Mode setting is a software operation that activates a display mode (screen resolution, color depth, and refresh rate) for a computer's display controller by using VESA BIOS Extensions or UEFI Graphics extensions (on more modern computers).

The display mode is set by the kernel. In user-space mode-setting (UMS), the display mode is set by a user-space process.

Kernel mode-setting is more flexible and allows displaying of an error in the case of a fatal system error in the kernel, even when using a user-space display server.

User-space mode setting would require superuser privileges for direct hardware access, so kernel-based mode setting shuns such requirement for the user-space graphics server.

On the hardware side, the GPU consists of multiple components, among which are render engine, i.e. the component of the GPU responsible for executing OpenGL/Vulkan commands, and the display engine, i.e. the component of the GPU responsible for sending a "video stream" to the screen, as opposed to the part performing rendering.

To improve performance, many GPUs come with a feature called hardware planes. Planes can make the display engine perform the composition. This is called direct scan-out and allows the compositor to avoid copying entirely. libliftoff is a library making better use of such hardware ability.

For "old" cards, support might change from distribution to distribution according to random criteria without apparent reason leaving the card unsupported.

Microsoft Windows versions that are NT-based use kernel mode setting. The kernel error display made possible by kernel mode setting is officially called "bug check", but more commonly known as the Blue Screen of Death.