Reinstall of older macOS on MacBook Air M1 throws error com.Apple.OSInstallerSetup.error 702

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Reinstall of older macOS on MacBook Air M1 throws error com.Apple.OSInstallerSetup.error 702

Reinstall of older macOS on MacBook Air M1 throws error com.Apple.OSInstallerSetup.error error 702 message in the middle of the process.

I have tried to install macOS Big Sur on the external drive using the script below to copy the App Store Installer to my external SSD volume connected with Thunderbolt 3, also with USB 3.1 (tried different dongles). The script with createinstallmedia tool is described here:

Create a bootable macOS installer

It creates the bootable installer from macOS Sequioa, but in the middle of setup the installation stops with the error described in the topic title. The same happens both with Big Sur and Monterey downloaded from the App Store.

Please help to fix this error. Finally I was able to install only macOS Sequioa on my external SSD using the recovery partition, but I need all macOS versions compatible with my MacBook Air M1 for testing purposes / development. I did plan to install different firmware on different 1 TB SSD volumes like I did with my Intel Macs. Thanks!

MacBook Air 13″

Posted on Apr 24, 2025 07:20 PM

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Answer 1

AlexCramer Author

Level 1

4 points

Apr 27, 2025 01:17 AM in response to AlexCramer

That is what I found on issue:

To downgrade firmware and macOS on an Apple Silicon Mac (M1), you need to use Apple Configurator 2 on a second Mac with the correct IPSW restore file for the macOS version you want to downgrade to. This process will restore the entire system including firmware and recovery partition, erasing all data, so back up your files first.

Steps to Downgrade Firmware on M1 Mac:

Download the correct IPSW restore file for the macOS version you want (e.g., Big Sur).
Put the M1 Mac into DFU mode:

- Shut down the Mac.
- Connect it to the second Mac via USB-C.
- Use a specific key combination to enter DFU mode (varies by model).

Use Apple Configurator 2 on the second Mac to restore the M1 Mac with the downloaded IPSW file. This will reinstall macOS and downgrade the firmware.

Important Notes:

You can only downgrade to macOS versions that originally shipped with your Mac or later.
Downgrading will erase your data, so create a backup beforehand.
Traditional USB installers or macOS Recovery generally cannot downgrade firmware on M1 Macs; Apple Configurator 2 is required for firmware downgrade.
Apple limits downgrades by removing signatures from older IPSW files after a short time, so use currently signed IPSW files.

This is the official and safest method to downgrade firmware and macOS on M1 Macs.

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Reinstall of older macOS on MacBook Air M1 throws error com.Apple.OSInstallerSetup.error 702

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