Complete Guide for How to Reinstall macOS on MacBook/iMac

Home > HowTos > Troubleshooting Tips Updated by William on May 11, 2024 | Approved by Jennifer Allen

Various reasons may warrant that you reinstall Mac OS on your computer. For instance, if you want to sell or give your Mac to another person, you may want to reinstall macOS. It is also a great idea to reinstall macOS if you are experiencing software issues on your Mac. Other reasons that may require that you go through this process include:

Whatever reasons you have for deciding to reinstall macOS Big Sur, the good news is that it is easy to complete the process. You do not need a professional to get the job done. So, how do you reinstall macOS on your MacBook/iMac?

Quick Navigation
Part 1: How to Reinstall macOS without Losing Data
Part 2: How to Erase and Reinstall macOS
Part 3: How to Reinstall macOS using Recovery Mode
Part 4: How to Reinstall the Mac Original macOS
Part 5: How to Reinstall Mac to the latest macOS
Part 6: Frequently Asked Questions for Reinstalling macOS

Part 1: How to Reinstall macOS without Losing Data

Everyone stores tons of data on their Mac and the major worry that comes with reinstalling macOS is the possibility of losing data. However, you do not have to worry about this because you can reinstall macOS without losing data if you follow the appropriate method.

Ordinarily, macOS reinstallation should not cause lost data. That is because the reinstallation process does not delete or alter your saved data and programs in any way. However, just in case something goes wrong, it is best to back up your data before you reinstall macOS without losing data.

How to Back up Mac before Reinstalling macOS

It is crucial to back up data before reinstalling macOS. You can use various methods to complete this process, including the following.

Method #1: Use Time Machine

  1. Connect an external storage drive to your Mac computer.
  2. Navigate to Finder and then Application and launch Time Machine.
  3. Select "Set Up Time Machine".
  4. lick on the "Select Backup Disk" button to select the external drive to back up your data.
  5. Check the "Back Up Automatically" box and wait for the process to complete.

Method #2: Use Hard Drive

  1. Connect a hard drive to your Mac computer and click to open Finder to locate the drive under Devices.
  2. Create a new folder and then copy and paste files you want to save from your Mac to the new folder and eject the hard drive.

Method #3: Use iCloud

  1. Navigate to Finder and then System Preference. Click on "iCloud" to open the main interface
  2. Click on "Options" and click on the box in front of "Desktop & Documents Folders". Next, click "Done".

When you choose either way to complete the backup of important data, you can start to Reinstall macOS without losing data.

Part 2: How to Erase and Reinstall macOS

The first thing to understand is that once you erase the data on your Mac, it will be impossible to recover the deleted files. If you think you may still require files on your hard drive, it is best to back up your data through Time Machine or sync your files to iCloud.

If you are ready to erase and reinstall, you can use the Erase Assistant tool. To erase and reinstall macOS, follow the steps below:

  1. Click to open "System Preferences" and click "Erase All Content and Settings" from the menu bar.
  2. Enter the admin password in "Erase Assistant" and review the items you want to remove. Note that apart from erasing all media, data, apps, and settings for all accounts and folders on the drive, it will also delete Touch ID fingerprints, sign you out of iCloud, unpair Bluetooth devices, remove Apple Wallet items, and disable location services.
  3. Before the final erasure, you can make a final creation of a Time Machine backup. To do this, click on "Open Time Machine" to create the backup.
  4. To complete the erasing process, provide your password to sign out your Apple ID. This will return the Mac PC to the factory settings and reinstall a new macOS on it.

Part 3: How to Reinstall macOS using Recovery Mode

Recovery Mode is the easiest way to reinstall macOS because it cleans the codes of the running OS and rewrites it with a new version. The first step is to back up your data. Next, you need to identify the model of your Mac. Whether it is an Apple silicon Mac or an Intel-based Mac will determine how you launch the Recovery Mode.

For Intel-based Mac:

  1. Shut down the system completely. Next, turn it on as you hold down "Command + R" simultaneously.
  2. Release the keys when you see an Apple logo and your system booting into the macOS Utility window.

For M1/M1 Max/M1 Prom Mac:

  1. Shut down the Mac and press down on the Touch ID button to power it on.
  2. Press down the Touch ID button immediately again until you see Loading startup options.
  3. Click "Options" and then "Continue" to boot your computer in macOS Recovery.
  4. While booting up to Recovery Mode, you may need to provide the admin password for authentication to continue with the OS reinstallation.

    When you have entered the functioning recovery partition, you can continue to format the startup drive and select to reinstall Mac OS from macOS Recovery Mode. To reinstall macOS, follow the steps below:

  5. Select the "Reinstall macOS" option and click on "Continue".
  6. Select the specific destination to install the new macOS copy and choose the startup disk.
  7. Do not shut down your computer or put it to sleep until the "install macOS Catalina" process finishes.

Part 4: How to Reinstall the Mac Original macOS

You must have an Intel-based Mac to install the original version of macOS. Here are the simple steps to complete the process:

  1. Press on "Shift + Option + CMD + R" to boot your Mac into macOS Recovery. Consider backing up your data before you continue with the process.
  2. If you want to erase Mac and reinstall OS, CLICK "Disk Utility" to erase the Macintosh HD Data partition of the startup drive.
  3. If you do not want to erase data from your Mac, click on "Reinstall macOS" and follow the on-screen prompts to download and reinstall the new OS. Wait for your Mac to install the closest available macOS version to what it came with when you bought it.

Part 5: How to Reinstall Mac to the latest macOS

Just like with the Mac Original macOS, reinstalling Mac to the latest macOS is only available for Intel-based Mac systems. To reinstall the latest compatible version of your macOS, follow the steps below:

  1. Click to open "System Preferences".
  2. Click on "Software Updates".
  3. Hold down "Option + CMD + R" to boot your system into macOS Recovery
  4. Click "Reinstall macOS now" and wait for the download to begin. After the download, it will install the latest version of macOS on your device.

Part 6: Frequently Asked Questions for Reinstalling macOS

  1. macOS Big Surcannot be installed on Macintosh HD. What are the possible reasons and how to solve them?
  2. Answer: Different reasons may be responsible for why macOS Big Surcannot be installed on Macintosh HD. It may be that your Mac does not support Big Sur, the update cannot be downloaded, you do not have enough disk space, or there is a conflict in your system preventing the installation process.

    Whatever is the reason, you can resolve it. Check to see if your Mac is compatible with it. If it is not compatible, you will not be able to run Big Sur. Mac devices that are compatible with Big Sur are Mac Pro and iMac Pro, MacBook Pro and MacBook Air 2013 or later, Mac 2015 or later, and iMac and Mac mini 2014 or later.

  3. How do I completely reinstall my Mac?
  4. Answer: You can use macOS Recovery to completely reinstall your Mac computer. The macOS Recovery keeps your user settings and files safe during the reinstallation process. Make sure that your computer is connected to the internet while reinstalling macOS.

  5. Does reinstalling OS delete everything on Mac?
  6. Answer: No, reinstalling macOS does not delete all data saved on your Mac. When you reinstall macOS on top of the latest installation, it reinstalls from the Recovery partition with the same Command + R reboot.

    Although OS reinstallation does not delete everything on your Mac, it is recommended that you back up your computer before reinstalling. It is best to boot your Mac in Recovery mode to reinstall macOS in a non-destructive way. This will ensure that your documents, user files, settings, and other data are intact.

  7. Can you reinstall macOS without disk?
  8. Answer: Yes, you can. To reinstall macOS without disk, you should ensure that your Mac is turned on all through the process. Your computer should also be connected to the internet. It is recommended that you make a Time Machine backup of your Mac computer before continuing the process.

    To reinstall macOS without disk, turn on your Mac while you old down the "CMD + R" keys and select "Disk Utility". Next, click "Continue". Select the "Startup Disk" and then click the "Erase Tab". Select "Mac OS Extended" and name your disk. Next, click "Erase". Next, click on "Reinstall Mac OS" and follow the onscreen prompts to complete the process.

  9. How to reinstall macOS from USB?
  10. To reinstall macOS from USB, the flash drive must be at least 12GB in size. You should note that this process will erase the USB flash. Therefore, make sure you remove all files on the drive before you continue.

    To complete the process, open your app folder and check to see if you have the Install files for the specific version of macOS that you need. If you have the installer, attach the USB flash to your Mac and open "Disk Utility".

    Choose the volume in the sidebar and click "Erase" Make sure that the volume shows "Untitled" in the name field and do not change it. Open the terminal and then cut and paste the right createinstallmedia text in the Terminal.

    Note that the code depends on the macOS version you have. Next, enter the admin password. Next, enter "Y" and click "Return". This will wipe the flash drive and convert it into a bootable installer. Next, shut down your computer and press down Option/Alt and the Power button. Select the startup device list window and click "Return".

    Select Disk Utility and then the drive under Internal. Click "Erase" and name the drive. Click "Erase" and then "Done". Select Disk Utility and then Quit Disk Utility. Next, select "Install macOS" and then click "Continue". Follow the prompts to complete the process.

  11. Can I Recover Lost Files after Reinstall macOS?
  12. Answer: Yes, if you backed up important data before resetting, you can restore them using the backup file. If not, you don't have to worry, you can still use Mac data recovery software to retrieve lost files.

This post looks at the complete guide for how to reinstall macOS on MacBook/iMac using different methods. It also provides the solution for Mac Big Sur cannot be installed on Macintosh HD.

With the comprehensive details given in this post, you should be able to reinstall macOS on your Mac and resolve any issue you may encounter in the process. As mentioned, make sure to backup your data before you carry out the process.