This post is about display servers and windowing systems compatible with Linux, that provide graphical user interfaces.
List of Linux Display Servers
X Windows System
X Window System is an specification for a window system for Unix-like systems. X11 is the latest version of this specification as of 2025.
Programmers at Massachusetts Institute of Technology (MIT) started developing X in 1984.
X11 is distributed under an MIT license since 1986.
The most popular free and open implementation of X Window System is X.Org Server, backed by the X.org Foundation.
xfree86 is a X Window System implementation originally implemented by IBM that is now dormant, mainly replaced by X.Org Server.
Wayland
Wayland is a protocol that specifies the communication between a display server and its clients.
A display server using the Wayland protocol is called Wayland compositor.
There are Wayland compositors like Mir (originally developed by Canonical), Mutter (part of the GNOME shell) or Sway.
Wayland became the default display server with the release of Ubuntu 21.04 in April 2021.