A toggle is a switch that has two states, On and Off. Toggles are common in everyday technology devices and software applications and are used to enable or disable features. They’re also a commonly used tool for A/B testing and to perform multivariate tests. For example, an e-commerce company may create an experiment toggle to test different suggestion algorithms in their configurator. Once the test results are conclusive, they can remove the toggle and deploy the winning algorithm to their entire user base.

Feature Toggles are useful for allowing your engineering team to test new code and features in a real-world environment without risking the full application. When a feature is toggled OFF, your users will still see the original version of your application. When the feature is toggled ON, users will see the new feature that is being tested. Using Feature Toggles supports agile development approaches by enabling your team to release software even while they’re working on new features. Previously, these features would need to be written on code branches and undergo a lengthy testing process before they could be merged into trunk code.

When creating a toggle, the key is to use clear, concise labels to make it easy for users to understand what each state does. The label should describe what behavior the toggle controls and which behavior it is currently executing. It’s a good idea to limit the number of words in the label and stick with nouns whenever possible. A good toggle label will convey exactly what state the toggle is in, such as “On,” or “Off.”

Unlike a normal checkbox, a toggle doesn’t emit a checked property when programmematically set. Instead, the value of a toggle is defined by its state, which can be determined by inspecting the toggle’s DOM element or by looking at the toggle’s data in a native form>. If the toggle is part of a form, its label can be submitted along with other form data.

Toggle switches are most commonly used to implement A/B testing. To test a toggle’s effectiveness, it is wise to include both the toggle configuration that you expect to be live in production and the fallback configuration with all of the toggles flipped Off. Many teams also run a handful of tests with all of the toggles flipped On, in case they want to quickly roll back to the existing behavior if a new test shows the need. However, it’s important to note that when all toggles are flipped On, existing or legacy behavior is enabled and any future behaviors will be disabled. This is a tradeoff that must be considered carefully when designing an experiment.