In the menu bar, clickErase All Content and prefs.
This will remove your personal data and any apps you installed without removing macOS.
Connect your MacBook to the internet.
Apple
Otherwise, you won’t be able to wipe the hard disk.
Go tomacOS Utilitiesscreen and selectDisk Utility.
Select your hard disk.
choose the disk rather than any volumes nested within the disk.
Enter anamefor the disk, such asMac HDor whatever else you find appropriate.
If you’re using macOS High Sierra or later, go to the Format drop-down menu andchoose APFS.
If you’re using macOS Sierra or earlier, chooseMac OS Extended (Journaled).
In the Scheme drop-down menu, chooseGUID Partition Map(if shown).
ClickEraseto begin the wiping process.
In the upper-left corner of the MacBook Pro screen, click theAppleicon.
Choose your external drive.
ClickEncrypt backupsand then selectUse Disk.
If it isn’t in the ON position, selectONafter clickingUse Disk.
When you do, the MacBook Pro begins creating a backup.
click theAppleicon and selectSystem Preferences>iCloud>Sign Out.
For Messages: PressCommand+Space Bar, typeMessages, and pressEnter.
At the top of the Mac’s screen, selectMessagesand then selectPreferences>iMessage>Sign Out.
On the macOS Utilities screen, clickReinstall macOS.
When the installation is complete, you’ll see the setup/Welcome screen.
