A toggle is a switch that allows a user to set an option to either ON or OFF. Toggles are often used to update preferences or settings and are a good alternative to radio buttons as they take up less space. Toggles also enforce a mutually exclusive state so they are more cognitively friendly than checkboxes which can enable multiple states simultaneously.
While a toggle is simple to implement it’s important that it is used consistently across all pages and services. This will help to keep the user experience consistent and reduce confusion. When using toggles it’s important to ensure that they are easy to understand, use standard visual design, and deliver immediate results. A great way to do this is by providing clear labels and ensuring that each toggle has a unique name.
One of the most common uses for a Toggle is to perform multivariate testing (also known as A/B testing). By having different cohorts of users be directed down different codepaths you can measure the effect that each has on user behavior. This allows you to make data-driven optimizations to the system without impacting all users. Toggle Routers are a commonly used tool for doing this.
Another way a Toggle can be used is to provide premium features. By having a toggle switch that is only exposed to a small subset of the user base you can prevent a feature from being widely implemented without having to delay its rollout. This is called a Champagne Brunch release and it’s similar in many ways to a Canary Release but with the distinction that it is only available to paying customers.
A Toggle can also be used to manage a specific feature in a production environment. This is called a Permission Toggle and it’s used to limit the exposure of a specific feature to a subset of the user base. This is useful if you have an existing product that you want to test but don’t want to expose a new feature to all of your users. A Permission Toggle can be very long-lived compared to other categories of Feature Toggles such as Canary Releases because it’s only switched on and off on a per-request basis.
Managing Toggle configuration is typically done via some form of distributed configuration management system. There are a number of different approaches to this from very simple but less dynamic (like commenting) through to more sophisticated systems that offer features like per-request toggle reconfiguration. Many teams have some type of administrative UI for managing Toggle Configuration which allows product managers, testers and engineers to view, modify and debug the configuration.
Savvy teams recognize that each toggle in the codebase has a carrying cost and they should be proactive about removing the toggle when it’s no longer needed. As such some teams have a policy of adding a task to their backlog for removing a toggle when it is first introduced. In addition, many teams also perform some tests with all of their toggles flipped On and others with all of the toggles flipped Off to avoid any surprise regressions in the future.
