To get the latest features and maintain the security, stability, compatibility, and performance of your Mac, it's important to keep your software up to date. Apple recommends that you always use the latest macOS that is compatible with your Mac.
Similar to Mavericks, (OS X 10.9), Mountain Lion (OS X 10.8) and Lion (OS X 10.7), Apple’s upgrade to Yosemite is a pretty major one, but will be really simple to install. But before you do that, you should perform a few tasks to ensure that you’re Mac is ready to go.
Learn how to upgrade to macOS Big Sur, the latest version of macOS.
Reinstalling Yosemite on a computer already running it. Reinstalling while keeping files, applications, and settings; Reinstalling while erasing everything on your computer; Upgrading from previous versions to OS X 10.10 (Yosemite) OS X 10.10 (Yosemite) is no longer available for purchase from the Mac App Store. Bottom line: Should you upgrade to OS X Yosemite? By Christopher Breen. Mavericks and, perhaps, Mountain Lion, probably weren’t either. Apple’s been building this bridge for a long time. The Apple Company introduces the new operating system that they will begin to use the Mac this year: the Yosemite. The version will replace the current operating system OS X Maverick. The OS will come with some important changes, especially, in the form of icon images. Furthermore, Apple wants their users to upgrade to this version.
The version of macOS that came with your Mac is the earliest version it can use. For example, if your Mac came with macOS Big Sur, it will not accept installation of macOS Catalina or earlier.
If a macOS can't be used on your Mac, the App Store or installer will let you know. For example, it might say that it's not compatible with this device or is too old to be opened on this version of macOS. To confirm compatibility before downloading, check the minimum hardware requirements:
Safari uses these links to find the old installers in the App Store. After downloading from the App Store, the installer opens automatically.
Safari downloads the following older installers as a disk image named InstallOS.dmg or InstallMacOSX.dmg. Open the disk image, then open the .pkg installer inside the disk image. It installs an app named Install [Version Name]. Open that app from your Applications folder to begin installing the operating system.