El Capitan requires one of the following Macs with at least 2 GB of RAM, 8 GB of available hard drive space, and at least Mac OS X Snow Leopard (version 10.6.8): If your Mac is currently running Mountain Lion, Mavericks, or Yosemite, then it definitely meets the minimum system requirements for running El Capitan (and it might even be Sierra-capable; refer to the previous section).If El Capitan is the newest version of OS X that will run on your Mac, but you never downloaded it while it was available in the Mac App Store, you won't be able to find it in the App Store anymore.Note: Although this article was written for mac OS Sierra (10.12), much of it still applies to mac OS High Sierra (10.13) which was released in September 2017.High Sierra's system requirements are the same, except that High Sierra now requires 14.3 GB of available disk space, and a minimum of OS X Mountain Lion (10.8) to do a direct-upgrade installation.Worse, when users check the App Store for updates (or on older Macs when users run Software Update), it misleadingly tells them, "No Updates Available" or "Your software is up to date." This means that Mac users often have no idea that they're using unpatched, insecure software that could expose them to drive-by malware installations and other security problems.Lest you think that nobody would bother releasing malware to attack such old systems, in recent years malware has been found in the wild that was designed to attack multiple platforms, and occasionally this malware has contained code capable of infecting old operating systems and even Macs with Power PC G4/G5 processors (Apple's processors of choice prior to transitioning to Intel in 2006).mac OS Sierra requires one of the following Macs with at least 2 GB of RAM, 8.8 GB of available storage space, and at least OS X Lion: Those who are unsure which Mac model they own may find Every Mac and apple-history to be useful sites.
Browsers and plugins are commonly exploited as a means of infecting computers, so it's critical that these programs—along with the operating systems that run them—stay up to date.
This didn't just happen once; it has happened again and again.
While Apple boasts about the extremely high percentage of i Phone, i Pad, and i Pod touch devices that are rapidly upgraded to each major new version of i OS, such is not necessarily the case with Macs and OS X.
In other words, just because your Mac was compatible with El Capitan (OS X 10.11), Yosemite (10.10), Mavericks (10.9), or Mountain Lion (10.8) may not necessarily mean that you'll be able to upgrade to Sierra.
Some Mac models, such as 20 i Macs, are being left behind with El Capitan as their maximum OS version.