Tuesday, September 26, 2023

How to Clean Install macOS 10.15 Catalina on Mac

Apple announced the new operating system early on without precisely setting the macOS Catalina release date. We expected it for quite a while, experimenting with the Beta version. Some users weren’t confident enough to install the Beta, since bugs were expected. 

For those who waited for the official macOS Catalina release date, October 7th was the lucky day. This is a major upgrade with quite a few changes that most users love, but many criticize. 

Some are still not ready to install macOS 10.15 Catalina, since they aren’t sure if their files and apps would suffer damages. If you are one of those users, then this guide is definitely for you. We’ll guide you through a detailed process on how to clean install macOS Catalina. The steps are relatively easy even for inexperienced Mac users. There’s no need to ask a friend to help you with this; you can do it!

Tips: How to Clean Install macOS Catalina

1. Check if Your Mac Can Handle It

Before you figure out how to clean install macOS Catalina, it’s important to know if your device is compatible with the release. These are the devices that support it:

  • All iMac Pros 
  • iMacs from 2012 on
  • Mac minis from 2012 and on
  • Mac Pros from 2013 and on
  • MacBook Pros from 2012 and on
  • MacBooks from 2015 and on
  • MacBook Airs from 2012 and on

If you have an older device, you’re stuck with the Mojave. But if your computer can handle Catalina, you’ll need at least 16GB of free space on the startup disk to cover the installation. 

2. Choose the Type of Install You Want to Upgrade to 

Apple gives you two upgrade options for macOS Catalina:

  • Install macOS 10.15 Catalina while preserving all data intact. Most people have important files on their computers. Losing them would probably be a total disaster. Imagine a writer losing all their documents or a control freak losing their apps. Of course, the cloud is always there, so you can always recover things that get lost. But learning how to install macOS Catalina without losing any of your data will lead to a less stressful experience.    
  • A clean install for a fresh start. This gives you the feel of a brand new computer. During the installation process, all system junk will be gone and you’ll be left with a clean slate. This is a good option for those who don’t need any of the data on their computer. Maybe it’s full of photos and documents that you transferred on an external drive. If you don’t need anything, a clean macOS Catalina installation will make your computer faster. But even if you do this type of install, you might want to back up some of your data. This is the type of install we’ll be talking about in the continuation of this article. 

3. Clean It Up

If you’re wondering how to clean install macOS Catalina in a fast and effortless way, it’s best to do some cleaning before you start the process. If there’s tons of junk in the form of apps and files you don’t need, the installation will take more time. 

You can easily cover this step if you use a cleaning app that gets rid of file duplicates, old cache files, and all kinds of junk. 

Pay attention: you’ll get rid of 32-bit apps during this process. They don’t work on the Catalina. If your work depends on some of these apps, stay with the Mojave until app developers introduce an upgrade.

4. Back It Up

Apple offers a native app for this purpose: Time Machine. There’s a third-part option, Get Backup Pro, which creates bootable clones. 

You can use whatever backup system you prefer, just don’t ignore the necessity of it. Even if you’re sure that you don’t need anything on your current system, you might end up needing some files. 

5. Get Your macOS Catalina

Now that your Mac is clean and backed up, you’re ready for the most important stage. We recommend creating a bootable USB installer for the upgrade. 

  • Get your Catalina installer from the App Store. 
  • When the installer launches, click File > Quit. 
  • Get your USB in (you need at least 16GB of free storage space on it). It has to be properly formatted. Name it and close the Disk Utility.
  • Access the Terminal app. This is the hard part: you’ll need to enter a precise command. 

sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia –volume /Volumes/[XXX] –applicationpath /Applications/Install\ macOS\ Catalina.app

Instead of XXX, you’ll type your drive name. 

  • Return and insert the admin password. 
  • Wait patiently for the process to be finished. When it’s ready, click Done and close the Terminal.

6. Get Catalina on the Startup Drive

There. You’ve been through the hard part. From now on, it will be easy. 

  • Choose the Catalina installer, which you’ll find under Startup Disk (in System Preferences). 
  • Restart the computer, but make sure to hold Command-R. 
  • Find the option “reinstall a new copy of macOS” in the Utilities window. 
  • Continue and follow the process (you have to agree to the terms first). 
  • Choose your startup drive and proceed with the installation process. 

That’s it. After this process, your computer will feel like new. 

You Just Learned How to Clean Install macOS Catalina

We’ve been waiting for the macOS Catalina release date for too long. Now that the operating system is finally here, many people hesitate to install it. Don’t worry; a clean install is pretty easy to do. That command above might overwhelm you, but it’s really not that difficult to enter it when you know what it is. 

There’s another issue that worries Mac users: what if they can’t free up enough space on their startup drive? There’s a solution for that: it’s possible to install the operating system on a non-startup drive. The process is simple:

  • If the drive is not new, then erase it. It has to be clean. 
  • Download the macOS installer from the App Store and click Quit as soon as it launches. 
  • Launch the installer from the Applications folder and choose the drive that you want it on. Proceed with the steps as the installation process guides you. 

When you’re using an Apple product, there’s usually a solution for any problem you face. That’s why you love your Mac so much. Now make it even better with the new operating system. It will be love at first sight!  

Andy Debolt
Andy is a graduate of the University of Minnesota with a Bachelors Degree in Journalism. When he isn't writing Andy enjoys water sports and spending time on the golf course.


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