The XCB util module provides a number of libraries which sit on top of libxcb, the core X protocol library, and some of the extension libraries. These experimental libraries provide convenience functions and interfaces which make the raw X protocol more usable. Some of the libraries also provide client-side code which is not strictly part of the X protocol but which has traditionally been provided by Xlib.

The XCB util module provides the following libraries:

- aux: Convenient access to connection setup and some core requests.

- atom: Standard core X atom constants and atom caching.

- event: Some utilities that have little to do with events any more.