A toggle is a switch that has two positions, one of which turns things on and the other of which turns things off. It is found in hardware (like the keyboard’s Caps Lock or Num Lock keys) and software, such as options menus or setting screens. The term also can be used as a verb, to describe the process of switching between two functions at the same time: “I toggled between the maps and streams of the game.”
A simple user interface element, toggles are useful for updating preferences, settings or other types of information. They should be designed with direct labels and standard visual design to ensure clarity for users. Toggles should use color to indicate their state, and it is important to consider contrast and cultural implications when selecting colors for these visual signifiers. For example, red can be counterintuitive for users who associate it with stop signs or traffic lights.
Toggles are often used to manage complex features or to expose them for limited durations to a small number of customers (similar to Canary Releases). In this case they may be short-lived and should be managed in the same way as other feature flags, through the CI/CD pipeline. This usually means adding a task to remove a toggle from the backlog when it is no longer needed. Some teams even go as far as to put an expiration date on these toggles in order to prevent them from hanging around for too long.
Managing the configuration of a toggle at a large scale can become cumbersome. In addition to introducing an additional step in the deployment cycle it can be difficult to maintain consistency across a fleet of servers. This is why many organizations move their toggle configuration into some type of centralized store, often an existing application DB. This is generally accompanied by the build-out of some form of admin UI that allows system operators, testers and product managers to view and modify toggle configuration. It’s also worth mentioning that while static configuration is typically preferred there are some cases such as Permissioning Toggles that require a more dynamic approach that includes the ability to change the toggle state at runtime. This could include using a preprocessor’s #ifdef feature or creating an endpoint that allows for dynamic in-memory re-configuration of the toggle. This can provide a much more efficient way of working at a larger scale. However, it is crucial to understand that this will increase the cycle time for changing a toggle state and thus impact the overall validation cycle of your system.
