The depth at which a switch will register a keystroke, usually measured in millimeters. For example, Cherry MX Brown switches have an actuation depth of 2mm. When such a key is depressed 2mm, the key will activate and electrically input the keystroke. Romer G switches have a shallower actuation depth of 1.5mm; this means they “trigger” at a shorter distance than MX Brown switches.
Other depths are defined in our additional glossary entries, as below.