Toggle is a term used to describe any switch that only has two positions — on or off. Typically these switches are small and can be easily manipulated by users through simple actions such as clicking or pressing a button. When designing software for user interaction with toggles, it is important to focus on both the physical and visual signals that a button or switch has reached its desired state. For example, when using a color to signify the state of a toggle it is important to make sure that the color contrasts well with its neighboring elements and that it also has appropriate societal and cultural significance for your audience.

Toggles are often used to enable or disable new functionality within a system. This type of feature is usually only available to a specific group of users and should be clearly communicated to those individuals so that they can be aware of the impact of their choice. Toggles can be very effective when applied to user interfaces where it is important to keep the number of options low and deliver immediate results.

Savvy teams view the Feature Toggles in their codebase as inventory that comes with a carrying cost and seek to manage this by being proactive in removing toggles as they become unnecessary or deprecated. In addition to ensuring that toggles are clearly labeled and easy to understand a team should focus on leveraging them in a consistent manner to help prevent users from being confused or surprised by unexpected behaviors.

When implementing Toggles in production it is important to test the toggle configuration that will be live in production. This will typically require testing the current production toggle configuration plus a fallback version where all of the planned release feature flags are flipped Off. It is also a good idea to run some tests with all of the planned feature flags flipped On to help detect any unexpected regressions.

When developing a new system it is common to use a Champagne Brunch style of release strategy where a large portion of the population is exposed to a feature before it is rolled out to a wider cohort of users. This allows for quick iteration and feedback loops which can be difficult to do when a feature is being introduced to the entire population at once. In these types of releases it is sometimes useful to implement a per-request toggle that can be triggered by an experiment to dynamically re-configure the specific service instance for a particular user.