A toggle is a switch between two different settings or options; you can use one to change a feature on or off. It can be used in software, hardware, or even in everyday life. A toggle can be physical, such as the knob on a light or a switch on a door; it can also be virtual, like the on/off button in an email program. It’s a simple control, but it can have a big impact.

The word “toggle” is often derived from the physical action of pushing or pulling on a switch to move it between its positions, as in a rocker switch on a car or a mechanical door lock. But you can toggle in other ways as well, such as when you swap between two screens while video chatting with friends, or when you switch back and forth between work and home tasks. You can toggle between programs by pressing the Alt+Tab keys or switching between windows in your computer.

Using toggles is a powerful way to expose and manage features that are currently in transition. But it’s important to design them with care and consistency so that users understand what each toggle does, how to activate it, and what happens when they do. Toggle controls should look like sliders and utilize visual cues (movement and color) to avoid confusion. And they should deliver an immediate, recognizable result when activated.

Toggle configuration can be stored in static files, but that method becomes cumbersome at a certain scale. It’s also difficult to ensure that toggles are flipped consistently across a fleet of servers. Savvy teams therefore prefer to use some form of runtime feature flag management that enables them to dynamically re-configure individual service instances based on a toggle state.

When designing a toggle, the choice of color is critical. Contrasting colors make it easier for users to recognize the difference between an active and inactive state. In contrast, a low-contrast color can be hard to perceive and may even confuse users. Also, be sure to consider societal and cultural implications when selecting your toggle color palette.

While Release Toggles are often short-lived compared to other categories of Feature Toggles, Permissioning Toggles can be quite long-lived. In some cases a permissioning toggle will be in place for multiple years before it is rolled out to a larger audience.

Toggle configuration can be complicated and a challenge to maintain as a team grows. For that reason, it is best practice to build out a robust configuration system with an admin UI for product managers and testers. This can help reduce the amount of manual effort required to test each toggle configuration. It’s also wise to plan ahead for when a toggle needs to be changed and to ensure that all of your tests are passing when the toggle is flipped to the desired state.