Bootable macOS Tahoe Installer and Clean Install

For clean installs of macOS or installs on multiple computers with only one download, creating a bootable macOS installer on a USB drive is the way to go.

Up to Sequoia, Apple released standalone installers for the major releases of macOS on the App Store. For Tahoe, however, there's no such thing and probably never will. The installer is available on third-party download sites, but it is an incredibly bad idea to use any of them, no matter how trustworthy it may look. Just don't do it!

Also, there's no reason to take such unnecessary risks – with a little help of the Terminal.

Create a Bootable USB macOS Installer

You'll need a big enough USB drive. Use the Disk Utility to erase it to HFS+ format and the default name /Volumes/Untitled. Then launch the Terminal and:

# Find the installer for the version of macOS you wish to install
softwareupdate --list-full-installers

# Download the installer app
softwareupdate --fetch-full-installer --full-installer-version {VERSION}

# Create a bootable installer on the USB drive:
sudo "/Applications/Install macOS {MACOS_NAME}.app/Contents/Resources/createinstallmedia" --volume /Volumes/Untitled

That's it, easy as 123 and free as in free beer!

Clean Install

I won't go into much detail here, but the basic steps are as follows:

1. Create a Time Machine backup.
2. Create a second, full backup using SuperDuper, Carbon Copy Cloner or a similar tool.
3. Make sure you have successfully completed the steps 1 and 2.
4. Attach the USB drive containing the installer.
5. Shut down your Mac, then restart it into boot options: On an Apple Silicon Mac, push and hold the power button. On an Intel Mac, push the power button, then hold the option key (⌥).
6. Use the Disk Utility to erase the startup disk to APFS.
7. Use the macOS installer on the USB drive to clean install macOS.
8. Migrate your data from one of the backups onto the fresh macOS.

(Image by Leehu Zysberg)