A toggle is a switch that has two positions, on and off. Originally, it was a pin passed transversely through an eye or a loop in a rope to fasten it, but now the word is used as a verb and to mean “switch between” or “alternate between” — for example, switching between screens as you video chat with two friends at once. Software versions of toggle switches can also be found in options menus where you choose to enable or disable functions such as sounds or animations.
Toggles are most often seen in UIs as sliders that utilize visual cues to signal state change, like movement and color. While toggles are simple they’re important to use with care as they can easily lead to confusion if the labels don’t make sense or aren’t backed by clear, direct action.
Savvy teams recognize that Feature Toggles come with a carrying cost and seek to keep them at as low a number as possible. To do this they often create a toggle removal task on the team backlog whenever a new one is introduced and they may also put “expiration dates” on their toggles which will cause automated test failures (or even the complete failure of an application!) when those toggles are still in place past their expiration date.
When a toggle configuration is managed via static files it can become cumbersome at scale, especially when the re-configuration process involves re-deploying artifacts into a testing environment. To alleviate this issue many organizations choose to implement some type of centralized toggle configuration system which can be accessed by testers, product managers and systems operators via an admin UI.