A toggle is a switch with two positions, either on or off. A common example of a toggle is the Caps Lock and Num Lock keys on a computer keyboard which turn specific functions on or off. The term is also applied to software settings which are configured in a similar way.

Many teams struggle with the complexity of managing toggle configuration as their application scales and the ability to toggle a feature on or off becomes more complicated. There are a range of solutions to this problem from relatively simple (but less dynamic) approaches like hardcoding toggle configuration in static files through to more sophisticated approaches which allow runtime configuration via an API.

Savvy teams view their Feature Toggle inventory as an asset which comes with a carrying cost so they work to keep this inventory as low as possible. To achieve this they often perform regression testing against a production toggle configuration which has all of the toggles that they expect to release flipped on. In addition they may add tasks to their backlog for removing toggles from the codebase once they’ve been deemed no longer necessary. Some teams also implement “expiration dates” on their toggles which will trigger a test failure if the toggle is still around after an expiration date has passed.

When designing and implementing user interfaces that use toggles it’s important to ensure that they are well designed and provide clear feedback on the current state. This includes using high-contrast colors to signal states and ensuring that the states themselves are descriptive, clear and unambiguous.