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.
OS X Yosemite (/ j oʊ ˈ s ɛ m ɪ t i / yoh-SEM-it-ee; version 10.10) is the eleventh major release of macOS, Apple Inc.' S desktop and server operating system for Macintosh computers. OS X Yosemite was announced and released to developers on June 2, 2014, at WWDC 2014 and released to public beta testers on July 24, 2014. A Guide for the creating of a patched OS X 10.10 Yosemite Installer for unsupported older Macs: Prerequisites: - get the 'Install OS X Yosemite.app' from Apple's App-Store ('OS X Yosemite Installation' in Mac 'Applications' folder) - make a BACKUP of your System if possible - get a USB-Flashdrive (8 GB or more) or use a external Hard Disk Drive. If I have created the Mac OS X Siera usb clover boot loader installer on my external usb hdd dental, install it to boot on my UEFI PC desktop computer, then says I want to use it on the 2015 MacBook Pro 13 A1502 retina to access my personal data. Safari uses these links to find the old installers in the App Store. After being downloaded from the App Store, the installer opens automatically. MacOS Catalina 10.15 can upgrade Mojave, High Sierra, Sierra, El Capitan, Yosemite or Mavericks; macOS Mojave 10.14 can upgrade High Sierra, Sierra, El Capitan, Yosemite, Mavericks or Mountain Lion.
Find out how to upgrade to macOS Big Sur, the latest version of macOS.
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 may say that it's not compatible with this device or it's 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 being downloaded from the App Store, the installer will open automatically.
Safari will download 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 will install an app named Install [Version Name]. Open that app from your Applications folder to start installing the operating system.