The model and year of your Mac will determine which macOS you can upgrade to, You can learn more about how to upgrade to macOS Catalina here: How to upgrade to macOS Catalina - Apple Support You can download OS X El Capitan 10.11.6 here: Download OS X El Capitan You can download macOS High Sierra 10.13.6 here: Get macOS High Sierra You can download macOS Catalina 10.15.3 here: Get macOS Catalina Be careful downloading update files from other sources. The Mac App Store is the best, and usually only, place to download macOS updates. Download the update from the App Store.If your Mac isn't supported still, you could still upgrade to OS X El Capitan. If your Mac doesn't support macOS Catalina, it might be supported by macOS High Sierra, which requires a Mac introduced in 2009 or 2010. The latest version of macOS, macOS Catalina, is supported on any Mac introduced in 2012 or newer. Check what version of OS X or macOS your Mac supports.You'll need at least 8 to 22 GB of free storage space to upgrade to a newer version of OS X or macOS. Make sure that you have enough storage available for a software update.