Want to perform a clean installation of macOS Monterey (or any MAC) on your Mac? Here’s how to download and install a new copy of each of Apple’s operating system versions for laptops and desktops (Monterey, Catalina, Mojave, High Sierra, El Capitan, or Yosemite).

How to do a clean installation of macOS

The new version of Apple’s macOS Monterey operating system is already official since October 25, 2021, so you can proceed with the installation if you have a compatible computer.

There are many advantages provided by the new system, related to FaceTime, the renewed design of the Safari browser, and new features associated with its interface with functions of ‘Universal Control‘ and ‘Shortcuts.’

Should you do a simple system update, or is it better to do a new and clean installation? This article explains how to perform a clean installation of macOS, the recommendation if you do not want to drag duplicate files or background processes.

Professionals emphasize that it is a more advantageous option in cases where the Mac has become slower or behaves strangely, hanging with the execution of specific applications or slowing down the performance of certain tasks.

We usually resort to whenever we think that the computer may have a virus (although there is a lot of debate about whether there are viruses and malware on the Mac that can cause the operating system to malfunction).

Let’s start by showing step by step how to do it for the latest versions of macOS (Monterey at the time of writing), before showing how to install a clean copy of an older version such as Catalina, High Sierra, Sierra, El Capitan, Mojave, Yosemite or some previous version of OS X.

What tools do I need?

Before you begin, you should know two ways to perform a clean installation on macOS. The traditional way was to make a bootable copy of the macOS installer on a flash drive and then format your drive before installing the boot copy on your Mac.

An even more straightforward method allows you to use macOS Recovery to reinstall the Mac operating system from the web. It’s something we’ll also look at throughout the article.

A word of warning, if you want to perform a clean installation of macOS Monterey or Catalina and you’re already running any of them, the process is different than previous versions of macOS. You will now find two volumes to remove: Macintosh HD-Data and Macintosh HD. We’ll explain what you need to do about it.

How to do a clean installation of macOS using a bootable USB

Before you begin, you’ll need the following:

  • A removable USB flash drive of at least 15 GB or more to save the installer file of our chosen version of macOS. We are going to delete it from the system, so we recommend that you make sure that you do not have any valuable data.
  • Administrator privileges for Mac
  • Make a backup so that in case something goes wrong, you can go back to a previous version of the system. Use this guide: How to Backup a Mac in Simple Steps

Regarding backups, you probably don’t want to recover a Time Machine backup if you don’t want to copy all the settings and preferences associated with your previous system.

Alternatively, you can sync all your documents and desktop to iCloud instead of running a full backup, but make sure everything you need is in the cloud and keep in mind that you may lose system settings and app installation.

Are you ready? Started

Step 1: Format the external drive

How to do a clean installation of macOS

We will re-download the installer file of our chosen version of macOS and store it on a USB stick or external drive. The Pendrive you use will need to be formatted as a macOS Extended volume with a GUID partition table.

Here’s how to format your USB drive correctly:

  1. Plug in the USB drive
  2. Go to Applications> Utilities
  3. Open System Disk Utility
  4. Select the drive and click Erase. (The disk name should be ‘Unnamed‘ if the following Terminal commands work, so rename if necessary.)
  5. Select macOS Extended (Journaled) as the format type.
  6. Choose the GUID partition map from the schema options. If you don’t see these options, you’d be in the wrong place. You should select the external drive, not the container under it.
  7. Click Erase.
  8. Disk Utility will create the partition and configure the drive (it may take time).
  9. Click Done and you’ll have it.

Step 2a: Get the macOS Monterey installation file

How to do a clean installation of macOS

If you’re reinstalling the latest version of macOS, or you’re installing a new version of macOS, the next step is relatively easy. However, the process for getting the installer will be different.

Suppose you are running Mojave and want to perform a clean installation of macOS Catalina. In that case, you can download the installation package through ‘System Preferences,’ the same will apply if you are running Catalina and want to perform a clean installation of Big Sur (once it starts):

  1. Open system preferences.
  2. Choose ‘Software Update‘.
  3. Download the macOS files.

If you want to install Monterey or Catalina and are already running the operating system, the best way to access the installer is through the Mac App Store. Here’s a direct link, but alternatively, open the Mac App Store and search for Monterey.

Once you’ve located Monterey on the Mac App Store, follow these instructions:

  1. Tap ‘Download or Get‘ (depending on the version of the Mac App Store you’re using).
  2. You may receive a warning message at this time, telling you that this version of macOS’ is already installed on this computer. Would you like to continue?’ Click Continue.
  3. Enter your Apple ID and password.
  4. The Monterey installation files will begin downloading.

The installation file will have several GB (Mojave had 5.7 GB, for example), so the download may take a while.

  1. When the macOS installer has finished downloading, the installer will start automatically, but we don’t want to use it yet, so don’t click start the installation yet.
  2. Press Command-Q to exit the installer
  3. Look for the installer file (it will be located in your Applications folder, or you can search for it using Spotlight (command ‘space and start typing Catalina or Big Sur, depending on your case).

If you want to install Monterey or Catalina, you can skip the next step, where we’ll show you how to dig up the installer file for an older version of macOS or macOS X.

Step 2b: Get the installation file for an older version of macOS

How to do a clean installation of macOS

For older versions of macOS and Mac OS X, it’s a little harder to get the installation file: Apple doesn’t offer downloads of outdated operating system versions through the regular store. Searching for the name, you won’t find what you’re looking for.

Depending on the version of macOS you’re running, installers for some macOS versions can be found in the ‘Purchased’ section of the App Store.

Try signing in to the Mac App Store with the Apple ID you used and click ‘Purchased’ in the menu bar at the top. Scan the list of apps you’ve purchased or downloaded for free and find the name of your chosen version. Click download.

There are a few reasons why it may not work for you:

  1. If you’ve already installed Mojave or Catalina on your Mac, you won’t be able to easily search for older versions of macOS from the Mac App Store.
  2. You won’t find the version of macOS your Mac shipped with in the ‘Purchased’ section of the App Store.
  3. You also won’t find versions of macOS in the purchased section if you’ve never installed that version.

Fortunately, it’s still possible to get some versions of macOS if you’re running a newer version than Sierra.

As in the previous step, once you have downloaded the installer, do not run it. Close the installer if it opens.

Step 3: Create a bootable USB disk

How to do a clean installation of macOS

Next, we must create a bootable Pendrive to install a new copy of macOS on your Mac from the USB. Let’s create the boot drive with Terminal, which you can open by pressing ‘Command + Spacebar’ and typing ‘Terminal.’

USB or installation pendrive

Connect the removable drive to your Mac and make sure it has the same name you named it after you created it.

Create a bootable USB disk with Terminal

Open the ‘Terminal’ app on your Mac using the ‘Command + Spacebar’ key combination and type the word Terminal.

Command Line - macOS Terminal

Now copy and paste the following text into Terminal (command line):

sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia –volume /Volumes/Untitled — /Applications/Install\ macOS\ Mojave.app

Press ‘Enter

Enter your password (you won’t see it appear). When the boot drive is ready, you’ll see the word Done. It may take some time. Be patient.

You can also use this guide: How to Create macOS Mojave Bootable Installer for Clean Installation: 2 Easy Steps (MAC only)

How to Create an Installation Bootable Drive for macOS 12 Monterey

How to install from a DVD drive

Finally, we will teach you how to install a copy of macOS from a drive or disk drive.

With the boot drive connected, start or restart your Mac while holding down the Option key (also known as Alt). This will take you to the ‘Admin‘ home screen. Choose to install the macOS version from the external drive.

Select ‘Disk Utility‘ and the disk on which it will be installed. It will be deleted. Go back to the main menu and choose Install macOS.

MacBook with macOS

Once the installation is complete, you can restore apps and other settings from the backup you created or download them manually.

Remember not to recover a Time Machine backup if it is a different operating system version not to copy all associated settings and preferences.

Step 4: Clean your Mac and install macOS

macBook macOS installation

We are now ready to install the copy of macOS from the installation drive on our Mac. If you want to perform a new installation (and completely erase your Mac), it’s time to reformat your Mac’s startup drive.

Here’s how to do a new macOS installation if you’re not already running Monterey:

  1. Connect your bootable drive.
  2. Start or restart your Mac while holding down the ‘Option‘ (Alt) key. This will take you to the ‘Startup Manager‘.
  3. Choose to install your chosen version of macOS from the external drive.
  4. Select ‘Disk Utility‘.
  5. Select the startup disk of your Mac, probably the so-called Macintosh HD or Home.
  6. Click ‘Erase‘.
  7. Wait for your startup disk to format
  8. Go back to the main menu of ‘Utilities‘ and choose ‘Install macOS‘.
  9. Choose your home drive as the location to install macOS

Once the installation is complete, you can restore apps and settings from your backup or manually download them.

How to do a clean installation of macOS
Author

Ruby has been a writer and author for a while, and her content appears all across the tech world, from within ReadWrite, BusinessMagazine, ThriveGlobal, etc.

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