How to Clean Install MacOS Sequoia

A clean install of macOS Sequoia installs the operating system onto a freshly erased Mac, removing all existing data, settings, and even the previous MacOS versions from the Mac. This approach is sometimes preferred by advanced users who want a completely fresh start, are troubleshooting persistent system issues, or simply want to run MacOS Sequoia without any leftover files from an earlier installation. And, if you don’t mind starting from scratch with none of your files, apps, or data, you can even use a clean install of MacOS Sequoia as a way to downgrade a Mac from MacOS Tahoe.

The method we’re going to use here for performing a clean installation of MacOS Sequoia is by using a bootable USB installer drive, built specifically with the latest version of the MacOS Sequoia installer. After booting the Mac from the installer disk, you can erase the internal drive of the Mac, and then install MacOS Sequoia onto the newly formatted disk, giving you the fresh installation upon completion.

Before proceeding, remember that a clean install completely erases the Mac, that means all apps, photos, files, media, backups, the operating system – literally everything. If you have important files or data, be sure to create a full backup first, either manually or by using Time Machine or your backup method of choice.

MacOS Sequoia Clean Install Prerequisites

Before starting the clean install process, you’ll need the following:

• A 16GB or larger USB drive for creating a bootable MacOS Sequoia USB installer drive
• A compatible Mac capable of running MacOS Sequoia
• A full backup of your Mac (recommended, since the process erases all data)
• An active internet connection for activation and setup

If you have not yet created a bootable installer drive, you will need to download the macOS Sequoia installer and make a USB installer first. If you already have a bootable Sequoia installer, you can skip this next section.

Create a macOS Sequoia USB Boot Installer Disk

Before starting, you’ll need a USB flash drive with at least 16GB of storage. Remember that the USB drive will be completely erased during this process.

1. Download the latest version of the MacOS Sequoia installer file (or use this direct download link for 15.7.4)
2. Connect the USB drive to the Mac
3. Open the Terminal application from the /Applications/Utilities folder
4. Execute the following command in the Terminal, changing “MyUSB” to the name of your USB drive:

sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/MyUSB

5. Hit return and enter the admin password

The process of making a macOS Sequoia installer usually takes several minutes, depending on the speed of the drive.

When the command finishes, the USB drive will be renamed as “Install macOS Sequoia”, and it will be ready to use as a bootable installer disk.

How to Clean Install macOS Sequoia with a USB Installer

Performing a clean install involves booting the Mac from the installer drive, erasing the internal disk, and then installing macOS. Restart the Mac and follow the appropriate steps below, depending on if you have an Apple Silicon Mac, or an Intel Mac.

1. Connect the macOS Sequoia USB installer drive to the Mac
2. Restart the Mac
For Apple Silicon Macs:
• Immediately press and hold the Power button until the startup options screen appears

For Intel Macs:

• Immediately hold the Option (⌥) key during startup
3. When the boot menu appears, select the macOS Sequoia installer drive
4. Select Disk Utility from the macOS Utilities screen
5. Choose the internal drive that currently contains macOS
6. Click on Erase – Remember that this permanently deletes all data on the Mac
7. Select Apple File System (APFS) as the format
8. Click Erase to format the disk
9. When the disk is finished erasing, quit out of Disk Utility to return to the primary installer screen
10. Now choose “Install MacOS Sequoia” from the Utilities screen
11. Click on Continue and follow the on-screen instructions
12. Select the freshly erased internal drive as the installation destination

The Mac will begin installing macOS Sequoia. This process can take a while, and the Mac may restart several times during installation. When finished, the Mac will boot into a fresh installation of MacOS Sequoia.

If you do happen to have a Time Machine backup available that is compatible with MacOS Sequoia, then you’ll be able to restore your data from that Sequoia compatible backup if you’d like. You can use backups from older versions of MacOS than Sequoia, but not newer (meaning Tahoe backups will not restore to Sequoia). If you don’t restore from a backup, you can just set up MacOS Sequoia as if it were a new Mac.

Clean installing MacOS can be useful when troubleshooting stubborn system problems, preparing a Mac for a new user or owner, starting fresh with a different version of macOS, or even as a drastic downgrade approach if you aren’t happy with a newer version of MacOS like MacOS Tahoe.

Have you performed a clean install of macOS Sequoia? Did you use a USB installer drive or another method? Share your experience with the clean installation process in the comments.