Reinstall iMac: Here’s how it works


There can be many different reasons for restoring an iMac. We explain how to reset your Apple computer to the factory settings and what you should consider before and during the process.

By Sebastian Weber

The longer you keep your iMac are using, the higher the probability that the computer will run slower and slower or that unrecoverable error messages will appear. In such cases, resetting the iMac helps. What may sound daunting is easy to do.

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Make a backup before deleting

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First you should create a backup.

Image: © Apple 2021

Before we explain how to reset your iMac to factory settings, an important point to prepare: Since resetting your iMac will delete all data on the hard drive, you should create a backup.

To do this, you connect an external hard drive or a large USB stick to your iMac. Then open the system settings under “Programs” and look for the item “Time Machine”.

In this tool, click on the button that allows you to select the backup volume and specify the hard drive or the USB stick. Your iMac will then start backing up the data on it. Depending on the amount of data, this can be quick or it can take a few hours.

Disable iCloud services

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iCloud must be turned off.

Image: © Apple 2022

In addition to backing up your data, two iCloud settings are important. You can find them again in the system settings and under the item “iCloud”.

There you uncheck the “Find my Mac” box. Then click the “Log out” button.

How to format your iMac

As soon as you have completed the two points mentioned, you can start reinstalling your iMac. To do this, shut down the device and then switch it on again.

After turning on the iMac, you need to hold down the “CMD” and “R” key combination. Your iMac starts up in macOS Recovery mode, the recovery mode. This takes a little longer than a regular system start.

If you are using a Mac with an Apple processor, you do not need to use the key combination mentioned. It only works on Macs with Intel processors. If an Apple processor is installed, all you have to do is hold down the power button during startup and you’ll end up in recovery mode.

At the end of the start-up process, a window appears in which you log in, and then a selection window in which you select the disk utility. Your iMac will show you the system hard drive, usually called “Macintosh HD”. You select it and then click the “Delete” button at the top center.

Once your iMac has finished deleting the files, close Disk Utility using the red X button.

How to reset your iMac

MacOS desktop
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If you have set up your Mac again, you will find yourself on the desktop.

Image: © TURN ON 2020

You are back in the selection window from the beginning. There you select the item “Reinstall macOS”. Don’t worry, your iMac’s necessary files are backed up on another system partition that hasn’t been deleted.

Your iMac will now start installing the macOS version you had previously installed. Just follow the instructions here and install the operating system on the previously formatted system partition.

After the installation is complete, your iMac will start setting up macOS. Follow the instructions there again and choose your preferred settings.

How to restore your backup and link your iMac to iCloud

During the initial setup, macOS automatically asks if you want to restore an existing backup. In this query you choose that you want to transfer a backup.

Then connect the external hard drive or USB stick and select the connected device as the source. Your iMac then transfers all data, such as apps, back to the computer so that you can start working again immediately.

At the very end, your iMac will ask for your Apple ID and password. This is how you register the computer in iCloud again.


  • Before you set up your iMac again, you should create a backup of your data with the Time Machine tool.
  • Your iMac has a backup of the operating system stored on a hidden partition, so you can format the system drive with confidence.
  • Reinstalling your iMac is easy, but will take some time.

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