A toggle is a switch that can be set either on or off. In software it’s often used for options menus but can also be found in hardware like the keyboard’s caps lock and num lock keys. The term is also applied to any button or other interface element that can be flipped between states.

Toggles are a great way to enable A/B testing on live products. They can be used to allow engineering teams to test new code or features without impacting users. Once a toggle is on engineers can monitor how well the feature performs and even rollback features when necessary.

For example a team might want to test an experimental variation on their login flow where they would only enable the new feature for logged in users. This could help the product team understand how this change affects their user base before committing to a full-scale implementation.

Feature Toggles can be used in other ways to drive data-driven optimizations. For example a team may wish to experiment with different variations of the purchase flow on their ecommerce website or the call to action wording on their login button. These experiments can be run using a Toggle Router which consistently sends a cohort down one codepath or the other. The cohorts can then be measured and the result analyzed to see which version drives the best conversion.

When creating feature toggles it’s important to give each toggle a meaningful name. This can be helpful when communicating with developers in other teams or when writing error messages about specific toggles. A meaningful name can help identify who wrote the toggle, when it was written and what it does. It can also make it easy for a developer to find the relevant toggle configuration when they’re debugging or testing a particular service.