A toggle is a switch that can be pressed or clicked to change between two states or options, such as turning on and off a feature in a mobile app. Toggles are often used in everyday technology and software applications to enable or disable features, and they are especially useful on mobile devices because they take up less screen space than two radio buttons or checkboxes. In programming, a toggle is typically represented by a Boolean variable that can be set to either True or False. A toggle is a better choice than a checkbox for changing system settings and preferences because it enforces a mutually exclusive state (on or off). Toggles are also the preferred control when the user needs to select one of multiple possible values, such as whether Airplane Mode is ON or OFF.
A common misconception is that a toggle’s name should always be capitalized, as in “Feature Toggle.” However, the word toggle can be lowercase, depending on its context and meaning. For example, the name of a toggle that manages which features are available to specific users may be written in lowercase letters to make it more visible, while a toggle describing the state of a particular service instance could be written in uppercase to highlight its importance and urgency.
In practice, it’s best to use lowercase toggle names whenever possible. This ensures that the toggle’s purpose is clearly understood, and it can be found easily in a code base. In addition, this approach is easier to work with at scale, as it reduces the amount of syncing required between developers and allows teams to work on a smaller number of files.
Toggles can be managed in a variety of ways, from static files to centralized DBs. In general, it is better to use a centralized solution, as this will reduce the likelihood of configuration errors or mishaps in production environments. In many cases this will be accompanied by a built-out admin UI which is easier to manage for system operators, testers and product managers.
During the design process, it’s important to consider how a toggle will be configured at scale and how it will be managed once it is deployed. In our experience, it is best to configure a toggle via a centralized config system, which will be easier to manage and ensure consistency across deployments. Alternatively, some organizations may choose to hardcode toggle configuration into static files. This can be effective for some toggles, such as Ops Toggles, but it should be avoided for more dynamic flags, as it will make re-configuration more difficult.
Regardless of how a toggle is configured, it is essential to give it an informative name that makes sense for the intended audience. The name will help the team maintain consistency across releases and understand how a toggle should be set. For example, a Canary Release might be named “Canary Release,” and an algorithm that is too resource intensive for the general user population might be called “Champagne Brunch.” In this case, it would be appropriate to name the toggle “Permissioning Toggle.” As we discussed in our previous article on naming best practices, there are four general categories of Feature Toggles that should be managed differently, but this category is an excellent place to start.