How to Perform a Clean Install of macOS Big Sur

Edited 3 weeks ago by ExtremeHow Editorial Team

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Performing a clean install of macOS Big Sur can be a transformative experience for your Mac. A clean installation involves erasing the hard drive and installing macOS Big Sur from scratch. This process ensures you get a fresh start with your Mac, potentially resolving software conflicts, improving performance, and removing unwanted files.

This guide will walk you through the process of performing a clean install of macOS Big Sur. Although the process may seem daunting at first, breaking it down into steps makes it manageable. Let's get started!

Preparing for a clean install

Preparation is crucial to ensure a successful clean install. Before diving into the installation process, you need to thoroughly follow several important preliminary steps. Below are the steps to adequately prepare for a clean install.

1. Back up your data

A clean install deletes everything on your Mac's hard drive, so it's important to back up all your important data. Here's how you can do it:

• Time Machine backup: Use Time Machine, macOS's built-in backup feature. Connect an external storage device to your Mac, click Apple menu > System Preferences > Time Machine, and choose "Back up now."
• Cloud backup: Consider uploading important files to cloud storage services like iCloud, Google Drive, or Dropbox.
• Manual backup: Manually copy specific files and folders to an external drive if you prefer a more hands-on approach.

Make sure your backup is complete and double-check that all important files are safely stored before proceeding.

2. Create a bootable macOS Big Sur installer

To perform a clean install, you will need a bootable USB drive with the macOS Big Sur installer. Follow these steps to create it:

• Download macOS Big Sur: Open the Mac App Store and search for macOS Big Sur. Click "Get" to download the installer.
• Create a bootable USB drive: Insert a USB flash drive (at least 16GB) into your Mac.
• Erase the USB drive: Open Disk Utility (found in Applications > Utilities). Select your USB drive, click "Erase" and format it as "Mac OS Extended (Journaled)" with the scheme "GUID Partition Map."
• Open the Terminal: Use the Terminal to create a bootable drive. Open the Terminal and enter the following command:

sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/YourUSBDriveName

Replace "YourUSBDriveName" with the actual name of your USB drive. Follow the on-screen prompts; this will take a few minutes.

3. Ensure Mac compatibility

Make sure your Mac model is compatible with macOS Big Sur. Generally, Macs from 2013 and later support Big Sur, but you should check Apple's compatibility list to confirm.

Additionally, make sure your Mac is connected to a power source during the preparation and installation process. You don’t want your Mac to shut down in the middle due to low battery!

4. Disconnect external peripherals

Disconnect any unnecessary external devices such as printers and other USB devices to prevent interference with the installation process. Keep only the essential devices such as keyboard, mouse, and drives connected to the installer.

Performing a clean install

With the preparations done, it's time to dive into the installation process. The steps below will help guide you through a clean installation of macOS Big Sur.

1. Boot from the USB installer

Restart your Mac while holding down the Option (⌥) key immediately upon startup. This action will take you to the Startup Manager, where you can select your USB drive as the boot device. Use the arrow keys to select "Install macOS Big Sur" from the list and press Enter.

2. Erase the hard drive

When the macOS Utilities window appears, follow these steps to erase your Mac's primary disk:

• Select "Disk Utility" from the list of tools and press "Continue."
• In Disk Utility, select your Macintosh HD (or equivalent) from the sidebar and click "Erase."
• Choose "APFS" for the format type, give your drive a name like "Macintosh HD", and select "GUID Partition Map" as the scheme.
• Click “Delete” to proceed.

Once the disk is erased, close the Disk Utility window to return to the macOS Utilities page.

3. Install macOS Big Sur

To install macOS Big Sur, select "Install macOS" from the Utilities window and press "Continue." Follow the onscreen instructions:

• Agree to the Software License Agreement.
• Select the disk you just erased, which should be named something like "Macintosh HD."
• Click "Install" to start the installation.

The installation will take some time, so be patient and let your Mac complete the process. Your Mac may restart several times during the installation, and it will show the progress on the screen.

Post-installation steps

Once macOS Big Sur is successfully installed, the Setup Assistant will guide you through setting up your new system.

1. Set up your Mac

Follow these steps to configure your Mac:

• Select your region.
• Select a keyboard layout.
• Connect to your Wi-Fi network and enter the password.
• Sign in to your Apple ID or create a new one.
• Set up iCloud if you want.
• Create a local account by entering your name, account name, and password.
• Choose your language settings and select "Continue."

2. Reinstall your apps

Now that you have a clean installation, you will need to reinstall the applications you use. Visit the Mac App Store to download applications associated with your Apple ID. For software purchased or downloaded from other sources, visit the respective websites to download the latest version compatible with Big Sur.

3. Restore your data

If you created a backup using Time Machine, now is the time to restore your files. Connect the backup drive and use Migration Assistant to transfer documents, apps, user accounts, and settings back to your Mac.

Alternatively, manually copy specific files and folders from your external backup drive to the appropriate locations on your new installation.

4. Update the system and applications

With your new installation, make sure everything is up-to-date. Check for macOS updates by clicking Apple Menu > About This Mac > Software Update. Apply any available updates.

To check for updates to your apps, open the Mac App Store and install any available updates.

Conclusion

Performing a clean install of macOS Big Sur can be a great way to breathe new life into your old Mac or ensure that your system is free of legacy software conflicts or a cluttered disk. By following the steps in this guide, you'll enjoy a fresh start, improved performance, and a stable system environment.

Remember that a clean install offers many benefits, but it requires careful preparation and execution. Therefore, make sure you have completely backed up your data and follow each step carefully.

By refreshing your Mac and running macOS Big Sur, you’re all set to explore the new features and updates this operating system has to offer!

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