A toggle is a simple control that can be either on or off and typically has a direct effect (e.g. it changes a system setting). This control type is appropriate when your users need to update preferences or settings and for when you don’t want them to have to save or submit a change. Toggles are usually best used for options that don’t have a default value and that need to be changed on a consistent basis, as opposed to one-time choices (e.g. enabling Airplane mode on an iPhone). If you have options that need to be updated often, consider using a slider instead.

A toggle (or toggles) is a piece of wood or plastic pushed through a loop, hole, or eye so as to fasten it. The word is also used for an ornamental rod-shaped button inserted into a large buttonhole, loop, or frog on clothing.

The term “toggle” has become a technical and programming term for a method of dynamically re-configuring specific service instances based on the state of an experiment or other criteria. This is different from the common approach of hardcoding configuration into source code with an #ifdef or similar comment. This type of configuration is appropriate for Ops Toggles and other high-impact features and should be avoided for everything else.

Savvy teams view their Feature Toggles as inventory that comes with a carrying cost and seek to minimize the number of toggles in their codebase. They also strive to be proactive about removing toggles once they’ve been used for the intended transition period (usually a week or two) and even add an item in their backlog to this effect each time a new toggle is added. In some cases teams even put expiration dates on their toggles and use them as a kind of time bomb that will fail automated tests or refuse to start the application when they expire.