Toggle is a simple user-interface control that allows users to change settings, preferences or other states of functionality. When used in a well-defined context toggles can be an ideal user interface component. When used poorly however they can cause confusion and be difficult to understand for users. To avoid these issues we need to be very clear about how toggles are implemented and the context in which they are presented. We should also ensure that they have clear and direct labels and use standard visual design cues. Moreover we should provide immediate results when the toggle is pressed, ideally within a few seconds.
Toggles can be implemented in many different ways but most importantly they should be configured in a way that is consistent across all systems and that enables us to manage the corresponding config reliably. For example using static files to store the toggle configuration quickly becomes cumbersome once you reach a certain scale because it is difficult to track and change the config consistently across all servers. In order to address this issue many companies choose to move the toggle configuration into some sort of centralized repository, often an existing application DB, and then build-out a admin UI which allows system operators and testers to view and modify feature flags and their configuration.
The main advantage of this approach is that it is much easier to test and verify the toggles since they live side by-side in source control. Another advantage is that it is much easier to make data-driven optimizations by modifying the state of a toggle and then observing the impact on specific cohorts. This technique is commonly referred to as multivariate or A/B testing and is a key ingredient of an Agile development process.
Toggle also makes it easy to create different variants of the same feature, called Experiment Toggles, by adjusting only one or two variables such as the button text, label, and color. This is a great way to try out multiple different configurations of the same feature and learn which ones work best before making a full-scale rollout.
It is important to note that a Release Toggle should generally not stick around long, although product-centric toggles can remain in place for longer periods of time. This is because a Release Toggle is not meant to be permanent and is instead used to make transitionary improvements for specific cohorts of users. Once the experiment has completed rolling out a new version with the updated toggle should be rolled out for the remaining members of that cohort.
A Toggle can also be used to implement a Champagne Brunch, which is an alternative to a Canary Release for exposing new features to a small group of users while keeping the rest of the population on an old version. This is typically done on a very limited basis and should not be confused with an actual Permission Toggle which is used to expose features to premium users only.
