It's 2024, and the operating system wars are all but over. Windows dominates the global desktop OS market share, with macOS coming in at a distant second, bringing along a few key advantages. There's Linux, too, which is still gaining market share marginally even today. But it wasn't always this way. In the late 1990s and early 2000s, companies like Apple, Microsoft, and others were competing to create the desktop operating system of the future. And Apple was falling behind, at least until it launched its game-changing Mac OS X on this day 23 years ago.

Apple didn't find a hit with Mac OS X immediately, and it had plenty of users still on Mac OS 9 in the months and years following OS X's release on March 24, 2001. With that said, Mac OS X had a 19-year run as Apple's desktop operating system, including the years that it was rebranded to macOS 10. Although Apple moved on from macOS 10 in 2020, when it launched macOS 11 Big Sur alongside great Apple Silicon Macs, the macOS we use today is still heavily derived from Mac OS X. Put simply, OS X was one of the most influential operating systems in history, predating the MacBook entirely, surviving a platform transition, and serving as the longest-tenured Apple desktop OS ever. Here's the history of how it started and how Mac OS X evolved all the way into macOS Sonoma.

Mac OS X grew from failure

Apple bought NeXT, with the NeXTSTEP OS and Steve Jobs coming along

While we know that Mac OS X would go on to become a consistent and stable operating system, it didn't start off that way. Apple tried for years to develop a futuristic, next-generation operating system to succeed Mac OS 9. Nothing was ever released publicly, so Apple shifted plans. It instead looked to purchase an existing operating system and build off it, which is what Apple ended up doing. The company purchased NeXT, gaining the NeXTSTEP operating system and Steve Jobs in the process. Both Jobs and the NeXTSTEP operating system would be the foundation for Mac OS X.

Part of the reason that Apple's operating system goals were stagnating was due to a misguided approach. Apple was working on a next-generation OS for the Mac while also working on others, and didn't put all its focus towards any one of them. This led to miniscule updates between releases, like the tiny jump from Mac OS 8 to Mac OS 9. That changed when Jobs returned to lead Apple, when he vowed to focus on a single OS. "We are going to have a single OS strategy at Apple," Jobs told an audience at Macworld 2000. "We're not going to have a dual or a triple or quadruple OS strategy like some others. We're going to have one OS and that's very important to us."

Though Mac OS X wouldn't debut until the following year, Jobs chronicled Apple's goals for a new operating system at that Macworld conference in 2000. That included what the late Apple CEO referred to as "state-of-the-art plumbing," which included things like top-rate kernel technology and internet networking. Additionally, Jobs unsurprisingly sought "killer graphics" in Mac OS X, and wanted to make it easy for people to transition to the new operating system. Finally, Apple wanted to design Mac OS X for the internet, first and foremost. "So these were the goals for Mac OS X," Jobs said. "But to sum it up, it was [to] make the next great personal computer operating system."

Mac OS X struggled early

It was visually appealing, but lacked some basic functionality

Apple's plan for the Mac OS X release was a 12-month rollout, with new Macs shipping with Mac OS X — codenamed "Cheetah," starting the trend of big cat names — in January 2001. The company missed that target, instead ultimately shipping Mac OS X Cheetah on March 24, 2001. As was standard at the time, Mac OS X was a paid upgrade and required a software disc to be installed on supported Macs. The consensus in 2001 was that Mac OS X represented the future, but wasn't necessarily complete in the present. It was graphically excellent, although it lacked refinement and support for some basic features. On the other hand, it included a few macOS staples for the first time.

For example, Mac OS X was the first to introduce the Dock, which was a new way to launch applications. It's still around today, and has become a quintessential part of macOS. Mac OS X also brought along the Terminal, and that gave users access to the built-in Unix command-line interface. New apps included Mail, TextEdit, and Address Book. PDF support was added throughout the system, and this was part of Jobs' original goal of adding "killer graphics" to Mac OS X. Finally, Apple debuted the Aqua UI — a bubbly, water-themed graphical interface with added transparency features and other neat visuals — with Mac OS X.

But there were plenty of things missing, too. Mac OS X didn't support playing or burning CDs or DVDs at launch, and users had to wait for Mac OS X 10.1 "Puma" for that. Scheduled shutdowns and labels were nowhere to be found in Mac OS X, and there were frequent system crashes. Most of these were added or fixed by the time Mac OS X 10.2 "Jaguar" was released, but the next big Mac OS X update wouldn't come until "Leopard."

How OS X became the macOS we know today

Growing from big cats to California landmarks, and becoming great in the process

Mac OS X led to yearly iterations of Apple's software, though the naming conventions changed. It started out as Mac OS X 10.x, with a corresponding big cat codename. Then Apple ran out of big cats, and pivoted to California landmarks in 2013, starting with Mac OS X Mavericks. It switched to referring to the OS versions as macOS 10.x, but it was still solidly a rebranded Mac OS X. That finally changed in 2020, when Apple left macOS 10 (and OS X) behind in favor of macOS 11 Big Sur. After consistently making slight yearly tweaks and a few major overhauls, the macOS Sonoma we use today looks markedly different from the first version of Mac OS X. However, it's undeniably derived from Mac OS X still, even 23 years later.