A toggle is a piece of software or hardware that allows a user to update preferences, settings, and content. It’s found in nearly every aspect of computing that offers an options or preferences menu. When a toggle is turned on, its behavior changes; when it is turned off, the object reverts to its default state. For example, the Caps Lock and Num Lock buttons on a keyboard are toggles for those specific functions; when pressed, they turn the function on, and when pressed again, they switch the function back to off.

Feature-toggling is a mechanism used to perform multivariate testing or A/B testing in web applications and services such as Google Chrome Canary. By establishing different codepaths to an application and tracking user data, it is possible to make informed optimizations of user experience (UX) and conversion rate.

Toggles are also found in hardware such as light switches and automated door systems; they act the same way by allowing a user to switch an object’s function on or off. A toggle script consists of a trigger script that establishes an on/off relationship with one or more togglable objects; during run-time, the trigger script listens for key input and when a key that exists in the list of togglable objects is pressed, the toggle script executes and alters the toggling object(s) accordingly (for a schematic depiction, see Fig. 4, left).

Multiple triggers may impact a single togglable object simultaneously; the toggle script executing with a particular trigger passes a control number to the target toggle(s) which will be modified in accordance to that value (for a visual depiction, see Fig. 5, right). A togglable object, in turn, can possess more than two defined states; a toggle script can also be triggered by multiple triggers in order to switch the toggling object(s) between different states.

While toggles are powerful tools that can dramatically improve UX, they should be used sparingly and with caution. When they are used, their purpose should be clearly defined and they should be easily understood by users. It is important to provide clear labeling and use standard UX visuals. For example, a toggle should not be used to hide a navigation bar or other critical interface elements. In addition, toggles should always be clear about what will be turned on or off and they should deliver immediate results. Toggles should never be used to replace real-time config options such as a config file or an external service.