Mac OS X 10.0 'Cheetah' Ships to the Public
Released March 24, 2001 at $129, Mac OS X 10.0 brought Apple's NeXT-derived, Unix-based operating system to consumers for the first time.
Mac OS X 10.0, internally codenamed “Cheetah,” was released to the public on March 24, 2001, at a retail price of $129. It was the first consumer release of the operating system Apple had been building since acquiring NeXT four years earlier.
What shipped
Mac OS X 10.0 introduced the Aqua interface — a significant visual departure from the classic Mac OS’s interface conventions — running on top of a genuine Unix-based core (Darwin) inherited from NeXTSTEP. It brought real preemptive multitasking and protected memory to the Mac platform for the first time, addressing exactly the reliability limitations that had motivated the NeXT acquisition in the first place.
Because so much existing Mac software wasn’t yet updated for the new architecture, Mac OS X 10.0 shipped with a Classic compatibility environment, letting older Mac OS 9 applications run inside a compatibility layer while native “Carbon” and “Cocoa” applications were developed for the new system.
A rough but foundational start
Mac OS X 10.0 is broadly remembered as an important but rough initial release — performance was a common complaint, and application support was still thin at launch. Apple iterated quickly: 10.1 shipped later the same year with substantial performance and compatibility improvements, and the operating system’s Unix foundation and Aqua interface direction remained the trajectory Apple continued building on for every subsequent macOS release.
Why this release mattered beyond its own version number
10.0’s significance isn’t really about what it got right on day one — it’s that it was the first tangible, shipping proof that the NeXT acquisition strategy actually worked: a genuinely modern, Unix-based operating system, running on Mac hardware, that regular consumers could buy. Every macOS internals topic covered elsewhere on this blog — launchd, APFS, code signing, SIP — exists downstream of this specific release being the moment that foundation first reached the public.
Sources: Mac OS X 10.0 — Wikipedia, Apple launched its revolutionary OS X 20 years ago — AppleInsider