How to Downgrade from macOS 12 Monterey to Big Sur

Downgrading from macOS 12 Monterey to macOS 11 Big Sur is a full wipe-and-reinstall process. You’ll erase your Mac’s drive, reinstall Big Sur, then restore your data from a backup. This guide covers both Intel and Apple Silicon Macs, with the exact steps for each. Before starting, back up your Mac with Time Machine or another method, and make sure you have a stable internet connection.

What You’ll Need

A full backup of your Mac (Time Machine or manual copy).
A USB flash drive (16GB or larger) if you want to create a bootable installer (optional but recommended).
Your Apple ID and password (to re-sign in after reinstall).
If using Apple Silicon: another Mac to create the bootable installer (optional).

Step-by-Step

Back up your Mac. Connect an external drive and use Time Machine (System Preferences > Time Machine) or manually copy important files. Verify the backup completes successfully.
Download the Big Sur installer. If you have a previous copy, use it. Otherwise, download from the App Store (search for “macOS Big Sur”) or use a direct link from Apple. If you’re on Apple Silicon, you can also use the erase method with macOS Recovery (see step 6).
Create a bootable installer (optional but recommended). On a Mac running any macOS, plug in a USB drive (at least 16GB, erased as Mac OS Extended Journaled). Open Terminal and run the command for your version, e.g., sudo /Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume. Replace MyVolume with your USB drive’s name. This may take 20-30 minutes.
Erase your Mac’s drive. Restart your Mac and immediately hold Command+R (Intel) or press and hold the power button (Apple Silicon) to enter Recovery. Use Disk Utility to erase the internal drive: select the drive (not the volume) and click Erase. Use format APFS (or Mac OS Extended Journaled for older Intel Macs) and GUID Partition Map scheme. Quit Disk Utility.
Install Big Sur. In Recovery, choose “Reinstall macOS” (or “Install macOS Big Sur” if you have the bootable installer). If using the USB installer, plug it in, restart while holding Option (Intel) or the power button (Apple Silicon), and select the USB drive. Follow the on-screen prompts, selecting your erased drive as the destination.
If you skipped the bootable installer (Apple Silicon only): In Recovery, you may see an option to “Install macOS Big Sur” only if you’ve previously downloaded it. Otherwise, you’ll need to use the USB method. For Intel Macs, you can use Internet Recovery (Command+Option+R) to reinstall the original macOS, then upgrade to Big Sur.
Set up your Mac. After installation, the Mac restarts. Go through the setup assistant. When asked, choose to migrate from your Time Machine backup or another drive. If you skip this, you can use Migration Assistant later.
Restore your data. If you didn’t migrate during setup, open Migration Assistant (in Utilities folder) and follow the prompts to transfer from your backup.

Common Mistakes

Not backing up before erasing – you lose everything.
Erasing the wrong drive – double-check the drive name in Disk Utility.
Using a USB drive that’s too small or not properly formatted.
Forgetting that Apple Silicon Macs require a bootable installer if you want to go to a specific older macOS version.
Interrupting the installation process (e.g., closing the lid or unplugging power).

Tips

Write down your Apple ID and password before starting.
If you have an Intel Mac, you can also downgrade by restoring from a Time Machine backup of a Big Sur system – but that’s only if you have one.
Keep the USB installer handy in case you need to reinstall again.
After downgrading, check that all your apps are compatible with Big Sur.
If you’re downgrading due to performance issues, consider a clean install without restoring everything – start fresh.

Troubleshooting

Installer says “macOS Big Sur is not available” – This usually means the installer is corrupted or the download didn’t complete. Re-download the installer and recreate the bootable USB.
Stuck on a loading screen or Apple logo – Force restart by holding the power button for 10 seconds, then try again. If it persists, boot into Recovery and use Disk Utility to repair the disk.
Cannot see the USB drive in Startup Manager – Ensure it’s properly formatted and plugged directly into the Mac (not a hub). On Apple Silicon, you may need to allow booting from external media in Startup Security Utility.
Migration Assistant doesn’t see your backup – Make sure the backup drive is connected and recognized. Try restarting the Mac and running Migration Assistant again.
Wi-Fi not working after downgrade – Reinstall the network drivers by updating to the latest Big Sur version via Software Update.
You see a message about a newer version of macOS already installed – This happens if you didn’t erase the drive properly. Go back to Disk Utility and erase again, ensuring you select the entire physical drive.

Frequently Asked Questions

Will I lose all my files?

Yes, the process erases your entire drive. You must back up before starting.

Can I downgrade without a USB drive?

On Intel Macs, you can use Internet Recovery (Command+Option+R) to reinstall the original macOS, then upgrade to Big Sur. On Apple Silicon, you’ll need a bootable installer for a specific version.

How long does the downgrade take?

It depends on your internet speed and Mac model. The download and installation can take 1-3 hours, plus time to restore your backup.

Can I go back to Monterey after downgrading?

Yes, you can upgrade again at any time via System Preferences > Software Update.

Do I need to erase my Mac if I have a Time Machine backup?

Yes, you must erase the drive to remove Monterey completely. You’ll then restore from the backup.

Will my apps work on Big Sur?

Most apps that work on Monterey also work on Big Sur, but some newer apps may require Monterey. Check compatibility with each app’s developer.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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