A toggle is a switch that allows users to control an aspect of an experience or view. Often toggles are used to manage states such as whether an experience is active or inactive, if content is visible or hidden, or to enable or disable features in software applications.

Using toggles can help teams release and manage changes to their products in a more controlled way. By managing feature toggles in small increments, teams can test the performance and user experience of new features before releasing them to all users. This practice is known as Continuous Deployment and has been used by companies such as Facebook, Etsy, and Google to roll out features in a controlled manner and collect user feedback before making changes to all users.

There are many different ways to implement toggles in code. The simplest is to use an inline comment to declare that an aspect of an application or view should be enabled or disabled. This method is not recommended for larger codebases as it can cause confusion for anyone reviewing the code and is prone to bugs and issues that can take weeks or months to debug.

The best way to avoid these problems is to use a separate toggle switch to indicate that a feature should be activated or disabled. This is usually a button that can be clicked, or in the case of UI elements it might be an image that is shown on or off. This approach can help teams create more readable and easier to maintain code.

In addition to providing a clear signal for when a toggle should be enabled or disabled it is also important to write clearly descriptive labels for each toggle. This helps ensure that both developers and users understand what the toggle does and its impact on the current state of the product. The labels should describe what will happen when the toggle is enabled and should not be misleading. For example, an app should not use a toggle to indicate that content is being downloaded. This would be confusing for users because turning the toggle on does not mean that the downloading will stop. In fact, it would be better for the app to replace this toggle with a checkbox or other form element that requires an immediate confirmation action.

Toggle configuration can be managed in a variety of ways ranging from static files that are hardcoded to the use of preprocessor flags like #ifdef. Once a team reaches a certain scale it is typically best to move the toggle configuration into some type of centralized store, usually an existing application DB. This approach is often accompanied by the build-out of an admin UI which enables system operators, testers and product managers to view and modify the toggle configuration. It is also common for teams to perform some testing with all toggles flipped On to help reduce the risk of surprise regressions in future releases.