Select Disk Utility from the macOS Utility window and click Continue. You'll be asked to select a user you know the password for, choose the one you know and enter your password. When the Utilities window pops up, the startup is then finished. Note that the way to boot into macOS Recovery mode on M1 Macs differs from Intel-based Macs. To format the startup disk, you have to boot your Mac into Mac Recovery mode first because you can't format the drive when it's in use. Step 1: Boot your Mac into macOS Recovery mode Step 3: Select the startup disk in Disk Utility.Step 1: Boot your Mac into macOS Recovery mode.The position of buttons and background color may slightly differ in different operating systems, but the overall process remains the same. Make sure you have a backup to crucial files. FAQ about how to format startup disk on MacĮrasing the Mac startup disk will cause all data stored on it permanently wiped out. Why won't my Mac let me erase the hard drive? Step 3: Select the startup disk in Disk Utility This post explains how to format the Mac startup disk with step-by-step guides.

Sometimes, you fail to reinstall macOS or want a clean reinstallation, then you will need to format the startup disk.

Reformat mac hard drive