A toggle is a switch that has two positions, on and off. It is used in technology, computing, programming, and communications to provide a simple way for users to change settings or modes. In software, toggles are often a simpler alternative to radio buttons and checkboxes.

Toggles are very popular in mobile applications and can be useful for adjusting system settings or preferences (i.e. states of system functionalities). They can also be more user-friendly than two radio buttons in a row because they take up less screen space. However, they can be confusing for users if not designed well since they do not have an explicit label that tells the user what state the toggle is in.

In order to make toggles more user-friendly, designers often add color changes or animation to help signal the toggle’s state. This is a good idea in general, but there are two important things to keep in mind when using this technique: 1. WCAG recommends that we “don’t rely solely on color for conveying meaning”. 2. Many users have visual disabilities or cultural associations with colors that may not be obvious to designers.

Another reason to use toggles is to perform multivariate or A/B testing. A toggle router can consistently send a cohort of users down one code path over the other, and then track the aggregate behavior of each group to compare performance. Toggle configurations are often stored in static files, but as the number of toggles grows it becomes difficult to modify them reliably, and centralized management is recommended. In order to simplify this process, many organizations build out a dedicated admin UI or application DB for managing feature toggles and their configurations.