A toggle is a button that switches between two states or options. It’s used in technology, programming, and communications to control features that are too complex to be controlled by a single switch.

When used in continuous development toggles allow product teams to experiment with feature rollouts before rolling them out to a larger audience. This practice helps reduce the risk that a new feature release will be poorly received and can also help improve the velocity of deployment cycles by allowing teams to quickly roll back to a previous version if the experiment fails.

Some of the most popular uses of toggles are for A/B testing and multivariate tests. When a toggle is enabled a single user will be sent down one codepath over the other. This can be useful for making data-driven decisions on things like the checkout flow of an ecommerce system or the Call To Action wording on a button.

The best practice for naming feature flags is to use descriptive names that give some context about what the toggle does or why it was created. This will make it easier for someone else on the team to understand why a change was made, what its impact will be, or how long it has been in place without reading the source code.

A toggle’s configuration can be managed with a number of different techniques, ranging from the simple but less dynamic approach of commenting (like if>else>) through to approaches that are more flexible but require more effort when deploying the artifact. Some of these solutions also have the downside of requiring some kind of runtime modification in order to re-configure the toggle, which can be difficult and expensive to implement in environments that do not support feature flags.