macOS Big Sur was the release that changed Apple’s Mac operating system’s major version number from 10 to 11.
Announced at WWDC on June 22, 2020, Big Sur became available to the public on November 12, 2020. It followed macOS Catalina 10.15, ending the long sequence of releases branded as Mac OS X or OS X 10.x. Apple had used version 10 since Mac OS X 10.0 Cheetah in 2001, even as the system received many substantial upgrades.
The version-number change accompanied a major visual redesign, including refreshed icons, translucent interface elements, and Control Center. Big Sur was also the first macOS release to support Apple silicon Macs, while retaining compatibility with Intel-based models. Apple’s Rosetta 2 technology helped many Intel applications run on the new architecture.
A common mix-up is confusing Big Sur with later names: Monterey is macOS 12, Ventura is macOS 13, and Catalina is macOS 10.15. Big Sur’s name refers to California’s rugged Central Coast region.