How to do a clean install of macOS 11 Big Sur

clean install macOS 11 Big Sur - hero image

Power users usually prefer to start a fresh new installation of Big Sur rather than upgrade the existing copy of the macOS operating system on their Mac. If you’re among them, you’ll need to perform a clean install of Big Sur. The process entails doings things such as backing up your Mac, wiping off the current operating system and creating a bootable installer. Follow this tutorial for detailed instructions on how to perform a clean install of macOS Big Sur.

Big Sur brings tons of goodies

macOS 11 Big Sur is a major software update from Apple that brings many, many new features and improvements to any compatible Mac computers. You’ll instantly notice that the visuals have been refined while app icons have been redesigned to be more eye-catching.

Control Center on MacBook Pro with Big Sur
With macOS Big Sur, you can take advantage of a neat Control Center on your Mac

You’ll enjoy the biggest Safari update ever, discover new features for Maps and Messages, use a Control Center for the first time on your Mac, get even more transparency around your privacy and much, much more. Apple released Big Sur to the public on November 12, 2020.

System requirements for macOS Big Sur

To install macOS Big Sur, be sure that your Mac meets the minimum system requirements. For reference, macOS 11 Big Sur is compatible with the following Mac computer models:

  • MacBook (2015 or later)
  • MacBook Air (2013 or later)
  • MacBook Pro (late 2013 or later)
  • Mac mini (2014 or later)
  • iMac (2014 or later)
  • iMac Pro
  • Mac Pro (2013 or later)

The complete list of compatible Macs is available on Apple’s website.

Clean install vs. upgrade

One of the dilemmas that more advanced Mac users typically face is whether to upgrade their existing macOS installation to Big Sur or perform a fresh install. Each method — and this tutorial covers them both — has its benefits and drawbacks.

  • Upgrade: Updates the existing macOS operating system and any settings to Big Sur through the Mac App Store, keeping your files intact. This is the most convenient method for many people  because it uses the familiar Software Update mechanism and retains all your saved settings, apps and files on a new system.
  • Clean install: Installs a copy of Big Sur on a freshly formatted volume, without keeping any of your locally-saved files. This requires creating a bootable installer that you’ll boot into when starting up your Mac and wiping your startup drive clean.

Pro users are recommended to start anew by performing a clean install. Should you decide to go down that route, you will need to back up and restore your personal files in order to avoid losing important documents. However, you’ll gain a lot in terms of user convenience.

Notification Center on MacBook Pro with Big Sur
Big Sur merges your Notification Center and Today widgets into one view

Oftentimes old files and the cruft accumulated from previous installations get carried over when you upgrade your current macOS version. A clean install will make your Mac run faster and fix common issues such as unexpected freezes, slowdowns and so forth.

How to do a clean install of macOS 11 Big Sur

As I mentioned earlier, performing a clean install of macOS 11 is a multi-step process that’s more complex than simply erasing your startup drive, installing Big Sur and calling it a day.

Here’s what you’ll need to do:

Let’s get on with it.

Create a backup of your Mac

You will need to use an external disk paired with Apple’s Time Machine backup feature, which is built into your Mac, in order to safely back up everything on your Mac.

  1. Connect an external storage device to your Mac.
  2. Click the Apple menu, then choose the option “System Preferences”.
  3. In the System Preferences window, click “Time Machine”.
  4. Click the button “Select Backup Disk”.
  5. Select your backup disk from the list of available disks, then click “Use Disk”.
  6. Choose the option “Back Up Now” from the Time Machine menu in the macOS menu bar.

The first backup may take a long time, depending on the size of your startup disk and your Mac model, but you can continue using your computer while a backup is underway.

clean install macOS 11 Big Sur - choosing a backup disk for Time Capsule

Now, you may also use other methods to back up your important files. With iCloud Photos, for instance, all your photos and videos can be stored in iCloud. With iCloud Drive, you can store personal files, such as your photos, documents and music, in the cloud.

How to move your Mac user folder to a separate drive from the boot drive

If I had to give you a word of advice, it would be to avoid using Time Machine for cloning your Mac’s startup drive. First of all, Time Machine only backs up files and doesn’t do bootable backups. As a result, you may encounter various annoying issues should you later decide to roll back to an earlier macOS installation from a Time Machine backup. Another problem with Time Machine is its tendency to carry over various macOS issues into new installations.

How to restore individual files using Time Machine

If you follow my advice, you’ll want to use a third-party solution to create a bootable clone of your drive. The longstanding Carbon Copy Cloner app from Bombich Software, a $40 value, is probably the best utility to do a complete, bootable backup of your Mac. With it, you can easily downgrade to a previous macOS version should you decide that Big Sur isn’t your cup of tea.

Carbon Copy Cloner on a MacBook Pro
Easily clone your Mac’s startup drive to a bootable volume with Carbon Copy Cloner

Another recommended backup software is Get Backup Pro from BeLight Software, priced at $20, which is one of the most versatile alternatives to Time Machine. Similar to Carbon Copy Cloner, this app lets you create a bootable clone of your Mac’s startup drive, restore from the backup file to another drive, schedule your backups, back up only specific files and so forth.

It’s available at no charge via Setapp, a subscription service for quality macOS/iOS apps.

Download the Big Sur installer

Before you can create a bootable installer for macOS Big Sur, you’ll actually need the full installer which can be downloaded for free from the Mac App Store.

  1. Open the Safari browser on your Mac.
  2. Click this link to land on the Big Sur page in the Mac App Store.
  3. Once in the Mac App Store, click the “Get” button or the iCloud download icon.
  4. Click “Download” to confirm the operation.

This’ll cause Software Update to download the latest version of Big Sur to your computer.

The Big Sur page on the Mac App Store

After downloading, the installer shall automatically open. Unless you’ve changed your mind and want to upgrade rather than perform a clean install, don’t click “Continue”.

How to fix Big Sur installation errors on older MacBook Pros

What you want to do instead is quit the installer by choosing “Quit Install macOS” from its menu or pressing the Command (⌘) + Q combination on your keyboard. Don’t worry, the installer still lives in your Mac’s Applications folder as an app named “Install macOS Big”. We’re now going to use it to create a bootable USB installer for macOS Big Sur.

Erase your USB drive

Be sure that your USB drive or other volume has at least twelve gigabytes of available storage and is formatted as macOS Extended using the built-in Disk Utility app.

  1. Launch Disk Utility from the Applications/Utilities folder on your Mac.
  2. Select your USB drive from the list of internal drives in the lefthand column.
  3. Click the text field next to “Name,” then type “Untitled” as the new drive name.
  4. Click the popup menu next to “Format” and set the drive format to “Mac OS Extended”.
  5. Click “Erase” to erase the drive using the above parameters.
  6. Click “Done” after the disk has been successfully formatted.

You now have a properly formatted USB drive to put a bootable Big Sur installer onto.

clean install macOS 11 Big Sur - erasing USB disk

You’ll use the bootable installer on this drive later to clean-install macOS Big Sur.

Create a bootable USB installer

With your USB drive properly formatted with the “Mac OS Extended” option, let’s create a bootable installer that you’ll boot into later to perform a clean install of Big Sur.

  1. Launch Disk Utility from the Applications/Utilities folder on your Mac.
  2. Select your USB drive from the list of internal drives in the lefthand column.
  3. Click the text field next to “Name,” then type “Untitled” as the new drive name.
  4. Click the popup menu next to “Format” and set the drive format to “Mac OS Extended”.
  5. Click “Erase” to wipe the drive clean using the above parameters.
  6. Click “Done” after the disk has been successfully formatted.
  7. Now open Terminal, which is in the Utilities folder of your Applications folder.
  8. Type or paste this line in the Terminal window, then press Enter:

sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled

If asked, type your Mac’s administrative password to continue. Because this command will delete all files on your USB drive, you’ll be asked to type “Y” to confirm the operation. The command will now create a bootable Big Sur installer on your USB drive.

clean install macOS 11 Big Sur - creating bootable installer in Terminal

The process can take about 30 minutes to complete so grab yourself a quick snack while you’re waiting. Keep in mind that the above command makes two crucial assumptions. Firstly, your destination drive must be Mac-formatted. And secondly, the name of the drive must be “Untitled” or the above command won’t work (pro users, don’t worry, you can easily replace “Untitled” in the above command with your custom drive name).

You can now quit Terminal and eject the volume.

Perform a clean install of Big Sur

You will need to restart your computer and hold down a special key to bring up the startup volume selector, then choose your bootable Big Sur installer to start up your Mac from.

  1. Plug the bootable USB installer into your Mac.
  2. Click the Apple menu and choose the option “Shut Down”.
  3. If your Mac uses Apple Silicon, turn it on and continue holding the power button until you see the startup options window. If your Mac uses Intel, press and hold the Option (⌥) key immediately after turning it on, then let go when you see a list of bootable volumes.
  4. On your Apple Silicon Mac, select the volume containing the bootable installer, then click “Continue”. On an Intel-based Mac, select the USB volume containing the bootable installer and click the Up arrow or press Return on the keyboard.
  5. When the Big Sur installer opens, click “Continue” and follow the onscreen instructions.

You may be asked to choose your language. As part of the setup process, you may also be offered to customize your settings, enable Siri, provide your iCloud credentials and so forth. If you can’t start up from the bootable installer on your Mac with Apple’s Security chip, you must set the External Boot setting in Startup Security Utility to allow booting from external media.

clean install macOS 11 Big Sur - installer splash screen

It’s important to note that your bootable Big Sur installer requires an Internet connection to get firmware and other information specific to the Mac model you have.

How to upgrade your macOS version to Big Sur

If you don’t want to do a clean install and would rather update your existing macOS version to continue right where you left off, you’ll need to get macOS Big Sur via Software Update.

  1. Click the Apple menu, then choose the option “System Preferences”.
  2. In the System Preferences window, click “Software Update”.
  3. When the macOS Big Sur update appears, click the “Update Now” button to download it.
  4. When the Big Sur installer opens, click “Continue” and follow the onscreen instructions.

You might be asked to enter your administrator password.

clean install macOS 11 Big Sur - Software Update showing the macOS Big Sur update

The macOS Big Sur installer will update your copy of macOS on this Mac, retaining all your settings, files, documents, apps and so forth. One moment you’re in Catalina and after around 45 minutes — boom, just like that and you’re in Big Sur and all your stuff is just there!

Apple cautions:

Please allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart, show a progress bar or show a blank screen several times as it installs both macOS and related updates to your Mac firmware.

You don’t need a bootable installer to upgrade macOS.

How to reinstall macOS Big Sur

Reinstalling macOS Big Sur basically creates a new copy of the operating system on your Mac, which is useful when your computer refuses to boot or shows critical errors. To reinstall Big Sure, you’ll need to start up your computer in macOS Recovery mode.

  1. If you have an Apple Silicon Mac, turn it on by pressing and holding the power button until you see the startup options window. On Intel Macs, turn on the machine and immediately press and hold the Command (⌘)-R key combination until you see an Apple logo or other image.
  2. On your Apple Silicon Mac, click a gear icon labeled “Options,” then click “Continue”. On your Intel Mac, select a macOS user account and click “Next”, then enter its administrator password.
  3. Once you see the macOS Recovery screen, click “Reinstall macOS”, then choose “Continue”.
  4. Follow the installer’s instructions to finish reinstalling Big Sur.

If the installer asks to unlock your disk, enter the password you use to log in to your Mac. You’ll be asked to choose a disk on which to install the operating system. If you need to erase the disk before installing Big Sur, select Disk Utility from the Utilities window in macOS Recovery.

clean install macOS 11 Big Sur - The Reinstall macOS Big Sur option in macOS Recovery

macOS Recovery installs the latest macOS version that was previously installed on your Mac, with some exceptions that Apple highlights in a support document:

If you just had your Mac logic board replaced during a repair, macOS Recovery might offer only the latest macOS compatible with your Mac. If you erased your entire disk instead of just the startup volume on that disk, macOS Recovery might offer only the macOS that came with your Mac or the closest version still available.

You can get other macOS versions using macOS Recovery, too.

To do so, simply turn on your computer and immediately press and hold Option (⌥)-Command (⌘)-R to upgrade to the latest macOS that is compatible with your Mac. Or, you can press and hold the Shift(⇧)-Option(⌥)-Command(⌘)-R keyboard combination to reinstall the macOS that came with your Mac or the closest version that’s still available.

Hope you enjoy Big Sur as much as we do!