There are several reasons why you may want to reinstall macOS (or even Mac OS X). Perhaps your Mac is malfunctioning and you think that a clean installation of the operating system could solve the problem.
Alternatively, you can plan to sell your Mac or hand it over to a family member (in which case you’ll need to wipe it first and factory reset your Mac).
It’s even possible to reinstall the version of macOS your Mac came with – which can allow you to downgrade to an older version of the operating system if the latest version annoys you.
Whatever your reason for reinstalling macOS, we’ll show you one of the easiest ways below.
Our method is to use a recovery partition to reinstall the latest version of macOS installed on your Mac. Since macOS is usually installed via software updates (or previously the Mac App Store), there are no physical installation discs, which is why Apple made it possible to install the operating system over the internet using Recovery HD.
An alternative option would be to create a bootable macOS installation on an external drive. If your Mac doesn’t start up in Recovery Mode, read this: Mac can’t access Recovery Mode.
We also have this article on how to clean install macOS using a boot disk.
What do you need to reinstall macOS:
Backup: If you plan on wiping your Mac as part of this process (because you think a clean array can solve the problems you’re having or because you’re selling your Mac), you may want to back up important documents first. The way you do this will depend on whether you want to recover your Mac to the same version of the Mac operating system, or if you were hoping for a clean install. For more information, read: Backing up a Mac.
Note, if you are using iCloud Drive to sync all your documents and your desktop in the cloud you may find you don’t need a backup but make sure everything is in iCloud before deleting!.
Internet connection: You must have an internet connection.
WEP / WPA: If you are using Internet Data Recovery, you must use a network with WEP or WPA security. This shouldn’t be a problem, like most home Wi-Fi networks, but if you use a proxy or PPPoE network you’ll have problems.
How to reinstall macOS using the recovery feature
Entering Recovery Mode has always been a matter of pressing and holding the Command and R buttons while booting until you hear the startup chime and see a spinning globe or the Apple logo.
However, that has changed for Macs that use Apple’s own processors, such as the M1 Macs introduced in November 2020.
If you want to go into recovery mode on the M1 Mac, you’ll need to press and hold the power button while your Mac starts up, then press and hold the button until the startup options window appears with an Options icon. Select Options and click Continue.
Follow these steps to reinstall the latest version of macOS installed on your Mac:
- Enter Recovery (by pressing Command + R on an Intel Mac or by pressing and holding the Power button on an M1 Mac)
- The macOS Utilities window will open and you will see the options Restore from Time Machine Backup, Reinstall macOS [version], Safari (or Get Online Help in older versions), and Disk Utility. The next step depends on whether you want to clean your Mac before reinstalling the operating system. If you want to clean up your disk, click Disk Utility (otherwise you can skip to step 8).
- After selecting Disk Utility, click Continue.
- Now select the volume you want to wipe. You may need to click View> Show All Disks before you can see the volume. Note that the process here is slightly different if you’re using macOS Catalina or Big Sur. If you are not using Catalina, you just need to delete the Macintosh HD volume. If you are using Catalina or later, there will be two volumes possibly named Macintosh HD and Macintosh HD-Data (or possibly Home and Home – Data). First you need to delete the data volume and then Macintosh HD. We will cover how to do that here: How to clean and format your Mac. Note that this will erase all your data, so make sure you have a backup of your important data or store it in the cloud or on an external drive.
- The next step also depends on the version of macOS you’re using. In Catalina, Mojave Big Sur and potentially High Sierra (depending on the Mac) it will be APFS. But on older Macs with older versions of macOS, you should set the format to Mac OS Extended (Journaled). You will also need to select GUID Partition Table as the scheme. (You won’t see the Scheme option if you only have a volume selected.)
- Click Erase and wait. (There are options in the security options that allow you to safely wipe the disk.)
- Now select Disk Utility> Quit Disk Utility. Or just Command + Q.
- If you are reformatting the disk, the Utilities screen reappears at this point. Alternatively, you may have jumped in from above because you don’t erase your hard drive first. Either way, you must now select Reinstall macOS from the options. If at this stage you find that recovery mode is not available, perhaps because your startup volume has been deleted, we have tips here: How to restore your Mac if recovery is not working.
- After clicking Reinstall macOS, click Continue.
- Enter your Apple ID if necessary and wait while macOS is reinstalled. Expect this to take a while.
- After running the setup wizard, finish if you intend to sell or donate the Mac so the next owner can enter their own details. Otherwise, continue setting up your Mac.
How to install an earlier version of macOS from Recovery Mode
In addition to the Command + R key combination we mentioned above, there are a few other key combinations that you can use to reinstall macOS from Recovery Mode. They let you choose whether to install the latest version of macOS that is compatible with your Mac, or the version of macOS that came with your Mac.
Note that you won’t be able to use any of these options on the M1 Mac.
You can choose from:
- Command + R Will install the latest version installed on your Mac – won’t update you to the latest version.
- Option / Alt + Command + R Will update you to the latest macOS compatible with your Mac. Note: If you are not using Sierra 10.12.4 or later this will install the version that came with your Mac; if your Mac has a T2 chip, Option / Alt + Command + R will install the latest macOS on your Mac.
- Shift + Option / Alt + Command R (if you’re using Sierra 10.12.4 or later) will install the version of macOS that came with your Mac, or the closest version that is still available.
Follow the steps in the section above to reinstall macOS through recovery. It’s only possible to run Big Sur on an M1 Mac – this could change in the future if Parallels or WMware come up with a solution to run an older macOS system in a virtual machine, but that doesn’t exist yet.
If you want to go back to an earlier version of macOS – and your Mac came with that version – you’ll be able to reinstall it using the last two options. Alternatively read: How to downgrade macOS to an earlier version.
How to connect to the Internet in macOS Recovery
You must be connected to the Internet to reinstall macOS from Recovery Mode. Follow these steps to connect to the Internet in recovery mode if your Mac did not connect automatically:
- Click the Wi-Fi menu in the upper-right corner of the screen.
- Select a Wi-Fi network.
- Enter the Wi-Fi password (if required).
Recovery Mode should now be connected to the internet and be able to download the macOS installation software.