Clean install macOS Big Sur on a Mac. This guide can be followed if you are upgrading from macOS Catalina, or you are finding that macOS Big Sur is giving you tons of issues such as slowdowns, app. 'macOS Big Sur' could not be verified.: I have tried twice to update from Catalina 10.15.7 to Big Sur and every time I get this message. Why does the update not work?.I have tried to install as per your feedback in safe mode, but it goes back to the fault message.” ———-Reinstall it All Anew. Installing MacOS Catalina from Big Sur You’re now watching this thread and will receive emails when there’s activity. Click again to stop watching or visit your profile/homepage to manage your watched threads. After months of waiting, macOS Big Sur was released in November 2020. No matter how great macOS Big Sur is, you can experience performance issues as you update your Mac. The good thing is you can downgrade to the previous macOS version. There are two ways to revert from Big Sur to Catalina. The first one involves restoring a Time Machine backup.
After months of waiting, macOS Big Sur was released in November 2020. No matter how great macOS Big Sur is, you can experience performance issues as you update your Mac. The good thing is you can downgrade to the previous macOS version.
There are two ways to revert from Big Sur to Catalina. The first one involves restoring a Time Machine backup. The second, which is a bit lengthy, explains how to downgrade to Catalina using a bootable installer. Whichever way you choose, we'll provide step-by-step instructions to help you downgrade.
Open this article on your phone to make sure you do everything step-by-step.
How to downgrade from macOS Big Sur using Time Machine
If you’ve backed up your Mac with Time Machine before upgrading to Big Sur, downgrading to Catalina will be easy. Here’s how to downgrade from macOS Big Sur to Catalina using Time Machine.
1. Back up your data
First, back up everything. Your Mac probably contains your personal data and documents that you don’t want to lose. So, to keep those alive after the downgrade, you need to back up your data.
You can use Google Drive, iCloud Drive, or any other cloud you prefer. After the backup is done, you can move on to the next step.
Before you begin reverting your Mac to macOS Catalina, it’s worth trying fixing performance issues on macOS Big Sur. Maybe you won’t need to downgrade at all.
CleanMyMac X can help identify and solve performance problems on your Mac. It’s a dedicated Mac cleaner that clears old junk and runs optimization tasks. It’s notarized by Apple, which means it’s safe for your Mac. Get CleanMyMac X for free to run a quick performance scan.2. Erase your Mac’s hard drive
The first step is plugging your Mac into power (the downgrade process may take a while, and you don’t want your Mac to power off unexpectedly).
You’ll need to erase your Mac’s drive. This will remove everything from your Mac, but you can restore your data later from a Time Machine backup.
- Restart your Mac (Apple menu > Restart).
- Hold Command-R when your Mac’s rebooting. The Utilities menu should appear.
- Choose Disk Utility.
- Click Continue and select Startup Disk (usually located at the top of the list ).
- Press Erase.
- Select the APFS file format.
- Choose GUID Partition Map and confirm.
Wait for the process to complete. Only after every piece of data is removed, can you clean install macOS Catalina.
3. Use Time Machine to restore your backup
You can now restore all your files and data and bring your Mac back to the condition it was in before you installed macOS Big Sur.
How To Downgrade Big Sur To Catalina
If your Time Machine backup is stored on the external drive, plug it in your Mac.
So, to restore your Time Machine Catalina backup:
- Restart your computer and hold Command-R when it reboots.
- Select the Restore From Time Machine Backup option on the Utilities window.
- Press Continue.
- Choose your Time Machine backup disk.
- Select the backup you want to restore from. Choose the most recent backup that occurred before you installed macOS Big Sur.
- Then, select a destination disk, where the contents of your backup will be stored.
- Click Restore and press Continue.
The process may take some time. Your Mac will restart running macOS Catalina.
How to downgrade from macOS Big Sur using a bootable installer
If you didn’t back up your Mac with the Time Machine, it’s too bad. But, you can still downgrade to the previous OS version. Just follow the instructions.
1. Back up your files and data
Backing up your data is important. It prevents you from losing all the files and data that have existed on your Mac's drive for a while. So, don’t forget to back up your Mac before you start downgrading to Catalina.
2. Create a bootable installer
A bootable installer will help you safely roll back to Catalina. Here’s how to create a bootable installer:
- You can go to the App Store and search for Catalina, then download it. Quit the installer, if it tries to install the OS.
- If your Mac already runs macOS Big Sur, download the macOS Catalina here.
- Get an external hard drive that has at least 12 GB of available storage and plug it in your Mac.
- Launch the Disk Utility app and erase your hard drive selecting Mac OS Extended format.
Now, it’s time to transfer your Catalina installer to your hard drive:
- Open Terminal (Applications > Utilities).
- Paste this command and press Enter:
sudo /Applications/Install macOS Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
The downloaded file, which is your bootable Catalina installer, should be in your Applications folder. MyVolume is the name of the hard drive; if your hard drive or flash drive has a different name, replace MyVolume with the name of your hard drive.
- If prompted, enter your administrator password and press Enter again. Terminal won’t show anything when you type your password.
- Follow the instructions that appear in the Terminal.
- When Terminal says “done”, your hard drive should have the same name as the installer you downloaded (for example, Install macOS Catalina).
Quit Terminal and eject the hard drive.
Install macOS Catalina
Now, you can roll back from macOS Big Sur using the bootable installer.
- Plug your hard drive (which is now your bootable installer) into your Mac.
- Open System Preferences > Startup Disk. Choose your bootable installer as a startup disk and press Restart.
- Your Mac should start up to macOS Recovery.
- Make sure your Mac has an internet connection to download firmware updates (you can use the Wi-Fi menu in the menu bar).
- In the Utilities window, select Install macOS.
- Click Continue and follow the on-screen instructions.
Your Mac will then start installing macOS Catalina and will restart when it’s done.
Mac runs slowly after the update?
If your Mac is slow after the update, but you don’t want to perform this lengthy process and revert to the previous OS, you could try a quick solution. CleanMyMac X has a helpful Maintenance feature that could fix all possible problems on your Mac.
- Open CleanMyMac X.
- Go to the Maintenance module.
- Press View All 9 Tasks.
- Check the boxes next to the maintenance tasks you want to run.
- Press Run.
Wait till CleanMyMac X runs the set of fixes to speed up your Mac.
Reverting to the previous macOS may seem like a terrifying task. But if you open this article on your phone or another device and follow the instructions, it will be much easier and faster. Don’t forget to clear your Mac before the backup – you will save a lot of free space and remove old clutter that slows down your machine.
I’ll admit it: I’ve gotten a little used to working at smaller companies, where there’s no monitoring of company computers, and it’s the Wild West as far as what you can install on them.
That’s no longer the case for me. I now work at Auth0, a company with a headcount that’s quickly approaching 800, with unicorn status and Series F funding, and it’s in the security industry. Naturally, there’s a full-fledged security team that monitors company-issued computers.
In my excitement to take the new version of macOS — Big Sur — out for a spin, I’d forgotten that the Security team hasn’t yet approved it for use. They very quickly (and I should add, nicely) contacted me and let me know that I needed to reinstall macOS Catalina as soon as possible.
There are other reasons why you might need to go back to Catalina after installing Big Sur:
- It’s still very new, and very new versions of operating systems always have some set of issues, whose effects can run the gamut from mildly annoying to catastrophic. If you can’t afford to lose time dealing with these issues, you should wait for the updates.
- There are reports that the current version can “brick” MacBook Pros from the 2013 / 2014 era. This isn’t a problem if you’re keeping your old 2013 / 2014 machine around as a backup, but more serious if you’re still using it as your main computer (and yes, a 2013 / 2014 Mac is still a perfectly good machine, even for development work).
- If you’re a DJ or music producer, Big Sur currently has compatibility problems with some of the hardware and software. If you want to keep DJing, producing, or mixing on your Mac, stay on Catalina for a little bit.
For the benefit of any who need to downgrade, here’s a step-by-step guide to reinstalling Catalina after you’ve installed Big Sur. You’ll need a USB key and the better part of an afternoon.
Step 1: The preliminaries
1a: Start downloading the Catalina installer from the App store
The first thing you’ll need is the macOS Catalina installer.
It’ll take up around 9 gigabytes of space on your hard drive, and the App Store will put in your Applications folder.
Reinstall Macos Catalina From Big Sur Windows 10
Once it’s completely downloaded from the App Store, the installer will start automatically. When this happens, close the installer. You’ll make use of it later.
The installer will take some time to download. Apple’s servers will be busier than usual, as many users are downloading Big Sur and other upgrades.
1b: Back up your files!
In the process of reinstalling Catalina, you’ll need to completely erase your Mac’s hard drive. If you have any files that you can’t live without, this is the time to back them up.
I didn’t have to worry about this, since:
- All my work product is either code (which lives on GitHub) or content (which lives on GitHub or Google Docs), and
- I’ve been at Auth0 less than a month, and between onboarding and offsites, there just hasn’t been that much of a chance for me to accumulate that many files on my hard drive!
1c: Get a nice fast USB key that stores at least 16 GB
The process will involve booting your Mac from a USB key containing the macOS Catalina installer, so you’ll need a key with enough space. An 8 GB USB key won’t be big enough. Because digital storage is all about powers of 2, the next size up will be 16 GB.
I strongly recommend that you use a USB 3 key, especially one with read speeds of 300 megabits/second or better, such as the Samsung Fit Plus. Doing so will greatly speed up the process. Don’t use a USB key that you got as conference swag — it may have the space, but more often than not, they tend to be slow, because they’re cheap.
If the USB key contains files that you want to keep, back them up. You’re going to erase the key in the next step.
Step 2: Make a bootable USB key containing the macOS Catalina installer
2a: Format the USB key
Plug the USB key into your Mac, then launch Disk Utility.
Select the USB key in Disk Utility’s left column, then click the Erase button:
You’ll be presented with this dialog box:
Enter MyVolume into the Name field, and for Format, select Mac OS Extended (Journaled). Click the Erase button. This will format the USB key with the volume name of MyVolume.
2b: Install the macOS Catalina installer onto the USB key
In Step 1a, you downloaded the macOS Catalina installer and closed it after it started automatically. In this step, you’ll transfer it to your freshly-formatted USB key.
Open a terminal window and paste the following command into it:
(The command above assumes that you gave the USB key the volume name MyVolume.)
Once you’ve provided sudo with your password, you’ll be asked if you want to erase the USB key. Entering Y in response will start the process of making the USB key a bootable drive and copying the macOS Catalina installer onto it:
The Erasing disk process will be relatively quick, but the Copying to disk process may take a while. This is where using a nice, fast USB 3 key will pay off.
Be patient and let it get to 100%, and wait for the Install media now available message to appear and the command line prompt to return.
2c: If your Mac is from 2018 or later, set it up to boot from external media
Check the year of your Mac’s manufacture by selecting About This Mac under the Apple menu:
- If your Mac year is 2017 or earlier, you don’t need to follow the rest of this step. Proceed to Step 3.
- If your Mac’s year is 2018 or later, you’ll need to change its security settings to allow it to boot from an external drive.
Here’s how you change the security settings:
- Restart your Mac and hold down the ⌘ and R keys when you see the Apple logo. This puts the computer into recovery mode, which provides many setup options.
- In the menu bar, select Utilities, and then select Startup Security Utility from the list that appears.
- The Startup Security Utility window will appear:
- Under the Secure Boot section, select Medium Security. This will allow you to install Catalina without having to connect to a network.
- Under the External Boot section, select Allow booting from external media. This will allow you to install Catalina from a USB key or disk drive.
Step 3: Install macOS Catalina
Restart your Mac, and hold down the Option key while it restarts. Your Mac will present you with a choice of startup disks.
Choose the USB key. Your Mac will boot up and you’ll be presented with the macOS Catalina installer screen:
Go ahead and install Catalina.
Once Catalina is installed, you can proceed reinstalling your other software.
Once that’s complete:
- If your Mac’s year is 2017 or earlier, you’re done installing Catalina. You can now go about reinstalling your software and restoring your backed up files.
- If your Mac’s year is 2018 or later, you’ll need to restore its original security settings. The process is described in Step 4, below.
Step 4: If your Mac is from 2018 or later, restore the original security settings
If your Mac is from 2018 or later, follow these steps to restore the original security settings once Catalina has been installed:
- Restart your Mac and hold down the ⌘ and R keys when you see the Apple logo. This puts the computer into recovery mode, which provides many setup options.
- In the menu bar, select Utilities, and then select Startup Security Utility from the list that appears.
- The Startup Security Utility window will appear:
- Under the Secure Boot section, select Full Security.
- Under the External Boot section, select Disallow booting from external media.