antighosting

Antighosting is a feature of keyboards and other input devices designed to prevent ghost keypresses, erroneous signals that can occur when multiple keys are pressed at once. Ghosting is especially problematic in simple key matrices where pressing several keys can cause the device to register additional phantom keys. Antighosting seeks to ensure that the keys a user intends to press are reported accurately.

Most keyboards organize keys in a matrix of rows and columns. When a key is pressed, a switch closes a circuit, and the controller scans the matrix to detect active keys. Without isolation, signals can couple across lines and produce ghost presses. Antighosting is typically achieved by mounting diodes at each switch to prevent backflow of current, or by more advanced controller schemes that correctly interpret simultaneous signals. The result is more reliable detection of multiple keys pressed at once, which is important for gaming and fast typing.

Antighosting does not automatically guarantee that every possible combination is reported. Some keyboards advertise anti-ghosting but only support a limited number of simultaneous keys (often two or three). True N-key rollover (NKRO) means any number of keys can be pressed simultaneously and all are reported; achieving NKRO generally requires hardware and firmware designed for full simultaneous detection and may be available in specific modes or interfaces.

In common usage, antighosting improves accuracy in multitouch scenarios and reduces unintended inputs. It is a standard consideration in gaming keyboards and professional keyboards but is not a universal property of all devices.