How can I downgrade from macOS 27 to macOS 26?

How to Downgrade a 13-inch Apple Silicon MacBook Pro from macOS 27.0 to macOS Tahoe 26

Downgrading from macOS 27.0 to macOS Tahoe 26 may be possible on a 13-inch MacBook Pro with an M1 or M2 chip. However, Apple does not provide a universal, one-click downgrade procedure for Apple Silicon Macs. The correct approach depends on whether macOS 27.0 is a beta or public release.

1. Identify your Mac and back it up

Go to Apple menu → About This Mac and check whether your Mac has an M1 or M2 chip.

Both the 13-inch M1 (2020) and M2 (2022) MacBook Pro support macOS Tahoe 26.

Apple: macOS Tahoe compatibility

Apple: Back up your Mac with Time Machine

Important: A clean installation can erase your internal drive. Back up your Mac, separately copy essential files, and verify that your backups are accessible before proceeding.

2. If macOS 27.0 is a beta

First, turn off future beta updates under System Settings → General → Software Update → Beta Updates → Off, if available. This does not remove the installed beta.

Consult Apple's official beta software restoration instructions. For Apple Silicon Macs, restoring previously released software may require Apple Configurator and another compatible Mac. The process can erase your data.

Alternatively, if you have a compatible macOS Tahoe 26 installer, follow the bootable-installer procedure below.

3. If macOS 27.0 is a public release

A clean installation using a compatible macOS Tahoe 26 bootable installer may be an option.

Step A: Download macOS Tahoe 26

Use Apple's official macOS download instructions.

Step B: Create a bootable USB installer

You need a USB drive with at least 32 GB of storage. The process erases the USB drive.

Follow Apple's bootable-installer instructions.

If the installer is in Applications and your USB drive is named MyVolume, open Terminal and run:

sudo /Applications/Install\ macOS\ Tahoe.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

Replace MyVolume if your USB drive has a different name.

Step C: Start from the USB installer

1. Shut down your Mac.
2. Connect the USB installer.
3. Press and hold the power button until startup options appear.
4. Select the installer if offered and click Continue.

If the installer is rejected or does not appear, stop and investigate compatibility before erasing the internal drive.

Step D: Erase the internal startup disk

Warning: This permanently deletes data on the erased disk.

1. Open Disk Utility.
2. Select the internal Macintosh HD volume, not the USB installer.
3. Click Erase.
4. Name the volume Macintosh HD and choose APFS if prompted.
5. If Erase Volume Group appears, select it.
6. Confirm the operation and wait for it to finish.
7. Quit Disk Utility.

Do not erase unrelated volumes or the physical disk indiscriminately. If the expected options are missing, stop and consult Apple's instructions.

Official guide: Erase a Mac with Apple silicon.

Step E: Install macOS Tahoe 26

Return to the installer, select Install macOS Tahoe, and follow the instructions. Select the erased Macintosh HD as the destination.

If installation fails because of compatibility, firmware, or security restrictions, stop rather than repeatedly erasing the Mac.

After installation, complete setup and migrate your personal files. A backup created under macOS 27 may not restore the entire system to macOS 26.

4. Important limitations

Recovery is not a guaranteed downgrade method. It normally reinstalls the current version of the most recently installed macOS, although the version offered can vary.

DFU restore is not a guaranteed downgrade method. It may be necessary in some recovery situations but can erase the Mac.

Older installers may be restricted by compatibility or firmware requirements.

Downgrading can cause data loss and may leave you without newer security fixes.

Apple references:

Reinstall macOS

Revive or restore Mac firmware

Conclusion

A downgrade from macOS 27.0 to macOS Tahoe 26 may be achievable, but it is not guaranteed. For a beta, begin with Apple's beta-restoration guidance; for a public release, investigate a compatible bootable installer and clean installation.

Before erasing your Mac, confirm whether macOS 27.0 is a beta or public release, verify your backup, and ensure that your intended installation method is compatible with your exact Mac model.

Reverting to an older major version of macOS is not simple. You need to boot into Recovery OS, erase your internal drive, then install the older macOS, then restore from a backup made prior to the recently applied upgrade. Even then, the firmware on the Mac may have been updated, meaning potential conflicts and a possible need for DFU mode and a Configurator revive/restore, which would need to be done via another Mac connected to yours. If that sounds complicated and risky, then you're assessing the situation correctly. Also note that in no case can you install a version of macOS that is earlier than the version installed on your Mac when it came out of the box. 

*Regarding the backup, if you want to pick up where you left off on the old version, you really need a backup made before the upgrade. If you do not have such a backup (why not?), then there are alternatives but you must be prepared to accept some work to get back to your normal. If you're in that situation, here are some strategies (and caveats):

• Manual file copying: Copy your most important files, folders, photos, and music to an external storage drive.
• Third-party backup software: Tools for backing up a Mac, such as SuperDuper or Carbon Copy Cloner can create a separate copy of your data. Do not assume that a clone created under the new major version of macOS will be bootable on your Mac.
• Cloud synchronization: Make sure cloud storage services such as iCloud, Dropbox, OneDrive, or Google Drive have finished synchronizing. Do not assume that every app’s data is stored in the cloud, as some applications store data only locally.
• Time Machine: If you have a Time Machine backup from before you upgraded to Golden Gate, you can use it to transfer compatible data after reinstalling Tahoe. When setting up the Mac from the backup, be sure to use a backup date from before you applied the major upgrade. You cannot restore from a backup made post-upgrade, and any changes since the upgrade will be lost. 

PhilKC wrote:

How can I downgrade back to MacOs 26?

[Re-Titled by Moderator]

Original Title: Golden Gate Sucks! I don't like it. I want out!

As has been pointed out this is not an easy task. If you are not skilled in the requirements to do it you’ll likely need to hire someone to do it for you. A better way might be to explain what issues you are having with macOS 27 and we might be able to help you sort things out.

You will find some very detailed steps here and some precautions to be aware of.

How do I downgrade my M2 Mac from golden … - Apple Community