KVM stands for "Keyboard, Video, Mouse." A KVM switch connects one keyboard, one mouse and one video display to multiple computers. This allows users to control multiple computers with only a single set of input and output devices. By sharing the inputs and the display, desktop clutter and cabling requirements can be reduced. A KVM switch may also include other switching functionality, such as for USB ports and audio.
The most common and least expensive KVM switch allows access to two computers. However, switches can be built to handle as many computers as a user requires. To switch between computers, the KVM switch may have a button or dial on the device itself. More sophisticated switches will allow the user to switch computers by using a keyboard shortcut, also known as a hot key.
A typical use for a KVM switch is in networks with dedicated servers. In everyday use, a server does not need user interaction, rendering a dedicated monitor and keyboard a needless waste of space, money, and power. In larger networks, where servers may be mounted horizontally in large racks, an entire array of servers may share one set of input and display devices via a KVM switch installed directly in the rack.
A recent development is networked KVM, which requires no physical connection between the keyboard and mouse beyond a standard Ethernet network connection. This potentially allows one user to control hundreds or even thousands of computers from one access point. Wireless routers found in homes offer something similar to this: by embedding a web server into the router, it can be accessed from virtually any connection on the network without requiring physical access to the router.
For consumers, interest in the KVM switch was spurred by the release of Apple Computer's Mac Mini. Targeted at Windows users, the Mac Mini was sold without keyboard or mouse, allowing users a relatively inexpensive way to try a Macintosh computer.