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.
Learn how to upgrade to macOS Big Sur, the latest version of macOS.
About the security content of OS X El Capitan v10.11 This document describes the security content of OS X El Capitan v10.11. For the protection of our customers, Apple does not disclose, discuss, or confirm security issues until a full investigation has occurred and any necessary patches or releases are available. OS X 10.11 El Capitan Support for Akai Pro Products. Apple released Mac OS X 10.11 on October 21, 2015. We’ve been hard at work testing compatibility with this new operating system since the final version was made available to us as developers, and while many of our products function perfectly with the new Mac OS, a few need updates.
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.