Mac OS X Mountain Lion (version 10.8) is the nineth major release of Mac OS X (now named macOS), Apple’s desktop and server operating system for Macintosh computers. OS X Mountain Lion brings a lot of great things from iPhone, iPad, and iPod touch to the Mac. You can send iMessages. Get your Mac in on Game Center. Receive notifications. MacOS High Sierra; macOS Sierra; OS X El Capitan; OS X Yosemite; OS X Mavericks; OS X Mountain Lion; Mac OS X v10.7 Lion; Mac OS X v10.6 Snow Leopard; Mac OS X v10.5 Leopard; Mac OS X v10.4 Tiger; Mac OS X v10.3 and earlier; Mac OS X Technologies; Classic Mac OS (OS9, OS8 & System 7) Photos for Mac; QuickTime; Safari; Front Row.
You can upgrade to macOS High Sierra from OS X Mountain Lion or later on any of the following Mac models. Your Mac also needs at least 2GB of memory and 14.3GB of available storage space.
MacBook introduced in late 2009 or later
MacBook Air introduced in late 2010 or later
MacBook Pro introduced in mid 2010 or later
Mac mini introduced in mid 2010 or later
iMac introduced in late 2009 or later
Mac Pro introduced in mid 2010 or later
To find your Mac model, memory, storage space, and macOS version, choose About This Mac from the Apple menu . If your Mac isn't compatible with macOS High Sierra, the installer will let you know.
Before installing any upgrade, it’s a good idea to back up your Mac. Time Machine makes it simple, and other backup methods are also available. Learn how to back up your Mac.
It takes time to download and install macOS, so make sure that you have a reliable Internet connection. If you're using a Mac notebook computer, plug it into AC power.
For the strongest security and latest features, find out whether you can upgrade to macOS Catalina, the latest version of the Mac operating system.
If you still need macOS High Sierra, use this App Store link: Get macOS High Sierra.
After downloading, the installer opens automatically.
Click Continue and follow the onscreen instructions. You might find it easiest to begin installation in the evening so that it can complete overnight, if needed.
If the installer asks for permission to install a helper tool, enter the administrator name and password that you use to log in to your Mac, then click Add Helper.
Please allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart, show a progress bar, or show a blank screen several times as it installs both macOS and related updates to your Mac firmware.