A toggle is a switch that can be set to two possible states, on or off. It’s common to see toggles used in settings and preferences panels as well as on devices like computers and light switches.
Toggles can be triggered by a variety of different events and actions and act upon a boolean variable to change their state. The most common way is to use a button click or some other user action to trigger the toggle, but you could also use an event from a client-side script or a syslog message to cause a toggle to flip state. Then you’d have to trigger the toggle back to its previous state by some other user action.
One of the most important things about using toggles is to make sure they’re accessible for users with disabilities. This includes screen readers and other assistive technologies. A toggle is inherently inaccessible if it uses only a single color to show state, so designers often add colors to help clarify — for example green is “on” and red is “off” in many settings online. But a single toggle color can be confusing to users with visual impairments, especially for those with red/green color blindness.
Feature toggles have a wide range of uses, from experimentation to acting as circuit breakers during high latency periods in your application. They’re particularly valuable when you adopt a trunk-based development process as they allow your dev team to make changes in their branch but roll those features out only once they’ve been tested by a small group of users. They can also be used to support a product team during Beta testing and validate their new functionality with a segment of their audience before full rollout.
