• APFS BootROM Support: If you have a machine that supports High Sierra natively, you MUST ensure you have the latest version of the system's BootROM installed. If you have NOT previously installed High Sierra, you can download and install this package (if running OS X 10.10 Yosemite or later) to install the latest BootROM version (you MUST reboot after installing the package to apply the.
• 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.

Easy way to Clean Install mac OS Catalina

After that, you click on Power on this Virtual machine. At the first step, the VM will install macOS Catalina necessary files. It will take up to 20 minutes to complete the installation process. Installing macOS Catalina. After the installation is completed click on “Restart”.

macOS Catalina is Apple’s shiny new operating system for the Mac and it’s got a ton of great features and improvements. You’re probably keen to get started and install it straight away. Before you do, consider whether you want to install it over the top of your current OS, or as a completely clean install of macOS Catalina. The benefits of the latter are that it will be like a completely new Mac, with all your settings wiped out, and junk files gone. It should make your Mac run faster. The rest of this article will explain how to clean install macOS Catalina.

Before the clean installation of macOS 10.15 Catalina it’s recommended that you first delete junk and dusty files from the current macOS. There are many free and paid tools to clean junk but the quickest option is to run CleanMyMac X. You can expect to free up tens of gigabytes of space, including old apps, and their leftovers.

Here’s how it works.

1. Download and install CleanMyMac — try a free edition of the app here
2. Choose the System Junk tool.
3. Press Scan.
4. When it’s finished either press Remove to get rid of all the files it recommends, or choose Review to look through what it’s found and decide for yourself what to delete and what to keep.

Backup your Mac

I can’t stress how important this is. You must backup your Mac before you do anything else. You’re going to be erasing your startup drive completely, so you need a complete backup of everything. You can use Time Machine, another backup app, or a cloning tool. Just make sure you have a complete, preferably bootable, copy of your current installation.

You should also make notes of settings for apps you use regularly – screen grabbing them is a good way to do that. And you should make sure you have a copy of any licence codes that you’ll need when you reinstall applications. You can use Apple’s Notes app to make notes, as long as you sync them with iCloud.

Create a bootable installer of macOS Catalina

If you’re reading this after Catalina ships, you can download it from the Mac App Store and then choose Quit when the installation starts. If you’re clean installing the beta (and, by the way, that’s not something I would recommend. It’s much better to create a dual boot system when you run the beta.

1. Grab a USB stick with a capacity of at least 16GB, or an external hard drive or USB.
2. Go to Applications>Utilities and launch Disk Utility.
3. Launch Disk Utilities and Erase the Drive or USB stick, formatting it as Mac OS Extended (Journaled) or APFS and selecting GUID partition map if a selection is available.
4. The easiest method for creating a bootable installer is to use DiskMaker X. However, if you’re comfortable using Terminal, you can do it like this:
   1. Launch Terminal from Applications>Utilities
   2. Type: sudo /Applications/Install macOS Catalina Beta.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install macOS Catalina Beta.app where ‘Untitled’ is the name of your USB stick or external hard drive
   3. Press Return and wait for the word Done to appear in Terminal.

Once you see ‘Done’ in Terminal you can quit it. Your USB stick or external hard drive is now a bootable Catalina installer, so keep it safe. Now, it’s time to clean install macOS Catalina.

How to Clean install macOS Catalina

Now you've made a backup and created a bootable installer, it's time to actually install the new macOS. Follow these easy steps to clean install macOS Catalina on your Mac.

1. Plug your USB stick or external hard drive into your Mac, if it’s not plugged in already.
2. Restart your Mac while holding down the Option key.
3. When you see the options for booting appear on screen, choose the installer disk you just created.
4. When you see the macOS Utilities screen appear, choose Disk Utility
5. When Disk Utility launches, choose the Eras tab then select your startup volume (probably called Macintosh HD).
6. Give your startup disk a name, then choose a format. If you have a recent Mac with an SSD startup disk, select APFS. If you have an older Mac with a mechanical hard drive or Fusion Drive, choose whichever one you want to use.
7. Choose Erase.
8. When Disk Utility has finished erasing the disk, quit it to return to the macOS Utilities screen.
9. Choose Install macOS.
10. Press Continue and choose the drive you just erased and re-formatted as the destination.
11. MacOS Catalina will start to install.
12. When it’s finished, your Mac will restart and it will look like a brand new Mac. Go through the set-up process to set up a user account, add your wifi network, choose a language, and log in to iCloud.

Once you’ve set up your Mac, you can eject the installer disk and remove it. Remember to keep it safe. You can now restore files you backed up earlier from Time Machine or whichever backup tool you used. Remember to restore files and folders individually, don’t, for example, restore your entire user directory otherwise you’ll copy back all the junk files you just got rid of. Reinstall applications and go through them adding license details where necessary. Check that everything works as you expect it to and use the screen shots you made earlier to configure settings.

There are lots of good reasons why you might want to clean install macOS Catalina, but the most important one is that it should make your Mac feel like new and keep it running smoothly. For ultimate Mac refresh you can also download CleanMyMac X and play with its cleanup tools. Getting rid of old junk feels great.

Attempting to download macOS Catalina from the Mac App Store you may find that a small version of the “Install macOS Catalina.app” file downloads to the “Applications” folder, rather than the complete 8.1 GB installer file.

The tiny (just tens of megabytes) incomplete installer requires an internet connection during usage to download the rest of the Catalina update files. Additionally, it does not allow to create a macOS Catalina USB installer drive for use on multiple computers.

In this tutorial, I’ll show you how to download the complete “Install macOS Catalina.app” file from Apple server using the “macOS Catalina Patcher” app instead of via the Mac App Store.

A similar mini-installer issue occurred previously with some users getting a tiny incomplete macOS High Sierra installer and macOS Mojave installer too and I covered a similar workaround here and here to download the complete installer file from Apple server.

About the app

In this workaround, we’re going to use the macOS Catalina Patcher app from the dosdude1.com. This app is intended for those with unsupported Macs and Hackintosh users, but any Mac user can use the app to be able to download the complete macOS Catalina installer file from Apple server. For our purposes in this particular walkthrough, we will use the app only to download the complete installer file.

Note! This method relies on a third party app from an unverified third party source. If you are not comfortable with using unvetted and unverified software, do not follow this process.

Let’s begin

Install Catalina From Big Sur

Downloading the complete “Install macOS Catalina.app” file from Apple server using the “macOS Catalina Patcher” app is a really easy process. Now, step by step guide.

Go to the official website of the “macOS Catalina Patcher” app here and download the app.

The download link is labeled as “Download Latest Version” on that page.

Launch the “macOS Catalina Patcher” app.

Note! By default, macOS preventing apps from unidentified developers or sources from being launched. So you most likely will get an alert message that says: “macOS Catalina Patcher.app can’t be opened because it is from an unidentified developer”. To allow just one specific app to run do the following:

1. Hold down the Control key and click the app icon. From the contextual menu choose Open.
2. A popup will appear asking you to confirm this action. Click the Open button.

Click the “Continue” button, and then select “Download a Copy”.

Confirm that you want to download the “Install macOS Catalina.app” app to start the download to your hard drive.

Close the “macOS Catalina Patcher” app when the download is complete and locate the “Install macOS Catalina.app” file you downloaded.

Note! The download will be completed when you are prompted to choose an installation method. See the screenshot below.

Conclusion

That’s it, you’re done. Now you have the complete “Install macOS Catalina.app” file downloaded. So simple isn’t it?

Install Catalina On Older Mac

You can confirm that you have the complete “Install macOS Catalina.app” file by getting info on the file. For this simply select the file and click the Spacebar key (or right-click on the file and choose “Get Info”). The complete installer should be around 8.1 GB rather than the tiny (just tens of megabytes) incomplete installer that requires additional downloads.

Note! Remember, the “Install macOS Catalina.app” file deletes itself automatically after macOS Catalina has successfully installed. Therefore, you may want to make a backup by having previously copied it to external storage.

Let me know in the comments section if you know another way to download the complete “Install macOS Catalina.app” file rather than the tiny incomplete installer.

Install Catalina Mac

I hope this article has helped you learn how to downloaded the complete “Install macOS Catalina.app” file from Apple server. If this article has helped you then please leave a comment

Thanks for reading!

Arthur is a designer and full stack software engineer. He is the founder of Space X-Chimp and the blog My Cyber Universe. His personal website can be found at arthurgareginyan.com.