The word toggle means “switch or alternate.” It’s how we navigate multiple screens while video chatting with two friends at the same time or when we use Google Maps to decide where to go next on an unfamiliar route. Toggles are an important UX component that enable users to update preferences, settings, and other types of information with ease. They are especially valuable during periods of high latency when a single toggle can significantly reduce the number of page refreshes required to update content and avoid frustrating users.

Feature toggles are a key tool for modern agile development processes such as blue-green deployment. Instead of using a more traditional code branching approach for new features, which would require a complex and time-consuming testing process before they could be merged back into trunk code, toggles can hide new functionality until it’s ready to be rolled out to all customers. Toggles also serve as a safety net that allow you to roll out new features in small increments if necessary, reducing the risk of a large scale failure.

When implemented properly, toggles are easy to understand and deliver immediate results. They should be labelled clearly and designed to appear like sliders so that users can recognize their position based on relative proximity. Visual cues such as color changes and movement can help to reinforce the toggle’s state and prevent user confusion.

Toggle configuration should live in a centralized place, often an existing application DB, to make it easier for system operators, testers and product managers to modify them. Toggle configuration stored in static files can become cumbersome at scale and can impact the cycle time of your CI/CD pipeline when they must be manually changed and re-deployed into production.