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In some cases it may be necessary to fully reinstall the operating system on a MacBook or other Mac computer.

Please note an internet connection is required; it cannot be done offline.

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Table of Contents

Step by Step Instructions

1Power computer offIf a normal shutdown is not possible, hold the power button until the computer turns off.

Power on using the appropriate sequence.

Intel Macs (most CLICC lending Macs are Intel)

Turn on your Mac and immediately press and hold Option-Command (⌘)-R until you see an Apple logo or other image.

Apple Silicon Macs (some newer Macs)

Turn on your Mac and continue to press and hold the power button until you see the startup options window. Click the gear icon labeled Options, then click Continue.


Connect to the internet

This can be an on-campus or home connection.

In the macOS Utilities window, click on Disk Utility


Under Internal, in the left navigation, select the drive (usually named Macintosh HD)  and click the minus sign to delete it, then Delete to confirm.


Select the drive now called "APPLE SSD ..." and click Erase


Set the name to Macintosh HD, the format to APFS, and scheme to GUID Partition Map. 

Then click on Erase


Quit Disk Utility

When finished, quit Disk Utility to return to the macOS Utilities window.

Select the Reinstall macOS option.


In the following windows, agree to the terms, then click on the drive icon, then Continue.

Installation time can be around 1 hour. Once finished, the Mac will be in setup mode, and you can continue setting it up by following the prompts.

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