The release of Snow Leopard came nearly two years after the launch of Mac OS X Leopard, the second longest time span between successive Mac OS X releases (the time span between Tiger and Leopard was the longest). As a result of the low price, initial sales of Snow Leopard were significantly higher than that of its predecessors whose price started at US$129. On August 28, 2009, it was released worldwide, and was made available for purchase from Apple's website and retail stores at the price of US$29 for a single-user license. Snow Leopard was publicly unveiled on Jat Apple’s Worldwide Developers Conference. Mac OS X Snow Leopard (version 10.6) is the seventh major release of macOS, Apple's desktop and server operating system for Macintosh computers.