A toggle is a feature flag that allows you to enable or disable the behavior of software in a controlled way. It is often used to avoid regressions in production or to allow developers and testers to experiment with features without impacting the experience of users in a shared environment.

Toggles can be found in everyday technology, from physical switches like light bulbs or electrical outlets to software and application toggles that allow you to switch between different modes or settings. They can also be used to manage the responsive design of your website and web applications by changing layouts and display options based on screen size or device type.

While toggles are great for managing a large number of features on a single page or within an app they can have issues when used in larger applications where the toggle can be flipped by many users at once. In these cases a more granular method of controlling the state of a feature should be considered such as an accordion or collapsible section. While these can have the drawback of requiring some initial user investment they will typically provide better performance in terms of both speed and accessibility.

When implementing a toggle it is important to consider that users will need clear visual feedback about the current state of the toggle. This can be accomplished through color changes or clear text indicating which state the toggle is in. It is also important to consider societal and cultural issues when choosing colors for toggle states in order to avoid confusion. For example the color red is a common choice for On and Off but it can be confusing to some cultures who associate red with stop signs or traffic lights.

Using static files to manage toggle configuration can become cumbersome at scale and ensuring consistency across a fleet of servers can be challenging. In response to this many organizations choose to move toggle configuration into some sort of centralized storage, often an existing database. They may also build out some form of admin UI to allow for system operators and testers to view and modify the configuration.

Testing with toggles

It is important to test the toggle configuration that will be released to production. This means you should test with any toggles that you intend to release flipped Off and also with any toggles you want to keep flipped On. It is often a good idea to also test with all toggles flipped Off as this will help prevent any surprise regressions from being introduced into production by future releases.

When a bug is fixed it can be tempting to create a feature toggle around the buggy code to prevent any unexpected side effects. However, this can be a risky strategy. If a toggle is not correctly designed it could lead to further problems and a more complex bug fix. Creating a toggle should only be done when it is clearly necessary and will not significantly increase the complexity of the bug fix or the overall size of the change.