everyday mac tools

Other Volumes in Disk Utility: what is using that space on a Mac

· 6 min read

When you select Macintosh HD in Disk Utility, the bar across the top splits into Used, Other Volumes and Free. Other Volumes is the space taken by the other APFS volumes that share the same disk: the ones macOS creates for itself to start up, recover, swap memory and stage updates, plus any volume that you or an app added later. A few gigabytes is normal. A figure in the tens of gigabytes usually means a pending macOS update, heavy swap, or an extra volume nobody remembers making, and Terminal will tell you which in under a minute.

Why one disk holds several volumes

Modern Macs format the internal drive as APFS. An APFS disk holds a container, and the container holds volumes that all draw on one shared pool of free space. No volume has a fixed size, so any of them can grow into the free space, and that is how a volume you never open can take room from your files.

Since macOS Catalina, the startup disk has been split in two. Macintosh HD is the system volume, sealed and read-only, holding macOS itself. Macintosh HD - Data is where your apps, your home folder and everything you create live. Disk Utility treats the pair as one, and that is what the Used figure covers.

Alongside them sit support volumes that Disk Utility keeps out of the sidebar even when you choose View, Show All Devices. Because it does not show them individually, it adds them up and calls the total Other Volumes.

See each volume with diskutil

Terminal shows every volume and exactly how much each one consumes.

  1. Open Terminal, in Applications, Utilities.
  2. Run:
diskutil apfs list
  1. Find the container that includes Macintosh HD. You may see more than one container; ignore the others for now.
  2. Each volume in it has a line for its role, shown in parentheses as (System), (Data), (Preboot), (Recovery), (VM) or (Update), a Name line, and a Capacity Consumed line.

To cut the output down to what matters:

diskutil apfs list | grep -E "Name:|Role|Consumed"

Add up everything except the System and Data volumes and you have the Other Volumes figure. The largest entry is usually the answer.

What each volume does, and when it gets big

Preboot. Files the Mac needs before macOS itself loads, including what it uses to unlock a FileVault disk at the login screen. It is a few gigabytes on most Macs and changes with macOS updates. Leave it alone.

Recovery. The environment you get when you start the Mac in Recovery mode, used to reinstall macOS or repair the disk. It is modest in size and essential. Leave it alone.

VM. Swap files, which macOS writes when apps need more memory than the Mac has, and on Intel laptops a sleep image as well. This is the volume most likely to be large on a busy Mac. Restarting clears the swap, so if VM is large, restart and run the command again. If it climbs straight back, the Mac is under memory pressure, and Activity Monitor’s Memory tab shows which apps are responsible. Swap files on a Mac goes into what to do about it.

Update. A macOS update that has been downloaded and prepared but not yet installed. It can be large while it waits. Open System Settings, General, Software Update: if an update is ready, installing it is the dependable way to clear this volume. Do not try to delete it by hand.

Anything with a name you recognize. A volume called something like macOS Beta or Test was added by a person, usually to try a second copy of macOS without touching the main one. Now and then an app adds a volume for its own use, and its name normally points to the app. These are the only entries on the list that are safe to remove, and only once you are sure nothing on them is needed.

One thing you will not find on the list is Time Machine’s local snapshots. They are charged to the data volume rather than listed as a volume of their own, so they show up as used space, not Other Volumes. Time Machine local snapshots are taking space covers how to see and thin them.

Removing an extra volume you no longer need

This deletes everything on the volume, so copy off anything you want first and check that your Time Machine backup is recent.

  1. Start up from your normal Macintosh HD. You cannot delete the volume the Mac is running from.
  2. Open Disk Utility and choose View, Show All Devices.
  3. Select the extra volume in the sidebar. Read its name twice.
  4. Click the minus button in the toolbar, or choose Edit, Delete APFS Volume.
  5. If the volume holds a copy of macOS, Disk Utility offers to delete the whole volume group, meaning its system and data halves together. That is the right choice for a second macOS install you are finished with.

The space returns to the shared pool immediately, with no restart needed. Run diskutil apfs list again to confirm.

There is a Terminal equivalent, diskutil apfs deleteVolume followed by the volume’s identifier, but Disk Utility shows you the name of what you are about to delete, which is the safer habit.

Never delete Preboot, Recovery, VM, Update or the Data volume. The Mac depends on all of them, and removing one can leave it unable to start up.

When the space is in volumes you cannot touch

If the list shows nothing extra and Other Volumes is still large, the cause is almost always VM or Update, and both shrink on their own once you restart or install the waiting update. If the real pressure is elsewhere and Storage in System Settings shows a large System Data figure, The Mac says storage is full, but the folders do not add up walks through the other usual hiding places.

For the space inside the data volume, Crumb runs a read-only audit of the whole Mac that breaks System Data into its parts (caches, logs, swap, temporary files and leftovers) and shows Time Machine local snapshots on the internal drive, so you can see what is growing before you change anything. Deleting an APFS volume stays a job for Disk Utility. The audit and one full cleanup are free; the rest of Crumb is a $9 one-time unlock for up to two Macs.

Questions

Is it safe to delete Other Volumes? Not the system ones. Preboot, Recovery, VM and Update are part of how macOS works. Only a volume you or an app added on purpose is safe to remove, after a backup.

Is Other Volumes the same as System Data? No. System Data is a category in System Settings, Storage, and it describes files. Other Volumes is Disk Utility’s view, and it describes volumes. The two are measured differently, so the numbers rarely match.

Will erasing the Mac and reinstalling shrink it? Only if the space was in an extra volume or a stuck update. The support volumes are recreated on a fresh install and soon settle back to their usual size.