X Keyboard Extension (XKB)

In human-computer interfaces, the X keyboard extension or XKB is a part of the X Window System that extends the ability to control the keyboard over what is offered by the X Window System core protocol. The main features of this extension are:

• enhanced support for modifiers(Alt,Shift,Etc.);
• better treatment of key groups;
• extended control of keyboard indicators (LEDs) and bells;
• various new keyboard parameters (controls);
• association of actions (of a particular kind) to keys;

The extension is composed of two parts: a server extension and a client library. Modern versions of Xlib contain XKB, which is active by default. Client programs not using this extension can deactivate it before connecting with the server, or can simply work normally as the extension simulates the core protocol by default.

XKB is also used by Wayland compositors and kmscon.