If an error occurs while installing an update or upgrade, learn how to resolve installation issues. If you downloaded any apps from the App Store, use the App Store to get updates for those apps. If your Mac is running Yosemite (10.10), Mavericks (10.9), or Mountain Lion (10.8), it can run El Capitan. For instance, if youre upgrading from macOS Sierra or later to macOS Big Sur, this update requires 35.5 GB, but if youre upgrading from a much earlier release, youll need 44.5 GB of available storage. El Capitan is Apple’s marketing name for OS X version 10.11, the latest update to your Mac’s system software. When Software Update says that your Mac is up to date, then macOS and all of the apps it installs are up to date, including Safari, Messages, Mail, Music, Photos, FaceTime, and Calendar. The single most common reason your Mac wont update is lack of space. Software Update shows only upgrades that are compatible with your Mac. In order to access the OS X 10.11 El Capitan updater, do the following: Open Safari. Apple still offers the official OS X 10.11 El Capitan updater on the Mac App Store it is just hidden.
Then follow these steps to find and install any available software updates or upgrades.
Before you get started, it's a good idea to back up your Mac.