OS X Mountain Lion (version 10.8) is the ninth major release of macOS, Apple Inc.' S desktop and server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012 for purchase and download through Apple's Mac App Store, as part of a switch to releasing OS X versions online and every year, rather than every two years or so. May 01, 2016 Can i have dual osx on My MacBook i currently have el capitan but i need mountain lion to get My mackie audio device to work again how do i do this? More Less MacBook Pro (13-inch Mid 2012), OS X El Capitan (10.11.3). Mountain Lion OS X 10.8 is a great operating system from Apple. It’s the last version of OS X that supports some video conversion applications and it runs very fast so downgrading from El Capitan to Mountain Lion is the best option for me. Important Information before downgrading from El Capitan to Mountain Lion.
macOS Big Sur elevates the most advanced desktop operating system in the world to a new level of power and beauty. Experience Mac to the fullest with a refined new design. Enjoy the biggest Safari update ever. Discover new features for Maps and Messages. And get even more transparency around your privacy.
Check compatibility
macOS Big Sur is compatible with the following computers. If your Mac isn't compatible, you might be able to install an old version of macOS instead.
MacBook introduced in 2015 or later
MacBook Air introduced in 2013 or later
MacBook Pro introduced in late 2013 or later
Mac mini introduced in 2014 or later
iMac introduced in 2014 or later
iMac Pro
Mac Pro introduced in 2013 or later
View the complete list of compatible computers.
If upgrading from macOS Sierra or later, your Mac needs 35.5GB of available storage to upgrade. If upgrading from an earlier release, your Mac needs up to 44.5GB of available storage. To upgrade from OS X Mountain Lion, first upgrade to OS X El Capitan, then upgrade to macOS Big Sur.
Download macOS Big Sur
If you're using macOS Mojave or later, get macOS Big Sur via Software Update: Choose Apple menu > System Preferences, then click Software Update.
Or use this link to open the macOS Big Sur page on the App Store: Get macOS Big Sur. Then click the Get button or iCloud download icon.
Install macOS Big Sur
After downloading, the installer opens automatically. Click Continue and follow the onscreen instructions.
Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, it might restart and show a progress bar or blank screen several times. You might find it easiest to begin installation in the evening so that it can complete overnight, if needed.
Stay up to date
Mac Os X El Capitan
After installing macOS Big Sur, you will be notified when updates to macOS Big Sur are available. To check for updates, choose Apple menu > System Preferences, then click Software Update.