What Is a Toggle?

Toggle is a hardware or software switch that allows a user to easily move back and forth between two settings. For example, the Caps Lock and Num Lock keys on a keyboard are toggle switches that are pressed once to activate the feature and then pushed again to turn it off. The word toggle can also describe the way that a user switches between multiple screens as they video chat with two friends simultaneously.

Savvy teams often use toggles to perform multivariate testing on a release. By putting each user into one of several cohorts and then dynamically re-configuring the codepath that a particular customer will take based upon their cohort the team can measure the effect of different configurations on performance or conversion.

Using a feature toggle to manage this type of testing can be cumbersome when it starts to scale. In order to alleviate this issue many companies choose to move the toggle configuration out of static files and into some type of centralized store, often an existing application DB. This move is usually accompanied by the build-out of some form of admin UI which will allow system operators, testers and product managers to view and modify the toggle configuration.

When a team is configuring their toggles they should always be mindful of the visual design of their toggles. For example, the color used to indicate a toggle’s state should be chosen carefully. It’s important to consider contrast and cultural implications when selecting a color to ensure that users can reliably discern the toggle’s state. Additionally, it’s important to provide clear labeling on a toggle that indicates what the switch will do when the toggle is flipped on or off.

Finally, it’s important for a team to test the toggle configuration that they expect to become live in production. For this reason, it’s common for teams to test their releases with all of the toggles that they intend to release flipped on. This will prevent any surprise regressions that might happen when the release is pushed out to production. Some teams even go as far as to put expiration dates on their toggles in order to make sure that they don’t leave old or unnecessary flags hanging around for too long.