A toggle is a switch that can be positioned in two states: ON or OFF. It’s a common control found in options or preferences menus across many applications and is also the best choice for controlling system functionality like turning Airplane Mode ON or OFF. Because of this, toggles are often used on mobile where space is limited but the user needs to change a state.
Toggles are a powerful tool but they should be deployed sparingly. It is tempting to overuse them to manage complex scenarios but this can lead to confusing or even broken configurations which are difficult to debug weeks or months down the line. It is also possible to over-provision a set of toggles such that they consume too much memory which can impact overall performance.
When used correctly a toggle is a powerful mechanism to help teams quickly test and deploy changes to their production environments. However it can be easy to overlook the overhead of managing large inventory of toggles and a resulting maintenance burden for teams.
It is wise for teams to have a process in place for managing the lifecycle of their feature toggles. This should include a policy for when to remove a toggle and how to do so. It is also helpful to have a consistent approach to testing which includes exercising all toggles that will be released flipped ON as well as the fallback or default behavior when those toggles are OFF.