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How to Clean Install macOS Catalina

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This guide shows you how to clean install macOS Catalina so that you can leave behind any problems from macOS Mojave and get a fresh start. This can help you speed up an old Mac, get some drive space back and solve some issues or errors.

A clean macOS Catalina isn’t for everyone, but if your Mac is a few years old, it might be a good time to try a fresh install and clear out the junk you’ve left there over the years. Whether you upgrade or do a clean install, you still need to prepare. Here are the things that you should do before installing macOS Catalina.

Follow the steps below to perform a clean install of macOS Catalina on your Mac. Keep in mind there are some good reasons not to install macOS Catalina yet, and there are several macOS Catalina problems.

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Should I Clean Install macOS Catalina?

Not everyone needs do a clean install of macOS 10.15, but if you are suffering through macOS Mojave problems, it can help you get a fresh start and often frees up space on your SSD or hard drive.

A good rule of thumb is that if your Mac is over four years old and you haven’t done a clean install, this is a smart thing to consider if you have any issues. If your Mac is newer, you likely don’t need to do a clean install.

Read: How to Fix macOS Catalina Problems

If you do a clean install, it erases everything on your Mac. You definitely need to make sure your photos and files are backed up and that you have access to the app installers that you need. You can choose to restore from a Time Machine backup, but the point of this is to start from scratch.

How to Clean Install macOS Catalina 10.15

Download the macOS Catalina installer just like normal.

Download the macOS Catalina installer just like normal.

You need to download the macOS Catalina installer from the App Store, you need a 16GB or larger USB drive that you can format and put the update on and you may need a USB C adapter depending on your MacBook model.

Start the macOS Catalina download from the System Preferences or find it in the Mac App Store. Once it completes, do not install the update yet.

Create a macOS Catalina installer on the USB drive.

Create a macOS Catalina installer on the USB drive.

  1. Connect your USB drive to your Mac. The app will erase and format the drive.
  2. Download Disk Creator 2 and then Click on the App.
  3. Choose the USB drive from the drop-down.
  4. If not selected click on Choose Installer and pick the macOS Catalina installer.
  5. Click Create Installer.
  6. Click Erase disk.
  7. Wait for a confirmation that this is complete.

Now you have a bootable macOS Catalina installer that you can use to perform a clean install of macOS Catalina. The next step is to restart the Mac and boot into the macOS Utilities so that you can erase your drive and install macOS 10.15.

  1. Leave the USB Installer In.
  2. Turn your Mac off.
  3. Reboot your Mac while holding the option key.
  4. Click on the Install macOS Catalina option.
  5. Now click on Disk Utility.

    Erase your drive and then install macOS Catalina.

    Erase your drive and then install macOS Catalina.

  6. Click on your mac hard drive and then on Erase. Use the default options here.
  7. Name your hard drive Macintosh HD then click erase.
  8. Wait for the drive to erase.
  9. Click on Install macOS.

This will start installing macOS Catalina to your Mac. Since it is already downloaded, expect this to take about 30 minutes, which is faster than the standard macOS Catalina install time. After the installation is done, you will be able to complete the new Mac setup and get started with your Mac.

7 Reasons Not to Install macOS Catalina & 14 Reasons to Install macOS 10.15.5 Today

Install for macOS 10.15.4 Fixes and Security Updates

Install for macOS 10.15.4 Fixes and Security Updates

If you are on macOS Mojave or an older version of macOS 10.15, you should install this update to get the latest security fixes and new features that come with macOS. These include security updates that help keep your data safe and updates that patch bugs and other macOS Catalina problems.

The macOS 10.15.5 update includes the following fixes;

Battery Health Management
- Battery health management to help maximize battery lifespan for Mac notebooks
- Energy Saver preference pane now displays battery condition and recommends if the battery needs to be serviced
- Option to disable battery health management
- For more information, please visit https://support.apple.com/kb/HT211094

‌FaceTime‌ Prominence Preference
- Option to control automatic prominence on Group ‌FaceTime‌ calls so video tiles do not change size when a participant speaks

Calibration Fine-Tuning for Pro Display XDR
- Controls to fine-tune the built-in calibration of your Pro Display XDR by adjusting the white point and luminance for a precise match to your own display calibration target

This update also includes bug fixes and other improvements.
- Fixes an issue that may prevent Reminders from sending notifications for recurring reminders
- Addresses an issue that may prevent password entry on the login screen
- Fixes an issue where System Preferences would continue to show a notification badge even after installing an update
- Resolves an issue where the built-in camera may not be detected when trying to use it after using a video conferencing app
- Addresses an issue for Mac computers with the Apple T2 Security Chip where internal speakers may not appear as a sound output device in Sound preferences
- Fixes a stability issue with uploading and downloading media files from iCloud Photo Library while your Mac is asleep
- Resolves a stability issue when transferring large amounts of data to RAID volumes
- Fixes an issue where the Reduce Motion Accessibility preference did not reduce the speed of animations in a ‌FaceTime‌ group call


We will also see a list of security updates in this, which are disclosed on this security page.

The macOS 10.15.5 supplemental update includes;

  • Impact: An application may be able to execute arbitrary code with kernel privileges
  • Description: A memory consumption issue was addressed with improved memory handling.
  • CVE-2020-9859: unc0ver

If you've skipped any updates, you will also get the following fixes, which can help improve and solve many problems and bugs. The previous update included the following fixes;


  • High Dynamic Range output to HDR10-compatible third-party displays and TVs connected with DisplayPort or HDMI
  • OAuth authentication support with Outlook.com accounts for improved security
  • CalDav migration support when upgrading to iCloud reminders on a secondary device
  • Resolves an issue where text copied between apps may appear invisible when Dark Mode is active
  • Fixes an issue in Safari where a CAPTCHA tile may display incorrectly
  • Resolves an issue where Reminders may send notifications for completed reminders
  • Fixes an issue with screen brightness for the LG UltraFine 5K display after waking from sleep
  • Fixes an issue where Mac computers running macOS Catalina 10.15.4 could not participate in FaceTime calls with devices running iOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier
  • Resolves an issue where you may repeatedly receive a password prompt for an Office 365 account
  • Fixes an issue where MacBook Air (Retina, 13-inch, 2020) may hang in Setup Assistant or when disconnecting and reconnecting a 4K or 5K external display
  • Resolves an issue where a USB-C port in your Mac may become unresponsive

If you are on the edge, you may want to wait for macOS 10.15.5 reviews.

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