In 1987, AT&T Corporation and Sun announced that they were collaborating on a project to merge the most popular Unix flavors on the market at that time: BSD (including many of the features then unique to SunOS), System V, and Xenix.

Although the internal designation of this release would be SunOS 5, from this point Sun began using the marketing name Solaris.

The justification for this new "overbrand" was that it encompassed not only SunOS, but also the OpenWindows desktop environment and Open Network Computing (ONC) functionality.

Matching the version numbers was not straightforward: Today, SunOS 5 is universally known as Solaris, although the SunOS name is still visible within the OS itself – in the startup banner, the output of the uname command, and man page footers, among other places.

[9] Sun then developed a novel window system called NeWS that used and extended the PostScript language and graphics model.

In 1989, Sun released OpenWindows, an OPEN LOOK-compliant X11-based environment which also supported SunView and NeWS applications.