How do I wipe my Mac completely
How do I completely wipe my Mac Book?
MacBook Air 13″, macOS 10.14
From the Apple menu in the corner of your screen, choose System Preferences.
From the System Preferences menu in the menu bar, choose Erase All Content and Settings.
Erase Assistant opens and asks you to sign in with your administrator credentials.
Enter the password you use to log in to your Mac, then click OK.
If you're asked to back up your Mac before resetting it, you can open Time Machine and back up to an external storage device. Or click Continue to proceed without making a new backup.
Click Continue to allow your settings, media, data, and the other listed items to be removed.
If you're asked to sign out of Apple ID, enter your Apple ID password and click Continue.
Click Erase All Content & Settings to confirm that you want to proceed.
"You are about to erase all content and settings from this Mac" popup window
Your Mac restarts and shows a black screen or progress bar. If it needs to reconnect to a Bluetooth accessory such as a keyboard or mouse, you might be asked to turn on the accessory. If the accessory doesn't connect within 30 seconds, turn the accessory off and back on. When reconnecting to a Bluetooth keyboard, you're asked to choose a language.
You might be asked to select a Wi-Fi network or attach a network cable. To select a Wi-Fi network, use the Wi-Fi menu in the upper-right corner of the screen.
After joining a network, your Mac activates. Click Restart.
After restart, a setup assistant guides you through the setup process, as if you're setting up your Mac for the first time.
For Apple Silicon: Use Disk Utility to erase a Mac with Apple silicon - Apple Support
