Mac OS X Snow Leopard (version 10.6) is the seventh release of macOS, shipped on August 28, 2009, at a pointed $29 — marketed on having "no new features." The tagline undersold a rebuild: the system went Intel-only and largely 64-bit, Grand Central Dispatch made multicore programming tractable, OpenCL opened GPUs to general computation, and the OS itself shrank by gigabytes. QuickTime X, a rewritten Finder, and Microsoft Exchange support were the visible garnish.

Its most consequential addition arrived mid-life: the Mac App Store, in update 10.6.6 (January 2011), bringing iOS-style software distribution to the desktop.

Grand Central Dispatch; OpenCL; 64-bit system apps; a smaller footprint and faster installs; QuickTime X; Exchange support; malware quarantine's quiet debut; and the Mac App Store (10.6.6). Rosetta became optional — PowerPC translation's last stand.

Snow Leopard became the reference point users invoke whenever software quality wobbles — "just give us a Snow Leopard release" remains the genre's name (and iOS 12 its mobile heir). Its concurrency frameworks underpin Apple-platform software still, and its refinement-year template proved a maintenance release could be the era's most loved.