Private folders and Full Disk Access

macOS keeps some folders private, such as Mail, Messages and parts of Library. Rather than stopping or quietly under-reporting, Diskscape counts folders it is not allowed to read as empty, shows them with a lock, and puts a note under the chart saying how many there were.

For complete results, Open Full Disk Access opens the right page of System Settings, where Diskscape can be switched on. The app never changes that setting itself, and it is entirely optional: without it, everything else still works. This is also one of the honest limits of any disk scan. macOS reserves space for snapshots and system files that no scan can see, so a scan total can be smaller than the used space the menu bar panel reports.

Built in black and white

Like the other 1dot1 Mac apps, Diskscape is greyscale. The chart uses shades of grey rather than a rainbow of colours, with darker slices nearer the middle and lighter ones towards the edge, so the eye reads size and depth instead of trying to decode what a colour means. The hovered or selected slice goes darker still, which is enough to find it.

The icon is a ring broken into segments, the same shape as the chart, and the menu bar glyph repeats it at a smaller size. Diskscape is a universal app for Apple silicon and Intel Macs and runs on macOS 13 Ventura or later.

How to use it, feature by feature

The same instructions are in the guide inside the download.

Installing it

1. Unzip the download and drag Diskscape.app into the Applications folder, then open it. A ring-shaped icon appears in the menu bar.
2. Diskscape is signed and notarized by Apple, so it opens with a normal double-click.

Checking the disks from the menu bar

1. Click the menu bar icon to see every mounted disk with a bar for used space, the free space, and how much is used of the total.
2. Click Scan beside a disk to scan the whole of it, or Scan Home to scan the Home folder.
3. Click Open Diskscape to bring up the scan window.
4. Right-click the icon for a menu with the same choices, plus the settings.

Scanning

1. In the window, click Home to scan the Home folder, or Choose to pick any folder or disk.
2. Watch the file count and space found so far; click Cancel to stop at any time.
3. Allow access to Desktop, Documents and Downloads when macOS asks during the first Home scan, so those folders can be measured.
4. Click Rescan after tidying up to measure again.

Reading the rings

1. The circle in the middle is the folder being viewed, with its total size and file count.
2. The first ring holds what is directly inside it; each ring further out is one level deeper.
3. Hover over a slice to see its name, size and percentage.
4. Click a folder’s slice to zoom into it.
5. Click the middle circle, the back arrow, or any name in the path at the top to go back up.

The list beside the chart

1. Contents lists the current folder, largest first, with size, percentage and a bar.
2. Click a row to select it, and double-click a folder to zoom into it.
3. Click Reveal to show the selected item in Finder.
4. Click Quick Look, or press Space, to preview it.
5. Right-click any row for the same actions.

Largest files and file types

1. Click Largest Files for the hundred biggest items in the scan, with the folder each one is in.
2. Click File Types to see the scan added up as Video, Images, Apps, Archives and disk images, and Everything else.

Moving things to the Trash

1. Select an item and click Move to Trash, right-click it, or press Command-Delete.
2. Read the confirmation, which says how much space will be freed, and confirm.
3. The rings and totals update straight away. Put anything back from the Trash in Finder if needed.
4. Empty the Trash in Finder to get the space back.

Full Disk Access

1. Look for the note under the chart saying how many folders could not be read; those folders show a lock.
2. Click Open Full Disk Access and switch Diskscape on in System Settings.
3. Click Rescan for complete results. Without it, everything else still works.

Settings

1. Turn on Show Free Space in Menu Bar to see the startup disk’s free space beside the icon, refreshed every minute.
2. Turn on Open at Login to keep Diskscape in the menu bar from the moment the Mac starts.
3. Both are in the panel’s ellipsis menu and in the right-click menu.

If something does not happen

1. A folder shows a lock and counts as empty: macOS did not allow it to be read. Turn on Full Disk Access, then click Rescan.
2. The total is smaller than the disk’s used space: the scan covered one folder, or some folders were private. Scan the whole disk with Full Disk Access on; snapshots and system files remain invisible to any scan.
3. Move to Trash says the item could not be moved: it may be in use, locked or owned by the system. Quit the app using it, or leave it alone.
4. Space does not come back after moving things to the Trash: empty the Trash in Finder.
5. Quick Look shows nothing: some file types have no preview on macOS. Reveal in Finder still works.

Finding what is inside System Data

The storage bar in System Settings often shows a large grey block called System Data, and it is one of the most searched questions about Mac storage. It is a catch-all for everything macOS does not file under apps, documents or photos: caches, logs, app support files, virtual memory and Time Machine local snapshots.

A scan of the Home folder in Diskscape makes much of it visible. Library holds Caches, Logs and Application Support, and the rings show at once which of them have grown, often because of apps that were removed long ago. Local snapshots and protected system files are handled by macOS and do not appear in a scan, and macOS clears local snapshots by itself when space runs low.

Get Diskscape

Diskscape is available on 1dot1 as a single download, with the guide, a README and the licence inside the zip.

Get It Now