A toggle is a piece of wood or plastic that’s sewn to something like a coat or bag and pushed through a loop or hole to fasten it. In computers and some machines, a toggle switch is used to change the function of a component or feature. He toggled the com to talk to air traffic control.

In software development, a toggle is a feature flag that lets you disable or enable features in release builds without having to change the codebase. Traditionally, new features were written on separate code branches for each release in the waterfall model, but using toggles, your team can perform all of the same development and testing process right on trunk code.

Toggles are also a great way to support agile approaches to software development. By defaulting to a Canary Release or Champagne Brunch mode, you can expose a set of users to a new feature before the majority of your user base. When the feature has proven itself, you can then change the toggle state to “on” and roll out a new version with the upgraded functionality.

As with all UI components, be sure to use toggles sparingly and for the right purposes. Avoid toggling large swaths of the codebase and make sure there’s a process in place for pruning toggles as they expire, otherwise you may end up with confusion for your teams and a debugging nightmare weeks or months down the line.