A toggle switch is a form of user interface control that provides users with the ability to select between two opposite states. When used appropriately, it can be a great way to update preferences, settings, or other types of information in your application. When used incorrectly, however, it can be a frustrating user experience. To ensure that your toggle switches are working as intended, be sure to provide clear labels and standard visual design.

The word toggle is a verb that means “to alternate or shift between states.” The 18th century definition of the term was “pin passed through the eye or bight of a rope as a fastener.” Today, we use it mostly to refer to a pin-shaped device that can be used to secure a cord or rope. The word also refers to a type of up-and-down switch, such as the one on your caps lock key.

Toggles are a common feature in software development. They are used to implement A/B testing and multivariate experiments by allowing developers to dynamically re-configure specific service instances. For example, an experiment could be configured to send users down one codepath or the other and then compare their behavior. This is a great tool to help with testing, debugging, and providing more personalized experiences for your users.

When implemented correctly, Toggles allow you to test a variety of different versions of your application without requiring the entire codebase to be deployed in order to test them. This is particularly useful in situations where you need to test with different devices or environments, but don’t want to completely redeploy your codebase for each new variation. However, using Toggles to re-configure service instances can become cumbersome once your application scales and you need to make changes across a fleet of servers. At that point it’s best to move to some sort of centralized configuration system.

The easiest way to manage your feature flags is by using an external service that can handle runtime re-configuration. This will eliminate the need to deploy a whole new version of your application and allow you to re-configure specific service instances at will.

This is also an ideal solution if you have multiple developers working on the same application or service. If you don’t have a robust distributed configuration system in place, it can be extremely difficult to keep track of the various toggle configurations that each developer is changing. Additionally, if your toggles are based on static files you’ll have to constantly upload these files into your testing environment to make changes, slowing down your CI/CD cycle and limiting your ability to experiment with different features.

Finally, it’s important to note that while toggles can be a great tool for your product they can also be a source of frustration for people with accessibility needs. Many web developers and designers simply don’t understand accessibility and use toggles in ways that are unusable by users with screen readers or other assistive technologies. Be sure to follow the guidance in WCAG 1.4.1 when creating your toggles to avoid any confusion for your most vulnerable users.