A toggle key toggles the input from a group of keys on a keyboard between two different input modes. The most common toggle key is Caps Lock, which toggles the letter keys between lowercase and uppercase mode. Some keyboards also have other toggle keys, such as Num Lock, Scroll Lock, and Insert. Below is a list of toggle keys and their functions.
- Caps Lock - capitalizes the input of all letter keys when turned on; may allow lowercase letters to be entered using the Shift key on some keyboards; does not affect the number keys.
- Num Lock - ensures numbers are input from the numeric keypad rather than arrows or other commands; typically turned on by default; may also be used to change letter keys to numbers on laptop keyboards.
- Scroll Lock - causes the arrow keys to scroll through the contents of a window when turned on; allows users to scroll using the arrow keys rather then clicking on the scroll bar at the right side or bottom of a window; not supported by most modern operating systems.
- Insert - toggles between "insert mode" and "overtype mode" when entering text; insert mode is the default mode, which inserts characters wherever the cursor is located, while overtype mode overwrites characters as the user types; also not supported by most modern operating systems.
Unlike modifer keys, toggle keys are switched on or off each time they are pressed. Therefore, toggle keys do not need to be held down when pressing other keys. Some keyboards have lights on or near the toggle keys to let the user know if they are turned on or off.
Some modern operating systems also display the status of toggle keys on the user's screen. For example, the software installed with Logitech keyboards on Macintosh computers displays a Caps Lock icon in the menu bar whenever Caps Lock is turned on.