XCB (X protocol C-language Binding) is a library implementing the client-side of the X11 display server protocol. XCB is written in the C programming language and distributed under the MIT License. The project was started in 2001 by Bart Massey and aims to replace Xlib.Xlib/XCB provides application binary interface compatibility with both Xlib and XCB, providing an incremental porting path.