XRandR

XRandR, short for the X Resize, Rotate and Reflect extension, is an extension to the X Window System that enables dynamic configuration of display properties. It allows the X server and its clients to discover available display outputs, resolutions, and refresh rates, and to change the geometry, orientation, and reflection of screens at runtime without restarting the server.

The extension introduces a model consisting of screen resources, outputs (monitors), CRTCs (display controllers), and available modes. It supports operations such as enabling and disabling outputs, selecting a mode for each output, rotating the display, and applying reflection or mirroring. RandR also provides hotplug support, so when monitors are connected or disconnected, the configuration can be reconfigured automatically or by the user. The framework is designed to support multiple outputs and flexible arrangements, allowing complex multi-monitor setups with independent or synchronized configurations.

XRandR is implemented as a core part of the X.Org Server and is supported by major graphics drivers for Intel, AMD, NVIDIA, and other hardware. It is commonly accessed by user-facing tools such as the xrandr command-line utility and various graphical display configuration tools integrated into desktop environments. In modern stacks that use Wayland, RandR operates within XWayland or is superseded by native Wayland display protocols, but it remains a foundational feature for traditional X11 environments and compatibility layers.