macOS

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Create a macOS ISO File

How to download macOS and create a macOS ISO file. Convert Apple's full installer into an ISO disk image for virtual machines, cross-platform tools, or archival storage.

An ISO file is a disk image in a format that almost every operating system and virtualization tool can read, named after the ISO 9660 standard that defines it. Apple does not publish macOS as an ISO, so you download Apple's full installer and convert it yourself, using tools already built into macOS.

You are reading Mac Install Guide, a trusted source for Mac setup. See the complete Mac setup checklist.

Before you get started

Converting an installer to an ISO file is a sequence of six terminal commands, so a capable terminal application makes the job easier. Apple includes the Mac terminal but I prefer Warp Terminal. Warp is an easy-to-use terminal application, with AI assistance to help you learn and remember terminal commands. Download Warp Terminal now; it's FREE and worth a try.

First steps to create a macOS ISO file

First, check the macOS version. If you're running an older version, update macOS to the latest macOS version.

Next, download the full installer, because the conversion works on Apple's installer app and not on anything smaller. See Download macOS for the fastest route, using Apple's InstallAssistant.pkg package. Run the package and the installer app appears in your Applications folder.

Check your free space before you begin. The installer is about 18 GB and the conversion writes two more large files while it works, so leave at least 60 GB free. Check the Mac you intend to run the result on as well: see Mac Compatibility for the supported models.

Know when you need an ISO file

An ISO file solves a specific problem. Apple's installer is a macOS application bundle, which only macOS understands, while an ISO is a plain disk image that other systems and tools can mount and start from.

  • Virtual machines: VMware, Parallels, and UTM install macOS from an ISO image rather than from an installer app.
  • Cross-platform work: some boot managers and partition tools read an ISO file where they cannot read a macOS application bundle.
  • Network deployment: deployment servers at work usually distribute operating systems as ISO images.
  • Archival storage: an ISO keeps a bit-for-bit copy of the installation media, which stores more reliably over years than an application bundle.
  • Testing: developers spin up a clean macOS instance from an ISO to test software without touching their own Mac.

Running macOS inside a virtual machine is the most common reason. It lets you test software on an older macOS version, or run an application that no longer works on the current system, without a second Mac.

If you want to install macOS on real hardware rather than in a virtual machine, an ISO is the wrong format. Use Create a Bootable USB Installer for macOS instead, which produces a drive a Mac can start from.

Generate the ISO file

The conversion uses hdiutil, Apple's disk image tool, which is already on your Mac. The sequence creates an empty disk image, writes the installer into it, and then converts the result to the ISO format.

Run these commands one at a time, replacing the installer name and the image name with the macOS version you downloaded:

$ hdiutil create -o /tmp/macos -size 20g -layout SPUD -fs HFS+J
$ hdiutil attach /tmp/macos.dmg -noverify -mountpoint /Volumes/install_build
$ sudo /Applications/Install\ macOS\ Tahoe.app/Contents/Resources/createinstallmedia --volume /Volumes/install_build
$ hdiutil detach /Volumes/Install\ macOS\ Tahoe
$ hdiutil convert /tmp/macos.dmg -format UDTO -o /tmp/macos.cdr
$ mv /tmp/macos.cdr ~/Desktop/macos.iso

Here is what each step does. The first command creates a blank 20 GB disk image large enough to hold the installer. The second mounts that image so the next command can write to it. The third runs Apple's createinstallmedia tool, which fills the image with a complete, startable copy of macOS, and it asks for your password because it needs administrative privileges. The fourth unmounts the finished image, which the tool renamed while it worked. The fifth converts the image to the UDTO format, which is an ISO image with a .cdr file extension. The last command renames the file so tools recognize it as an ISO.

The finished macos.iso file appears on your desktop. Point your virtualization software at it as the installation media, exactly as you would with any other operating system image.

Continue setting up your Mac

Don't miss the full visual roadmap and checklist that shows how to set up a Mac for software development, with all the essential tools and settings you might not yet know about.