This is the volume with all your data in it. Just below this, you will see Macintosh HD – Data. This is named Macintosh HD by default unless you renamed it. Next, you will see a window where the sidebar on the left in Disk Utility will show the name of your startup disk. Select ‘Disk Utility’ and click the ‘Continue’ button at the bottom right. You can use macOS Recovery and use its utilities to recover from certain software issues, reinstall macOS and also to repair or erase the disk. It is part of the built-in recovery system of your Mac. The combination of the keys will open macOS utilities in macOS recovery. You can release the keys when you see the Apple logo on the screen. Once the Mac has shut down, press and hold the Command + R keys and then press the Power key on your Mac to boot into the macOS Recovery menu. For doing this you need to shut down your Mac by selecting ‘Shut Down’ from the Apple Menu at the top left corner of your Mac home screen.

Once we have the backup ready we can proceed to erase the disk. This is in case if any files are missing during formatting or installation, the Mac can automatically download them from Apple servers. We would also recommend that you connect your Mac to the Internet via WiFi or Lan cable before beginning the process. We strongly recommend that you take a backup of your data on Mac using Time Machine so that we can restore your data after formatting it. In this article, we will show you how to erase the hard drive on your Mac and reinstall macOS before you hand it over to someone else or fully restore the Mac to its factory state if it is having some issues. You might also want to erase data on the drive and reinstall macOS if your Mac has run into some software issues and is not working as expected and First Aid in disk utility is unable to fix the problem. You wouldn’t want all your data which includes your files, pictures, videos, and apps, etc to be there on the Mac when you sell it. If you are planning to give away or sell your Mac then the first thing you should do is to erase the data on it. Complete guide to truly clean your Mac machine!

Your startup disk is full mac