Mac OS X 10.1 (codenamed Puma) is the second release of macOS, shipped on September 25, 2001, as a free upgrade — Apple's rapid apology for Cheetah's rough launch, distributed on CDs handed out in stores. It attacked the complaints directly: application launch and interface responsiveness improved dramatically, DVD playback and CD burning arrived, and system settings consolidated.

From January 2002, new Macs booted into Mac OS X by default — the real changing of the guard from Mac OS 9.

Major performance work; DVD Player; Finder and iTunes CD burning; Image Capture; improved AppleScript; ColorSync 4; moveable Dock. The missing pieces (native apps, gaming, speed on older hardware) remained works in progress.

Puma made Mac OS X usable and default — the release that converted the platform from demo to daily driver, and set the free-fix precedent Apple would need again. Its successor Jaguar would make the system genuinely good.