A toggle is a switch that can be flipped to one of two possible states: on or off. This type of control is often used for light switches, and it can be found in almost every aspect of software development.

Toggle can be used to test new features before a full release to reduce the risk of regressions and to gather real-time user feedback. It can also be used as a circuit breaker to prevent a complete product rollout from breaking existing functionality. Toggle is a powerful tool, but it’s important to use it responsibly and to have a robust process in place for managing the lifecycle of the toggles you create.

When used in a continuous deployment environment, toggles can help you move faster and reduce your MTTR (Mean Time to Resolve). By using feature-activating toggles, you can hide new code behind them until they are ready for release and avoid having multiple code branches that need to be merged into trunk under more traditional waterfall development models.

Toggles can be used to perform multivariate or A/B testing by setting up a consistent flow of traffic for users in different cohorts, allowing you to measure the impact of different options without disrupting the experience for all other users. This is a great way to make data-driven optimizations to things like call to action wording, the purchase flow of an ecommerce site, or the layout of a page. However, it is crucial to be careful when implementing this type of experiment because it’s easy for old toggles to accumulate in your codebase and become a source of confusion and bloat.