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, testing, and other tools that install from a disk image.

An ISO file is a disk image that virtualization software and other tools can mount and start from. 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. The conversion produces Apple's DVD and CD master format, and the .iso extension on the finished file is what lets VM software recognize it.

The ISO files described on this page are suitable for Intel-based Macs, because Apple Silicon Macs use IPSW restore images instead. macOS 27 Golden Gate and later versions require Apple Silicon, not Intel, so ISO files are only useful for older macOS versions.

Virtualization software, also called a hypervisor, lets one physical Mac run other computers inside itself. Each one is a virtual machine: a self-contained simulated computer with its own processor, memory, and storage, running its own operating system without touching the macOS on your real hardware. People use this to test software on an older or newer macOS version, run an app that no longer works on their current system, or open an untrusted file or package in an isolated environment without risking their main Mac. Snapshots make this especially useful for developers: you can revert a VM to a clean state in seconds instead of reinstalling macOS, and automated test suites can run against several macOS versions in parallel without needing a physical Mac for each one. UTM, Parallels Desktop, VMware Fusion, and VirtualBox are the common choices for virtualization software on a Mac. An ISO is the installation media you use for one of these applications: you attach it as a virtual disc, and the virtual machine starts from it and installs macOS onto its own virtual drive.

If you're on an Apple Silicon Mac, it is worth knowing about Tart as an alternative. Tart is a free, command-line virtualization tool built on Apple's own Virtualization framework, popular for scripted testing and CI pipelines. It has no ISO workflow at all: like other Apple Silicon tools, it builds macOS guests from an IPSW restore image, and it doesn't run on Intel Macs. If Tart's script-first approach fits your workflow, you can skip ISO creation entirely. If you need a point-and-click desktop experience or USB and audio integration on Apple Silicon, use UTM or Parallels Desktop instead, with an IPSW restore image as the macOS source; an ISO file only comes into play if you're setting up a VM on an Intel Mac host, using UTM, Parallels Desktop, VMware Fusion, or VirtualBox.

Some people create ISO files based on older Intel-compatible macOS versions to run with virtualization software on Linux or Windows computers but that is a violation of Apple's licensing terms, as explained below.

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Before you get started

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Know when you need an ISO file

An ISO file solves a specific problem. Apple's installer is a macOS application bundle, which other operating systems and most VM tools cannot use directly, while an ISO is a single file they can treat as installation media.

  • Virtual machines on Intel-based Macs: hypervisors such as VMware Fusion can install a macOS guest from an ISO image
  • Testing: developers start a clean macOS instance in a VM to test software without touching their own Mac
  • Convenience: a single file is easy to store and attach to a VM later, though you should keep Apple's original installer as well

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.

ISO files are for Intel-based Macs

Know your Mac's processor (Intel or Apple Silicon) before you spend time on the conversion, because the two processor families use different VM installation media.

On a Mac with Apple Silicon, VM applications do not install macOS guests from an ISO. They use an IPSW restore image, the file format Apple provides for restoring a Mac or building a macOS virtual machine. UTM and Parallels download a compatible IPSW automatically, or accept one you provide, and VMware Fusion does not run macOS guests on Apple Silicon at all. To run a macOS VM on a Mac with Apple Silicon, follow your VM application's own setup steps and skip the conversion on this page.

The ISO files described on this page are suitable for Intel-based Macs, and tools that emulate them.

Legal and practical limits for ISO use

Apple's supported workflow requires a Mac, because there is no supported way to build macOS installation media without one.

Apple's software license permits macOS virtual machines only on Apple hardware, so obtaining an ISO file does not permit you to use a Windows or Linux PC as a licensed macOS host. People do run macOS on Windows or Linux PCs in violation of that license, and the practice is well documented rather than rare. Tools such as the VMware "Unlocker" patch exist specifically to remove VMware's built-in block on showing "macOS" as a guest option on non-Apple hosts, and multiple public guides walk through using it with a macOS ISO or disk image to boot macOS inside VMware or VirtualBox on ordinary PC hardware (Vinchin, DrDonk/unlocker). Legally, this is treated as a breach of Apple's software license agreement rather than a criminal matter, and while Apple is not known to have pursued individual hobbyists over it, the practice remains unambiguously outside Apple's licensing terms. As a practical matter, macOS 27 Golden Gate and later versions require Apple Silicon, not Intel, so people who violate Apple's license are stuck with older macOS versions.

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. Double-click the package and follow its instructions, and it places the installer app in your Applications folder.

You can also download the installer with a terminal command. This command lists the full installers Apple currently offers for your Mac:

$ softwareupdate --list-full-installers

This command downloads one of them, replacing <version> with a version number from the list:

$ softwareupdate --fetch-full-installer --full-installer-version <version>

Check your free space before you begin. Three large files exist at once during the conversion: the downloaded installer, the 20 GB working image, and the converted copy of that image. Leave at least 60 GB free as a comfortable margin.

The Mac Compatibility page lists which Mac models run each macOS version, which matters when you plan to install the result on a physical Mac. A virtual machine has its own compatibility rules, because the VM application decides which guest versions it supports, so check its documentation as well.

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 with Apple's createinstallmedia tool, and converts the result to a format VM software accepts.

Open a terminal application and run these commands one at a time. They name the current macOS version, so replace the installer name in the third command, and the volume name in the fourth, to match the installer 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.

  1. The first command creates a blank 20 GB disk image, sized for the current installer. Keep the -fs HFS+J part exactly as shown, because the installer tool rejects APFS and case-sensitive volumes.
  2. The second command mounts the image at /Volumes/install_build so the next command can write to it.
  3. The third command runs Apple's createinstallmedia tool, which erases the mounted image volume (not your startup disk) and fills it with Apple's bootable installer media. Type your administrator password when asked (nothing appears as you type), then type Y and press Return to approve the erase, and click OK if macOS asks to let the terminal application access files on a removable volume.
  4. The fourth command unmounts the finished volume. The tool renames the volume to match the installer while it works, so the detach path uses the new name, "Install macOS" plus the version.
  5. The fifth command converts the writable image to Apple's read-only DVD and CD master format, which produces a .cdr file.
  6. The last command moves the file to your desktop and changes the extension to .iso. The contents do not change, but VM software that filters for ISO files can now select it.

The finished macos.iso file appears on your desktop. Before you use it, check your VM application's documentation for macOS guests. Hypervisors differ on which guest versions, host processors, and settings they support, so a macOS guest is not set up exactly like a Linux or Windows guest.

Some older installers need a different command. Apple publishes the exact createinstallmedia command for each version it offers in Create a bootable installer for macOS. The OS X El Capitan installer takes an extra --applicationpath argument, and a Mac running macOS Sierra 10.12.6 or earlier adds that argument for any installer. To convert an installer for a version older than macOS High Sierra, use an older Mac that can run that version.

Note: Apple has marked hdiutil as deprecated in favor of a newer diskutil image command. The commands above still work on macOS 26 Tahoe but may fail on later versions.

Fix common macOS ISO creation problems

The tools report problems as text messages in the terminal application. Here are the most common failures and the fix for each.

Fix "Resource busy"

The disk image is already mounted, often because a previous attempt left it attached. Close any Finder windows showing the volume, eject the volume in the Finder sidebar or with hdiutil detach, and run the failed command again.

Fix "not large enough for install media"

The working image is too small for the installer, which happens as installers grow from version to version. Detach the image, delete it with rm /tmp/macos.dmg, and recreate it with a larger size, such as -size 25g. Then repeat the commands from the second one on.

Fix "command not found"

The command cannot find the tool inside the installer app. Confirm the full installer app is in your Applications folder and that the name in your command matches it exactly, including the version name. If you only downloaded InstallAssistant.pkg, open the package first, because the package puts the installer app in place.

Fix an invalid or damaged installer app

If the tool says the installer app is not valid, or stops with a one-word "killed" message, the download is usually damaged. Delete the installer app from your Applications folder and download a fresh copy.

Fix "Operation not permitted"

macOS is blocking the terminal application from reading protected locations. Open System Settings > Privacy & Security > Full Disk Access, turn on your terminal application, and run the command again.

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.