Toggle is a word that refers to both a simple user interface element and a verb meaning “to alternate between two positions, as when you toggle screens during a video chat with two friends at once.” In software development the term can also be applied to configuration options that are either On or Off. Toggles can make it easy for users to update their preferences or settings, and they’re often used in place of more complex interface elements like dropdown menus.

Toggles are also useful for implementing feature experimentation and A/B testing. In these scenarios we can configure a system to send a specific cohort of users down one codepath and another and then measure the results against a control group.

When a team chooses to use toggles it’s important to design them with clear labels and standard visual design. They should always be visible, recognizable and deliver an immediate result. Additionally, designers should consider the societal and cultural implications of using the color red to signify an On position as it can have an unintended negative connotation in some cultures.

It’s also wise to test the toggle configuration that will be live in production and any fallback configurations with those toggles flipped Off. Many teams add a task to the backlog for toggle removal after they’re first added and others even put expiration dates on their flags to prevent them from ever being accidentally left in place. This is because toggles can have a significant impact on performance.