macOS Big Sur (version 11) is the seventeenth release of macOS, shipped on November 12, 2020 — the release that ended seventeen years of "10.x" numbering and booted the first Apple-silicon Macs. The M1 transition it carried was the platform's biggest hardware shift since Intel, executed with Rosetta 2's near-invisible translation and Universal 2 binaries — and, as a bonus, iPhone and iPad apps running natively on the desktop.

The redesign matched the moment: the deepest visual overhaul since Aqua, with floating translucent panels, iOS-style icons, Control Center and a rebuilt Notification Center, and refreshed system sounds.

Apple-silicon support with Rosetta 2; the full-depth redesign; Control Center on Mac; Safari's biggest update (start page, tab previews, translation); Messages parity with iOS (pinned chats, effects); signed system volume; and iOS/iPadOS apps on M1.

Big Sur is the Apple-silicon era's founding release — the smooth M1 launch it enabled reset the industry's laptop expectations overnight — and its version-number jump signaled that the "Mac OS X" epoch had ended. Its design remains the platform's current visual base, refined through Tahoe's Liquid Glass.