A toggle is a user interface element that provides users with the ability to change system settings or preferences. They are usually used in place of checkboxes because they take up less space and are easy to click on mobile devices. While toggles can be useful when it comes to updating preferences and settings, they should be avoided in cases where users need to choose between two opposing options, such as whether a feature is ON or OFF.

A toggle can be configured by a number of different ways, including setting an environment variable or using an API call. However, in our experience the most robust way to configure a toggle is by using a feature flag. This approach is more reliable than a hardcoded value and allows us to easily change the toggle configuration in future releases.

Toggle configurations should be as dynamic as possible to make the toggle switching experience more responsive and seamless for users. The most important factor in achieving this is the choice of visual cues for the toggle’s state. We recommend using high-contrast colors to signal the toggle’s state, and avoiding colors that have societal or cultural associations. Adding a descriptive word such as On or Off next to the toggle is also a good way to convey the switch’s current state.

In addition to the color and text, the size of the toggle’s font is another critical cue. We found that larger toggles are more recognizable than smaller ones, and the toggle with the lowest font size difference performed worst in our tests. This is likely due to the fact that the difference in font size was not clear enough for users to distinguish between the ON and OFF states of the toggle.

Lastly, it’s essential to test the toggle configuration that will eventually go live in production, as well as a fallback configuration with all toggles flipped Off. Many teams also find it helpful to perform some tests with all toggles flipped On as this helps them detect any regressions that might be caused by future changes to the toggle configuration.

While we generally prefer a dynamic toggle configuration management system there are cases where a more traditional approach is required, such as for Ops Toggles or Permissioning Toggles. For these cases it may be appropriate to hardcode a toggle’s state using a preprocessor’s #ifdef feature, as long as we are prepared to periodically roll out new releases that re-configure the toggle. This approach is more manual and fiddly than a true toggle configuration management system, but it can be a workable solution in these scenarios.