If your computer is using HFS+, be sure to choose Mac OS Extended (Journaled) from the format list

If your device uses APFS, choose APFS from the format list.Click on Erase located at the top of the window.

Most likely, it will be named Macintosh HD Keep holding it until you see the Utilities menu When your Mac restarts, immediately press and hold Command + R.Click on the Apple logo from the top left and click on Restart.If you do not have Time Machine backup of macOS Catalina, try to copy as much personal files as you can. Or if it’s just photos or videos, you can transfer them to your iPhone as well. Once you go back to Catalina, you can transfer them back. If you made documents or downloaded files while your Mac was running Big Sur developer beta, you can copy them to an external drive or save to cloud services like Google Drive. If not, you will have an internally new Mac. How to Reinstall macOS Catalina from USB Driveīefore installing macOS Big Sur beta, did you make a Time Machine backup of your Mac running macOS Catalina? If yes, you can restore all files and data from it after downgrading.How to Reinstall macOS Catalina from Internet.How to Downgrade macOS Big Sur Beta to macOS Catalina Ready To Begin?: If it is a MacBook, plug it to power as it requires significant energy, and the process is lengthy.Take a moment to see how to create a bootable macOS USB Drive. However, then you put it on a pen drive, and thus the actual installation is quick. And for the second method also require the internet to download the OS. For the first method, high-speed internet is recommended as it will download the full macOS (around 8+ GB). Two Methods: You can install macOS Catalina using the internet or a bootable macOS Catalina USB drive.Understand The Whole Process: Downgrading involves Backup (optional but recommended) → Erasing macOS Big Sur → Installing macOS Catalina → Restoring from Time Machine backup (if you have a macOS Catalina backup).Let me show you how to downgrade from macOS Big Sur beta to Catalina. But now, if you are looking to go back to macOS Catalina for any reason, it is possible. You may have installed it to check out the new features. MacOS 11 Big Sur is still in the beta version.

Revert back from mac beta os