The simplest and most reliable way to redownload macOS Big Sur directly from macOS Big Sur is by using the command line. Assuming you’re currently on a Mac running Big Sur (11.0 or later) here is all you need to do: Open the Terminal application (hit command+Spacebar and type Terminal, then hit return, or launch it directly from Utilities). Now you are ready to downgrade from macOS Big Sur to Catalina. As we mentioned above, you can restore the earlier macOS from the backup or reinstall it using a bootable installer. If you use Time Machine, follow these steps to reinstall macOS Catalina: Connect the external drive with a backup to your Mac. Restart your Mac in Recovery Mode.
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.
Reinstall macOS Catalina on Your Mac. Restore Time Machine Backup (Optional) Step 1. Back up your Mac (Very Important) If you want to downgrade from Big Sur to Catalina without losing data, it is important to save and backup your data on the macOS Big Sur, so you do not lose any important files.
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.
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.
Reinstall Macos Catalina From Big Sur Windows 10
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.
Reinstall Macos Catalina From Big Sur Free
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.
If you've upgrade to macOS Big Sur but decided to stick with macOS Catalina because of annoying bugs still not resolved in Big Sur, it is easy to roll back or downgrade from Big Sur to Catalina by following the guidelines shared in upcoming section. Before the downgrade starts, please make sure you have backed up important data on your Mac. This can be done with Time Machine, the stock app for file backup on macOS.
Notice: No matter which method you are going to pick up for downgrading Big Sur to Catalina, please backup your data on Mac first. You can sync them to cloud drive or an external backup drive.
Potential Bugs for macOS Big Sur
Operating system is a enormous software project that needs hundreds of developers to work together. So it is inevitable to avoid bugs and errors. This also applies to OS Big Sur, the latest version of macOS. Some of the major issues you may have on Big Sur and may be the main reason to put you back to old versions of macOS like Catalina or Mojave.
- Some apps can not run properly like Dropbox, Google Drive.
- App craches after launch.
- Media import may not work in iMovie and Final Cut Pro.
- Can not sign in iCloud sign-in.
- Some keyboard shortcuts not working on non-English languages.
- Weather widget display incorrect location.
Method 1: Directly Downgrade from Big Sur to Catalina
macOS Catalina is the official app you can use to install Catalina on current Mac on the air. This is the direct way to downgrade from Big Sur to Catalina. You don't need to make additional settings as the whole process is quite straightforward and safe.
Step 1: Search 'Catalina' in App Store on your Mac running with Big Sur.
Step 2: Click 'Get' button at the top to download macOS Catalina install app. When it starts, you will see a progress bar in Launchpad and you have to wait for minutes to fully download the app because the app is pretty big.
Step 3: The installer will be opened automatically when the download is completed. Just follow the screen prompt to install macOS Catalina on your Mac. The process will overwrite Big Sur installation in a safe way.
This method still works till the day we wrote the post. However, macOS Catalina will be no longer available after a period of time according to Apple convention. Please don't worry. You can still apply the following two methods to downgrade macOS from a new version to old one.
Method 2: Downgrade from Big Sur to Catalina by Deleting Big Sur Installtion
If your Mac is originally shipped with macOS Catalina, you can then downgrade from Big Sur to Catalina by removing the current Big Sur installation in Recovery Mode. After that, Mac will start downloading and installing Catalina from Internet (Apple Server).
Step 1: Make sure your power adapter is connected because this could take a while. Now, restart the Mac but hold down the Command+R key combination during boot. Next, choose the Disk Utility app when you see the macOS Utilities window on your screen. The purpose of this is to be able to erase Big Sur installation and re-format it for macOS Catalina.
Step 2: Hit the Continue button and choose the option for Startup Disk. Click the Erase option, then choose APFS as your file system and GUID as your partition scheme.
Step 3: Quite Disk Utility app and back to macOS Utilities. At this time, please choose Reinstall macOS and hit Continue button. After that, follow the screen instructions to install macOS on your Mac.
Your Mac must be connected to Internet if you chose to downgrade from Big Sur to Catalina in this way. And this may take hours to complete if the download speed was too slow.
Method 3: Downgrade from Big Sur to Catalina by Reinstalling Catalina
Another possible solution is to install macOS Catalina over Big Sur partition via a bootable USB drive. If the above two methods do not work, then you can use this trick to downgrade from Big Sur to Catalina. However, you should create a macOS Catalina USB installer first. This can be done with the help of UUByte DMG Editor.
Step 1: Get macOS Catalina DMG file from here.
Step 2: Download and install UUByte DMG Editor onto a Windows PC or Mac.
Step 3: Plug in a USB drive and open UUByte DMG Editor app; then click 'Burn' section. You will be lead to a new window immediately, where you can import Catalina dmg file and select USB drive.
Step 4: When the setting part is done, click 'Burn' button to create a bootable Catalina USB drive. You need to wait about 10 minutes in this step.
Step 5: Turn off your Mac with the bootable USB drive still plugged in. Wait 2-3 minutes and reboot your Mac with Power + Option key. This will open up macOS Startup Manager, where you can choose a temporary booting device this time. Now, click the USB drive name and starts to install macOS Catalina on your Mac.
Summary of the Process
To help you get a clear picture of how to downgrade from macOS Big Sur to macOS Catalina, the steps are summarized below:
- Erase startup disk and reformat it.
- Get macOS Catalina Install App.
- Create bootable macOS Installer USB.
- Boot your Mac from this USB drive.
- Start installing macOS Catalina in Recovery mode.
If you want to do this once Big Sur is officially launched, you may not be able to get the installer file from the Mac App Store. In that case, you will need to download a DMG disk image file from a third-party source in order to complete the downgrade. Our recommendation is to get the installer file now while it's available as an official download. That way, even if you decide to downgrade later, it will be much easier.