On Sept. 13, 2000, Apple released Mac OS X Public Beta, the first public release of OS X to include the Dock. It was also the first to feature the unprecedented eye candy that was the Aqua interface. It marked the beginning of a new era for Mac, and one we’re still living in 20 years later.

A Lifeline for Apple

By the late ’90s, Apple’s classic Mac OS felt antiquated. It didn’t support protected memory, pre-emptive multitasking, or user-level access control. It was also prone to frustrating system crashes.

Its interface design was, arguably, also falling behind Windows. Apple knew Mac OS needed a fundamental redesign from the ground up. However, software compatibility issues pushed Apple to keep extending the same basic system architecture it had used since 1984.

The quest to replace classic Mac OS was a long and messy process. It involved several internal projects and a search for an acquisition target that might bring new technology to the company. This led Apple to purchase Steve Jobs’ NeXT in 1997 with the intent of making its NeXTSTEP operating system the basis for a new, modern replacement for Mac OS.

With Steve Jobs’ NeXT crew in charge, Apple began juggling the needs of legacy Mac owners, while attempting to make NeXTSTEP palatable to a mass audience. The result was Mac OS X.

Unlike Classic Mac OS (but like NeXTSTEP), Mac OS X was based on a Unix-like BSD core called Darwin. This made it incredibly stable and built the foundation for the Mac to become the amazing developer platform it became. Modern versions of macOS are still based on the Darwin core.

After some early beta versions of OS X were released to developers in early 2000, Apple decided to make the new OS available on CD-ROM through its website for $29.95. This allowed Mac owners to put the new software through its paces.

Customers who purchased the CD also received a $30 discount on a future purchase of Mac OS X 10.0 (the Public Beta version expired on May 14, 2001). This gave people enough time to sample the new OS and provide valuable feedback to Apple.

An Aqua Revolution

In 1999, Apple released an early version of OS X based on prototypes called Rhapsody. It was basically NeXTSTEP re-skinned with Apple’s classic Mac OS “Platinum” theme.

While the underlying new technology was there, Rhapsody’s boring look didn’t excite many people. It also didn’t inspire developers, who grumbled about having to rewrite their Mac software for the new platform.

Apple knew it needed something special to attract more attention. The company secretly started working on a flashy new interface called Aqua. It included built-in support for large icons, and shadows and transparency. The colorful buttons and interface elements also had a fresh translucent look.

The Aqua interface was a huge surprise when Steve Jobs first announced it at the Macworld Conference and Expo in January 2000 (see the video below). During his demo, Jobs delighted in showing off graphical features we now take for granted, like drop shadows beneath windows, icon magnification, and high-resolution icons.

Aqua’s appearance has changed over the years, and Apple no longer refers to it by name. Still, it’s the basis of the modern macOS Catalina interface.

The Mac OS X Dock also debuted at that January 2000 demo. It provided a flexible, capable way of launching and managing apps. It also finally allowed Mac OS to catch up with the functionality of the Windows task bar.

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Notable Similarities and Differences

The similarities between the 20-year-old Mac OS X Public Beta and macOS Catalina are pretty amazing. They both have the Dock, high-resolution icons, three window control buttons (red, yellow, and green), global PDF support, and run on Darwin.

There’s a cast of familiar built-in applications, as well: Preview, Mail.app, TextEdit, Address Book, Stickies, QuickTime, Calculator, and an early version of Chess.

Mac OS X Public Beta also had some notable differences from Mac OS X and later macOS releases. One of the most obvious was the Apple logo was in the center of the menu bar, rather than the upper left.

While Mac OS X Public Beta’s pinstripe theme and translucent candy buttons persisted until Mac OS X 10.2, they were eventually replaced by a brushed metal look with Mac OS X 10.3 Panther.

OS X Public Beta also lacked some functional convenience features, like Exposé, Widgets, Notifications, and Launchpad. It also didn’t include an App Store—that didn’t arrive until 2011 as a download on OS X 10.6 Snow Leopard.

A few notable Apps were also missing. Instead of Safari (which debuted in 2003), the Public Beta shipped with a version of Internet Explorer that had a special Aqua theme.

OS X Public Beta also included a cutting-edge search app called Sherlock that was later replaced by Spotlight.

There’s also no sign of iTunes or Apple Music, but just a bare-bones Music Player that could play CDs or MP3s. Even missing these, though, its wide suite of included applications and utilities makes Mac OS X Public Beta still feel relatively modern.

A Continuing Legacy

Avie Tevanian, the former chief software technology officer at Apple and a Mac OS X developer, once said Apple designed OS X with a 20-30 year life span in mind.

In 2000, 30 years must have seemed like an unthinkably long time for a software architecture to remain viable. Yet, here we are at nearly the end of 2020, and OS X (now “macOS”) continues to do the heavy lifting for Macs. And it will likely continue to do so for at least another decade, across many architectural shifts.