Toggle is a user interface element that represents a switch between one state and another. It’s found in nearly every option or preferences menu and can also be used to change the state of a feature (either ON or OFF).

In software toggles are generally used when there is a clear distinction between two opposing outcomes such as an ON or OFF setting. It is the preferred control when a user needs to update their preference or settings because it allows them to quickly and easily make a decision by clicking either ON or OFF.

A toggle can be found on physical hardware such as keyboards where the Caps Lock and Num Lock buttons are toggles which allow users to change an existing function’s state from Off to On or vice versa. Toggles can also be found on web pages and apps where users are able to select between two opposing options, for example when selecting whether to show or hide the Cookie Notice.

Using toggles is a great way to manage feature flag configuration and ensure that only the correct version of a codepath is running in production. Using a toggle is also an effective tool for testing and iterating a site or app by exercising different code paths. This is a technique known as Cohort Toggling or A/B Testing and can be applied to everything from the call to action wording on a button to the purchase flow of an ecommerce system.