Mac OS X Server 1.0, released on March 16, 1999, is the first operating system released into the retail market by Apple Computer based on NeXT technology. It was the final release of the product code named Rhapsody, which was an interim combination of the OpenStep system (Mach OS and OpenStep API) and Mac OS 8. Although Mac OS X Server 1.0's graphical "look and feel" was a variation of the Platinum theme from Mac OS 8, its infrastructure is based on the OPENSTEP (and thus, NeXTSTEP) operating system instead of the classic Mac OS. The resulting product gave users a preview of the operating system which was to become Mac OS X. Mac OS X Server was never officially known simply as Mac OS X, and was ultimately obsolesced by Mac OS X v10.0 in 2001.
Server 1.0 contains a mix of features from the classic Mac OS, NeXTSTEP and Mac OS X. Like classic Mac OS, it has a single menu bar across the top of the screen, but file management is performed in Workspace Manager from NeXTSTEP instead of the classic Mac OS Finder. The user interface still uses the Display PostScript-based window server from NeXTSTEP, instead of the Quartz-based WindowServer which would appear a year later in Mac OS X Public Beta. Unlike any version of Classic Mac OS, windows with unsaved content display a black dot in the window close button like NeXTSTEP did. The Dock and the Aqua appearance were not included; these were added later in Mac OS X.
"Carbon", essentially a sub-set of "classic" Mac OS API calls, was also absent. This meant that the only native applications for OS X Server 1.0 were written for the "Yellow Box" API, which went on to become known as "Cocoa". Furthermore, Apple's own FireWire was not supported.
Server 1.0 also includes the first version of a NetBoot server, which allows computers to boot from a disk image over a local network. This was particularly useful in a school or other public-machine setting, as it allowed the machines to be booted from a single OS copy stored on Server 1.0. This made it difficult for users to damage the OS by installing software – as soon as they signed out, the machine would re-boot with a fresh OS from the NetBoot server.
To run classic Mac OS applications, Mac OS X Server 1.0 includes the "Blue Box" which essentially ran a copy of Mac OS 8.5.1 in a separate process as an emulation layer. Blue Box would eventually be renamed as the "Classic Environment" in Mac OS X, featuring the latest version of Mac OS 9.