A toggle is a switch that has two positions: on and off. This simple user interface component is often used to update preferences and settings in software and hardware applications. It can be found in most options menus in every piece of digital technology we use from the caps lock key on a keyboard to the pause button during a video chat with someone. Toggles are often used to provide immediate results for a small action, so it is important that the toggle labels clearly indicate the expected result. In addition, color is an essential indicator of the toggle state and designers should keep in mind societal and cultural implications when choosing colors for toggle states.

When it comes to managing toggle configuration there are a variety of approaches that range from fairly static and less dynamic (which is sometimes useful) to complex and more sophisticated. The more static approaches rely on a set of static files for management and modification which can quickly become cumbersome when you’re managing a large number of feature flags in a production environment. This is why many teams move to centralized stores which allow for dynamic in-memory re-configuration of a feature flag.

Toggle are commonly used in applications to perform multivariate or A/B testing by allowing each user of a system to be consistently sent down one codepath or another based upon their cohort. This can be used to test and implement things such as a new button label, different Call To Action wording or even a completely different UI flow for an application.