Let macOS Sierra install, the entire installation process can take a while so be prepared to wait.

Click on “Continue” and agree to the terms, then select “Macintosh HD” (or the target drive name) from the drive list and then choose “Install”.Choose “Install macOS Sierra” from the menu options.After the drive is finished formatting, quit out of Disk Utility to return to the macOS Utilities screen.Keep the drive named “Macintosh HD” (or rename it if you want), and go to “Format” and choose “Mac OS Extended (Journaled)”, then click on “Erase” – ALL DATA ON THE MAC WILL BE REMOVED AND ERASED, THIS IS IRREVERSIBLE.Select “Macintosh HD” (or the name of your target Mac drive to format and clean install Sierra onto), then choose the “Erase” button.When the “macOS Utilities” screen loads, choose “Disk Utility” from the list.Continue holding OPTION key until you see a boot menu appear, choose the “Install macOS Sierra” volume from this menu.Reboot the computer, as soon as you hear the boot chime start holding the OPTION key during boot up.Attach the boot macOS Sierra install drive to the Mac.Performing a clean install will erase the Mac and you will lose any data you do not save to an external volume Be sure to back up your important files, pictures, data, or whatever else – do not skip this. We recommend having a full Time Machine backup in addition to your manual file backup which you intend to manually restore data from. Complete a backup to Time Machine before beginning.

If you don’t know what you’re doing with making manual file backups or with a clean install of macOS Sierra, don’t proceed, you will lose all data on the Mac. This is NOT the same as using Time Machine and restoring. Therefore you must backup your data manually beforehand, using a method of your choice.

Wiping over and starting over clean is the entire point of this.

Important note: a clean install will erase everything on the Mac and then install macOS Sierra, nothing else will be on the Mac.

A manual backup of your personal files, data, photos, and important information.

A Mac compatible with macOS Sierra ( see list of Sierra compatible Macs here).

If you understand the objective and are comfortable with the clean installation process, you will need the following: The vast majority of Mac users will be better served updating to macOS Sierra using the standard install and update method via the Mac App Store. Because the clean installation process involves manually backing up important files and data from a Mac (not just using Time Machine), formatting the hard drive and erasing everything in the process, using a boot installer disk to perform a clean installation of Sierra, and then manual file transfers to restore personal data, this is best reserved for advanced users.

High sierra clean install