A toggle is a control that allows people to select between a pair of opposing states (like on and off) using a different appearance for each state. Toggles can be found in hardware and software — the Caps Lock and Num Lock keys on keyboards are toggle switches that let people switch between two functions. In software, toggles are often used in conjunction with checkboxes and radio buttons to form larger controls that can represent multiple options. It’s important to note that even though toggles can have different appearances across platforms they should all follow the same basic guidelines, including a clear, consistent meaning and visual signifiers for each state.

It’s common to use experiment toggles to test new features with real users before committing to rolling them out for everyone. For example a team might create an experiment toggle that allows users to opt-in to a premium product feature for a period of time before deciding whether to permanently make it available. This is similar to a Canary Release but with the important difference that it’s generally permanent, at least on a per-user basis.

Savvy teams look at Feature Toggles as inventory that comes with a carrying cost and seek to keep their number of toggles under control. This typically requires being proactive about removing toggles when they’re no longer needed, and some teams even add an item to the backlog for this purpose. To reduce the risk of unexpected regressions when a toggle configuration does get rolled out to production it’s also wise for teams to test with all of the toggles they plan on releasing flipped On.