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Apple today released macOS 12 Monterey, and whenever a new operating system is released for the Mac, some users prefer to perform a clean installation. This article explains how to perform what is effectively a clean install of Monterey using a brand new option that's available on Apple silicon-powered Macs and Intel Macs with a T2 security chip.

Monterey-Mac-as-External-Monitor-Feature.jpg

Clean installing macOS is often done to remove annoying quirks and strange behaviors that a Mac may have inherited over time, and can also help to reclaim disk space caused by junk files left by third-party apps. However, even if neither of these issues have arisen for you, sometimes it's just nice to start afresh for that "brand new Mac" feeling and then migrate your apps, documents, and data, either manually, or by migrating from a Time Machine backup.

Clean installing previous versions of macOS usually involves creating a bootable copy of the macOS installer on a flash drive or USB stick and then reformatting your drive before installing the bootable copy on your Mac, or using macOS Recovery to reinstall the Mac operating system over an internet connection. In Monterey, however, a third option has come into play on newer Macs that offers a very simple and straightforward way to erase your Mac without needing to reinstall the operating system.

Following in the footsteps of the iPhone and iPad, Apple silicon Macs and Intel Macs with a T2 security chip (2017-2020 models) now have an "Erase All Content and Settings" option available in macOS Monterey. Because storage is always encrypted on Mac systems with Apple silicon or the T2 chip, the system is instantly and securely "erased" by destroying the encryption keys.

erase-content-settings-monterey.jpg

Not only does this effectively erase all user data and user-installed apps from your Mac without reinstalling macOS, it also signs out your Apple ID, removes your Touch ID fingerprints, purchases, and all Apple Wallet items, and turns off Find My and Activation Lock, making it far easier to restore your Mac to like-new factory settings.

This ability means you can simply download and install macOS Monterey over your current macOS version when prompted, and then select the new erase function in Monterey, which will erase your Mac and leave the core macOS system intact. After erasing the Mac, it will display the Setup Assistant and be ready to be set up like new. You can then migrate your data manually or by using the Setup Assistant's migration option. The following walkthrough breaks down the steps involved.

  1. Before you do anything else, back up your data using Time Machine or your preferred backup method.
  2. In macOS, click the Apple () symbol in the menu bar and select System Preferences.
  3. Click Software Update in the preferences pane.
    software-update.jpg

    Allow Software Update to ping Apple's servers, then click Upgrade Now to download the Monterey installer when it appears. You can continue to use your Mac while the installer is being downloaded. Once the installer has downloaded, you'll receive a prompt. Click to install the new version of macOS and wait for the installation to complete.
    monterey-software-update.jpg

    Once your Mac has restarted into Monterey, click the Apple () symbol in the menu bar and select System Preferences....
  4. When the preferences pane appears, select System Preferences -> Erase All Content and Settings from the menu bar.
    erase-content-settings-macos.jpg

    Enter your admin password in the Erase Assistant dialog prompt and click OK.
  5. Note all the settings, data, media, and other items that will be removed. Click Continue if you're sure.
    erase-content-settings-monterey.jpg

    Click to sign out of your Apple ID, then click Erase All Content & Settings in the prompt to confirm.
    erase-content-settings-monterey-confirm.jpg

    Allow the erase process to complete. Your Mac may restart more than once during the process, after which you may be prompted to activate your Mac over Wi-Fi.
    Once finished, you'll see the "hello" message on your Mac's screen, indicating the Setup Assistant is ready. Follow the onscreen instructions, and if desired, elect to migrate your data from a Time Machine backup when the option appears.
    hello-macos-monterey-setup-assistant.jpg
That's all there is to it. Even if you're not clean installing Monterey today, the new option makes it far more convenient to restore your Mac to factory settings, whether you simply want to start afresh with your Mac in future or plan to sell or gift it to another person.

Article Link: How to Clean Install macOS Monterey Easily Using the New Erase Mac Option
 
Last edited:

siddavis

macrumors 6502a
Feb 23, 2009
638
1,833
I was so excited reading the headline, but then my hopes were dashed since I have a 2015 iMac. I have some quirks that I'd like to try and get rid of by doing a clean install, so I guess it's the old-school method for me. If they release that iMac with M2 or M1 Pro/Max (and space gray please!), then I'll leave the old-school method behind!
 

Lounge vibes 05

macrumors 68020
May 30, 2016
2,124
6,783
Extremely glad they finally added this.
I just got my M1 MacBook Air back in March though, so decided to just upgrade.
Do wonder if a full erase would fix my battery preference pane though, I still can’t change any of the settings.
 
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nortonandreev

macrumors 68020
Jan 11, 2016
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2,751
Manchester, United Kingdom
This is not really a clean install, to be fair. You might end up in the same state, settings and user created files wise, but I’m not sure it’s an equivalent of formatting a partition and installing macOS on it from scratch.

Regardless, this is not Windows, so this should be more than enough.
 
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kalsta

macrumors 68000
May 17, 2010
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Australia
Clean installing macOS is often done to remove annoying quirks and strange behaviors that a Mac may have inherited over time, and can also help to reclaim disk space caused by junk files left by third-party apps. However, even if neither of these issues have arisen for you, sometimes it's just nice to start afresh for that "brand new Mac" feeling and then migrate your apps, documents, and data, either manually, or by migrating from a Time Machine backup.
Good luck with that. Migrating from a Time Machine backup will restore your Library folder, along with all those 'junk files' you just got rid of. A real clean install is not for the faint-hearted! I've done it several times over the years and should probably write a book about it. Possibly worth it if your Mac is behaving poorly. Definitely not worth it for 'that "brand new Mac" feeling'.
 

kalsta

macrumors 68000
May 17, 2010
1,672
527
Australia
I was so excited reading the headline, but then my hopes were dashed since I have a 2015 iMac. I have some quirks that I'd like to try and get rid of by doing a clean install, so I guess it's the old-school method for me. If they release that iMac with M2 or M1 Pro/Max (and space gray please!), then I'll leave the old-school method behind!
Erasing macOS was never the hard bit. Sure, the real 'old-school method' of creating a bootable installer was a little bit of effort, but installing from macOS Recovery is a doddle. See How to reinstall macOS. The hard bit is restoring your Mac to the way you like it without copying over all the old Library files.
 

E__F__

macrumors newbie
Mar 27, 2021
8
1
Chicago
Will this also erase the bootcamp partition or does it just erase and reinstall the macOS partition?
 

James Godfrey

macrumors 68000
Oct 13, 2011
1,754
1,320
Now this way of erasing a Mac is available, is the old way of booting into recovery erasing your drive and reinstalling Mac OS still possible or is that a thing of the past now???
 
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msackey

macrumors 6502a
Oct 8, 2020
547
426
Alas, I don't have this because my computer has a T1 chip instead of a T2 or above.

Curious to know why computers with a T1 chip don't have this option. Would love to read up on that.
 

Lounge vibes 05

macrumors 68020
May 30, 2016
2,124
6,783
This is not really a clean install, to be fair. You might end up in the same state, settings and user created files wise, but I’m not sure it’s an equivalent of formatting a partition and installing macOS on it from scratch.

Regardless, this is not Windows, so this should be more than enough.
Well, given that everything is erased other than the system partition, and system files by default haven’t been able to be modified by the user since 2015, 99.9% of the time if you’re having issues, slow-downs, lag, faulty Applications, etc, erasing everything on the petition that can be modified by the user will solve those issues.
Just like iOS, it’s very, very rare that recovery mode is actually necessary anymore for trouble-shooting for the regular consumer.
 

Mr. Dee

macrumors 601
Dec 4, 2003
4,291
7,542
Jamaica
We’ve come a far way from installing OS X from a CD. I had restored from a Time Machine backup of my Early 2015 to my MBP M1 and noticed there has been an issue with Office 365 since I keep getting promoted to enter a credential for Word or PowerPoint. It doesn’t happen with Excel or Outlook. If I persistently click Ignore it will disappear. But I ‘be hardly used Word on my M1.

Just don’t want to go through the hassle of reinstalling macOS though. Maybe I should by a new 2021 MacBook Pro to justify it. ?
 
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kingtj1971

macrumors 6502
Feb 11, 2021
312
298
Alton, IL
We’ve come a far way from installing OS X from a CD. I had restored from a Time Machine backup of my Early 2015 to my MBP M1 and noticed there has been an issue with Office 365 since I keep getting promoted to enter a credential for Word or PowerPoint. It doesn’t happen with Excel or Outlook. If I persistently click Ignore it will disappear. But I ‘be hardly used Word on my M1.

Just don’t want to go through the hassle of reinstalling macOS though. Maybe I should by a new 2021 MacBook Pro to justify it. ?

That's a known issue with Office on the Mac, actually. Usually a keychain related issue.

  1. Quit all Office applications (Word, Teams, Outlook, etc)
  2. Go to KeyChain Access.
  3. Search "Exchange" under Login --> All Items and delete everything.
  4. Search "Office" and delete everything.
  5. Search "ADAL" and delete everything.
  6. Launch Outlook.
  7. You will get the activation prompt and then If account is already added you will see the password prompt for app and ADAL again. Please do 2-Factor Authentication if asked to.
  8. If that doesn't work, do steps 2-4 but restart the Mac before launching Outlook.
 

James Godfrey

macrumors 68000
Oct 13, 2011
1,754
1,320
I do this with every Major OS update and seem to never get those “unique” quirky issues that others complain about… Bluetooth, display sleep/connection, audio, etc.
Same, used to do it with my iPhone too, but can’t be bothered these days. I do find though all OS’s run smoother on a fresh install.
 
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cult hero

macrumors 65816
Jun 6, 2005
1,156
972
This is a nice feature. I've sold many, many Macs (mine and those for family) and purchased even more directly or indirectly. It's not the hardest thing in the world but... it's still rather annoying.

The other nice thing is some of the time machines were brought to me for that purpose because I'm the "tech guy." Between this and Time Machine, someone like my dad could do a migration for the most part—even if I was just assisting a little over the phone.
 
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Mr. Dee

macrumors 601
Dec 4, 2003
4,291
7,542
Jamaica
That's a known issue with Office on the Mac, actually. Usually a keychain related issue.

  1. Quit all Office applications (Word, Teams, Outlook, etc)
  2. Go to KeyChain Access.
  3. Search "Exchange" under Login --> All Items and delete everything.
  4. Search "Office" and delete everything.
  5. Search "ADAL" and delete everything.
  6. Launch Outlook.
  7. You will get the activation prompt and then If account is already added you will see the password prompt for app and ADAL again. Please do 2-Factor Authentication if asked to.
  8. If that doesn't work, do steps 2-4 but restart the Mac before launching Outlook.
Thanks, will try this first thing when I get home!
 

kagharaht

macrumors 6502a
Oct 7, 2007
984
435
I must be getting old. To me Clean Install is basically wiping the drive and reinstalling Mac OS for DISK, Another bootable external volume or Net Boot, Shift options command R. Am i right or just a ghost in the past. lol
 

TriBruin

macrumors 6502
Jul 28, 2008
352
747
This is not really a clean install, to be fair. You might end up in the same state, settings and user created files wise, but I’m not sure it’s an equivalent of formatting a partition and installing macOS on it from scratch.

Regardless, this is not Windows, so this should be more than enough.
Nope, this is a clean install. NOTHING related to the user is left on the drive. The reason this works is that starting with Catalina, Apple split the O/S volume from the Data volume. With Big Sur, Apple took one stop further and has cryptographically signed the O/S volume to prevent modification. In addition, during regular operation, the system volume is copied to a disk image and run from there. You are never running the system directly from the O/S volume.

Erasing the drive clears the encryption keys for the data volume, rendering it unusable. The system then recreates the data volume and activates the O/S.
 

Apple_Robert

Contributor
Sep 21, 2012
31,123
41,759
In the middle of several books.
I must be getting old. To me Clean Install is basically wiping the drive and reinstalling Mac OS for DISK, Another bootable external volume or Net Boot, Shift options command R. Am i right or just a ghost in the past. lol
I am used to old school as well. Monterey changed that for me and I am so glad I don't have to do the old school route any more.
 

Shirasaki

macrumors G5
May 16, 2015
13,438
7,703
Haven’t found macOS Monterey on App Store yet. Forced to get the installer elsewhere.

With that being said, is it even possible to “format the internal drive” anymore? I’d like to erase everything and restore from backup (yeah the old school way). Maybe I should give it a shot, just that I need to backup without using time machine. Backup migration to another disk is impossible and I hate that.

Within next release or so, I reckon Apple May remove recovery options and partitions entirely, so that user can no longer “reduce system security level” to install other stuff that is not approved by Apple.
 

Apple_Robert

Contributor
Sep 21, 2012
31,123
41,759
In the middle of several books.
Haven’t found macOS Monterey on App Store yet. Forced to get the installer elsewhere.

With that being said, is it even possible to “format the internal drive” anymore? I’d like to erase everything and restore from backup (yeah the old school way). Maybe I should give it a shot, just that I need to backup without using time machine. Backup migration to another disk is impossible and I hate that.

Within next release or so, I reckon Apple May remove recovery options and partitions entirely, so that user can no longer “reduce system security level” to install other stuff that is not approved by Apple.
It's on the App Store. I used it today after I installed Monterey and made a USB installer. Type in macOS Monterey
 

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