Mac OS X Leopard (version 10.5) is the sixth release of macOS, shipped on October 26, 2007, after a delay Apple attributed to borrowing engineers for the iPhone. Marketed with "300+ new features," it is remembered for one above all: Time Machine, the automatic hourly backup system whose restore interface flew through a starfield of past Finder windows — backup, the chore nobody did, redesigned as something people actually used.

Leopard unified the platform's look (consistent windows, the 3D Dock, the translucent menu bar), added Spaces virtual desktops and Quick Look instant previews, shipped Boot Camp for dual-booting Windows, and became the first OS certified UNIX 03 — and the last release to boot PowerPC Macs.

Time Machine; Quick Look; Spaces; Boot Camp; Stacks in the Dock; a redesigned Finder with Cover Flow; Screen Sharing; guest accounts; Core Animation; full 64-bit application support; and UNIX certification.

Time Machine remains the standard consumer backup design two decades on. Leopard closed the PowerPC era with the platform's biggest single feature list, and its iPhone-delayed schedule marked the moment the Mac ceded Apple's center of gravity to the phone — a rebalancing its successor's quiet focus would confirm.