As was mentioned earlier today during Apple’s special event, Mac OS X 10.10 Yosemite is now available as a free upgrade for users running OS X 10.8 Mountain Lion and 10.9 Mavericks. To get the update, you can head to the Mac App Store or, alternatively, simply click this direct link.
OS X Yosemite comes with a redesigned look and feel to bring the OS aesthetic more in line with iOS, as well as several groundbreaking new features like iCloud Drive, Continuity, revamped Spotlight, widgets for Notification Center, and more. Notably, however, some of these features require newer hardware.
Mac OS X Yosemite has been in testing for many months now, since its introduction at WWDC 2014 in June. Each beta has ironed out more and more bugs, leading up to the most recent introduction of a few GM versions.