Reinstall Macos Catalina From Scratch

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macOS Catalina is slightly outdated since the release of macOS Big Sur in November of 2020. Nevertheless, many users prefer to stick with it because it's much more familiar visually. And it offers a bunch of expanded features, such as a screen extension with an iPad or the new Apple Podcasts app.
The problem is that it might not always work as intended. Glitches in macOS Catalina are commonplace: in fact, all existing operating systems like Mojave or High Sierra could freeze and crash from time to time. No software is immune.

But what do you do in this case? The surefire way to deal with jaded performance is to reinstall macOS Catalina altogether. Read through our guide below to learn how.

How To Reinstall Mac OS Catalina

The correct way to reinstall macOS Catalina is to use your Mac’s Recovery Mode: Restart your Mac and then hold down ⌘ + R to activate Recovery Mode. In the first window, select Reinstall macOS ➙ Continue. Agree to the Terms & Conditions. Access System Preferences Startup Disk and choose your Catalina installer. Restart your Mac and hold Command-R. Connect your bootable USB. In the macOS Utilities window, click Reinstall a new copy of macOS. Click Continue and agree to the terms and conditions. Select your startup drive and click Install. If you want to reinstall Big Sur and are already running Big Sur the best way to access the installer for Catalina is via the Mac App Store. For older versions of macOS and Mac OS X it's a bit. On an Intel-based Mac: Choose Apple menu Restart, then immediately press and hold Command-R. In the Recovery app window, select Disk Utility, then click Continue. In Disk Utility, select the volume you want to erase in the sidebar, then click Erase in the toolbar. Type a name for the volume in the Name field, click the Format pop-up menu.

It’s important to note that when you reinstall macOS Catalina the process simply updates the operating system and doesn’t affect any files on your hard drive or user files or even settings. That makes reinstalling principally different from performing a clean install, which erases everything.

Here are the proper steps to follow to reinstall mac OS Catalina.

1. Back up your Mac first

By default, the best thing you could do before making any significant changes to how your Mac works is to back it up. Backups are just like saves before encountering challenges in video games — represent the point you can always come back to.

There are lots of great backup solutions on the market to suit every need. If you don’t have the time to search for something specific, your Mac features a decent native option — Time Machine.

To get Time Machine started:

  1. Connect an external USB or WiFi hard drive to your Mac
  2. Go System Preferences ➙ Time Machine
  3. Click on Select Backup Disk…
  4. Press Use Disk

2. Delete junk off your Mac to speed it up

There’s nothing better than the feeling of a brand new Mac with a brand new macOS. If only the latter is new, the experience could be subpar. Trying to get the most out of macOS Catalina on your older machine might be a challenge. But don’t hurry to your local Apple Store just yet — not all is lost.

Just like the dust behind your couch or on the top of your kitchen cupboards, small bits of system files, caches, and hidden libraries tend to aggregate over the years and never get deleted, eventually slowing down everyday processes. While it’s possible to clear out some of them manually, others require specific technical knowledge and lots of time.

How to reinstall macos catalina

Luckily, there’s a professional automatic solution available — CleanMyMac X. Optimizing behind-the-curtain processes on your Mac with CleanMyMac X is no more difficult than clicking a single button:

  1. Download a free version of CleanMyMac X.
  2. Open the app and navigate to System Junk in the left-side panel.
  3. Click Scan and wait for the process to complete.
  4. When done, press Review Details.
  5. Uncheck anything you’d like to keep and click Clean.

Now your Mac is free of all the pointless log files, user caches, language files, old updates, and more. Which directly translates into improved processing power, memory usage, and response time. At last, your Mac is ready to take full advantage of macOS Catalina.

3. Reinstall macOS Catalina in Recovery Mode

With your Mac in top shape, it’s time to get that macOS Catalina download link. Surprisingly, you won’t find it in Software Update or even App Store (where it used to be in macOS High Sierra).

The correct way to reinstall macOS Catalina is to use your Mac’s Recovery Mode:

  1. Restart your Mac and then hold down ⌘ + R to activate Recovery Mode.
  2. In the first window, select Reinstall macOS ➙ Continue.
  3. Agree to the Terms & Conditions.
  4. Select the hard drive you’d like to reinstall mac OS Catalina to and click Install.

Automatically update all your software for Catalina

The reinstallation process will start shortly and roughly take 30 minutes. When complete, your Mac will start up as usual. No files should be lost, but it’s always a good idea to check CleanMyMac X’s Applications Updater to see if you can improve compatibility of the new macOS with any of your existing apps:

  1. Launch CleanMyMac X.
  2. In the left-side panel, navigate to Updater.
  3. View any available updates and their notes and click on Update.

This Updater tool in CleanMyMac X automatically searches for latest available versions of ALL your apps. One or two clicks and everything feels fresh. It even updates the macOS file itself.

Trust in your backup

Finally, in case you notice any files or apps missing, or settings misconfigured, you could open up Time Machine to restore a specific folder or the whole backup from the step one:

  1. Launch Time Machine from Applications.
  2. Simply scroll all backup versions to find the file you’re looking for.
  3. Click Restore.

If you decide to restore the whole backup, make sure to then repeat the whole process to optimize your Mac and reinstall macOS Catalina as detailed above. The good thing is that more often than not the reinstallation works wonders right from the first time.

Summary: This page is about how to reinstall macOS in macOS Recovery mode. Based on if you want to keep the original data on the startup disk, you can either choose to clean reinstall macOS or to reinstall macOS without data loss.

Reinstalling macOS gives your Mac a fresh start especially when you are frequently bothered by some issues, such as Mac not turning on, Mac hanging on the beach ball, apps frozen on your Mac, slow performance, or pink screen on Mac. Most of the time, such issue results from some system-level problems, while reinstalling macOS can easily save your life.

• How to reinstall macOS on an M1 Mac?

Reinstall Macos Catalina From Scratch

How to reinstall macOS from macOS Recovery mode?

When you need to reinstall macOS on your Mac, macOS Recovery mode makes this process easy and quick. By the way, if you want to learn more about macOS Recovery mode, you can watch this video.

To reinstall macOS in macOS Recovery mode:

Step 1: Make sure your Mac is connected to a stable Internet within all the following steps.

Step 2: Identify it's an Intel or M1 Mac, and immediately do one of the followings.

  • Press and hold Command + Option + R.This allows you to reinstall the latest version of macOS that is compatible with your Mac computer from the internet.
  • Press and hold Shift + Command + Option + R. This option allows you to reinstall the macOS that came with your Mac, or the closest version still available.
  • Press and hold Command + R. This allows you to reinstall the version of macOS stored on your built-in recovery disk, including any updates that you installed.

• How to Boot into & Use M1 Mac Recovery Mode

Step 3: Release these keys when you see an Apple logo, spinning globe, or the Utilities window.

Step 4: Enter the requested password if you are prompted to enter a firmware password or the administrator's login password.

• Recover/reset your forgotten Mac password

• Mac won't accept correct password, what to do?

Step 5: Decide if you want to clean install the system, or just reinstall macOS without losing your original data.

If you want to factory reset the Mac for selling or giveaway, or the startup disk becomes corrupted, you might want to erase the startup disk before reinstallation. This guarantees a fresh and clean installation as it wipes all your personal data on the disk.

• How to factory reset your Mac?

• How to reset your M1 Mac to factory settings?

If you only want to reinstall macOS because the original operating system is not working as you expect, you might want to keep your personal data intact. In case files are deleted or lost by accident during macOS reinstallation, you should have a backup of your data or getting files off first.

• How to get files off a MacBook that won't turn on?

Step 6: Either after erasing the startup disk or getting files off the Mac, you can then go back to macOS Utilities and choose Reinstall macOS. Check this post to find all macOS versions and know which one you are going to reinstall.

Step 7: Follow the on-screen instructions and choose a disk to reinstall the OS.

  • If the internal startup disk is not showing up, or the installer says that it can't install macOS on your computer or volume, you might need to back up files and then erase your disk.
  • If the installer asks you to choose Macintosh HD or Macintosh HD - Data when installing macOS Catalina, choose Macintosh HD.

Other ways to install macOS

Reinstall Macos Catalina From Scratch

Apart from reinstalling macOS from macOS Recovery mode, you have other options according to your situations.

How To Reinstall Macos Catalina

  1. Get released macOS versions or updates by App Store or Software Update preferences.
  2. Get macOS beta (such as macOS Monterey that might be buggy now) through Apple’s developer website.

Reinstall Macos Catalina From Scratch Full

Whatever your situation of reinstalling macOS is, you should always retrieve your data from the Mac before any further movement. After all, you can't tell if you want it back or not in the future.