Toggle is a common design pattern but has its own set of challenges. The word toggle comes from a mechanical term that means “to change back and forth.” It describes the movement of a lever or switch that can be turned from one position to another, such as a switch that allows you to turn off or on the lights in your home. A toggle is also a tool used to control the flow of electricity or gas in a circuit or a wire.

When designing a user interface, toggles are often positioned next to a label that communicates the current state of the toggle. This setup is easy for most users to understand, but is not ideal when there are multiple toggles on a screen. In this case, users need to be able to read the status of each toggle without having to move their eyes from one position to the other. Toggle switches that are arranged in this way use the proximity principle to help users identify which switch is active. This works well if the toggles look similar and share a single color or a common icon. However, if they are very different in appearance (as is often the case with toggles on a website), it can be difficult for users to determine which toggle they’re pressing and which state that switch is in.

For this reason, it’s important to test the toggle configuration that will eventually be released in production. Ideally teams will test the toggles that will be released with all of them flipped on as well as some tests where the toggles are flipped off. This will help to prevent surprise regressions in the future.

Toggles are also commonly used in experimentation and A/B testing. They can be used to assign a cohort of users to a specific codepath and then track aggregate data from that group. The results can be used to make data-driven optimizations, for example to change call to action wording or button colors.

There are some cases where a toggle may be appropriate, such as when the state of the widget being controlled is not changing in the moment and the users need to manage that state with a simple control. Otherwise, a radio button or checkbox is more suitable.

A final note on toggles: they should always be designed to be accessible. It is easy for web developers to overlook accessibility when using a toggle and end up creating a switch that’s either unusable or confusing for disabled users. For example, the common practice of using only green and red to indicate on/off states can be confusing for those with red/green color blindness.

With these tips in mind, it’s possible to create toggles that are both accessible and clear for all users. Toggle should never be a replacement for a form control, but when used correctly can be a useful way to give users more control over their experience.