How to Clean Install MacOS Catalina

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Some Mac users may wish to perform a clean install of MacOS Catalina onto a Mac. A clean install represents a fresh start, and it’s achieved by erasing all data from the Mac hard drive and then performing a fresh clean installation of MacOS Catalina onto that Mac. A clean install sort of feels like getting a new Mac in the sense that no data is on the device at all, there are no apps, no user accounts or user data, no system preferences or customizations, there is nothing left on the Mac at all, it’s just a blank new installation of MacOS Catalina.

Clean installs are not recommended for most Mac users and because the hard disk is erased it has potential to cause permanent data loss, so this is really only appropriate for advanced users with a compelling reason to format their Mac and start over, or if someone is selling a Mac or transferring ownership, or otherwise. Be sure you have a complete backup of your Mac and all important data made before proceeding.


A clean install of MacOS Catalina 10.15.x requires the following:

It’s important to remember that a clean install will erase all data and everything on the Mac. All personal data, apps, files, and anything on the Mac is erased in this process. Failure to have sufficient data backups may result in permanent data loss, so proceed at your own risk.

How to Clean Install MacOS Catalina

Warning: This erases everything on the Mac. Do not proceed unless you are comfortable removing all data and have backups made.

  1. Complete a full Time Machine backup before beginning – do not skip making a full backup
  2. Connect the MacOS Catalina installer drive to the Macs USB port
  3. Reboot the computer
  4. Immediately hold the OPTION key until the boot selection menu appears on the display, then choose the “Install MacOS Catalina” drive at the boot menu
  5. At the “macOS Utilities” screen, choose “Disk Utility”
  6. In Disk Utility, select “Macintosh HD” (or the name of the disk to erase and clean install Catalina onto), then click the “Erase” button
  7. Erase the Mac drive to clean install MacOS Catalina

  8. Choose “Macintosh HD” as the name, then go to “Format” and select APFS, then choose “Erase” – WARNING: THIS ERASES ALL DATA ON THE MAC
  9. Quit Disk Utility when finished formatting the disk
  10. At the ‘macOS Utilities’ screen again, select “Install macOS” from the options
  11. How to clean install MacOS Catalina

  12. Select “Macintosh HD” as the destination to install MacOS Catalina, then choose “Install” to begin clean installing MacOS Catalina

This will begin the process of clean installing MacOS Catalina onto the Mac, it may take a while to complete. The Mac will reboot itself automatically during the process, let it finish and do not interrupt the installation.

After the clean install of Catalina has completed, the Mac will boot back into a fresh and new installation fo MacOS Catalina, similar to getting a new computer and turning it on the first time.

Mac Catalina desktop

Because the Mac was erased during this process, there will be no personal files, no apps, no preferences, no settings, no customizations whatsoever on the Mac, it will be as if it is new, which is why this is colloquially called a “clean install” in the tech world.

The Mac will basically appear as if it’s new at this point, and you’re free to either restore data to it from backups, or to start fresh without restoring or copying any anything to the computer again.

Some users may opt to perform a clean install as a troubleshooting method if they experienced frequent issues with their system software. Nonetheless if you are encountering problems with MacOS Catalina, check out this troubleshooting guide for help addressing macOS Catalina problems.

Were you able to successfully perform a clean install of MacOS Catalina? Do you use another approach to clean install Catalina? Let us know your experiences and thoughts in the comments.

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, OS X Daily reports

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