This section describes the peculiarities of using Emacs built with the GNUstep libraries on GNU/Linux or other operating systems, or on macOS with native window system support. On macOS, Emacs can be built either without window system support, with X11, or with the Cocoa interface; this section only applies to the Cocoa build. This does not support versions before Mac OS X 10.6.
For various historical and technical reasons, Emacs uses the term ‘Nextstep’ internally, instead of “Cocoa” or “macOS”; for instance, most of the commands and variables described in this section begin with ‘ns-’, which is short for ‘Nextstep’. NeXTstep was an application interface released by NeXT Inc during the 1980s, of which Cocoa is a direct descendant. Apart from Cocoa, there is another NeXTstep-style system: GNUstep, which is free software. As of this writing, Emacs GNUstep support is alpha status (see GNUstep Support), but we hope to improve it in the future.