XQuartz
Updated: 02/27/2019 by Computer Hope
XQuartz is a free, open-source display server for macOS. It enables a macOS user to run GUI (graphical user interface) programs designed for the X Window System.
XQuartz was developed in collaboration between Apple, Inc. and the X.Org Foundation in the early 2000s, at the beginning of the OS X era of Apple operating systems. The first non-beta version was released in 2003 for macOS X 10.3 Panther. The most recent version was released in October 2016.