macOS High Sierra (version 10.13) is the fourteenth major release of macOS, Apple Inc.’s desktop and server operating system for Macintosh computers. The successor to macOS Sierra, it was announced at WWDC 2017 on June 5, 2017.
The name “High Sierra” refers to the High Sierra region in California. As with Snow Leopard, Mountain Lion and El Capitan, the name also alludes to its status as a refinement of its predecessor, focused on performance improvements and technical updates rather than user features. Among the apps with notable changes are Photos and Safari.