• Virtualisation
  • Developer

UTM virtual machines grow as you use them, and shrinking them takes one extra step

Each UTM VM is a bundle holding its virtual disks, which grow and rarely shrink by themselves. Where they live, how to measure them, and how to reclaim space.

4 min read

UTM stores each virtual machine as a .utm bundle containing its disk images. A Linux or Windows VM grows as you install and download things, and deleting files inside the VM does not automatically make the file on your Mac smaller.

du -sh ~/Library/Containers/com.utmapp.UTM/Data/Documents/*.utm 2>/dev/null
mdfind -name .utm | head

Reclaim space from a VM

  1. Inside the VM, delete what you do not need and empty its own trash.
  2. Shut the VM down.
  3. In UTM, edit the VM, select its drive, and look for the option to reclaim or compress space, available in recent versions for QCOW2 disks.
  4. Measure the .utm bundle again.

Remove old VMs

Delete VMs you no longer use from UTM's list, which removes the bundle. VMs imported or kept elsewhere may be outside the default folder; the mdfind command above finds them.

Keep large VMs off the Mac

UTM can open a VM from an external SSD. Move the bundle there with UTM quit, then open it from the drive.

Other virtualisation: virtual machines taking up space, Vagrant boxes.

Common questions

Where does UTM store virtual machines on a Mac?

In ~/Library/Containers/com.utmapp.UTM/Data/Documents, as .utm bundles, unless you saved them elsewhere.

Why doesn't my UTM VM get smaller after deleting files inside it?

The virtual disk keeps its size until space is reclaimed. Shut the VM down and use the reclaim or compress option on its drive.

Can I run a UTM VM from an external drive?

Yes. Move the .utm bundle to the drive with UTM quit, then open it from there.

Read next