A toggle is a physical switch, found on many electronic devices, that allows users to manage the state of something. Toggle switches are useful because they can be used to hide or reveal information and actions to users without disrupting the user experience. When used appropriately, they can provide a powerful and efficient way for developers to introduce new features and make changes that affect the entire user base without risking stability and performance.

When applied to software development, the concept of a toggle is often referred to as a feature flag. Unlike traditional branching or versioning, feature flags allow software teams to develop and test new features on their own. These new features can then be hidden with a toggle until they are ready for release or market testing, and then reintegrated into trunk code. This is a significant improvement on the more traditional waterfall development process and makes agile methodologies more feasible for smaller and mid-sized companies.

Traditionally, feature flags have been used to allow for A/B testing on specific segments of a user population. In these scenarios, a company might want to introduce a new widget but doesn’t have enough data to determine if it will be successful before investing in the production code. With a feature flag, a team can quickly roll out the new widget to a small segment of their customer base and gather performance data before deploying it to the entire user base.

In addition to A/B testing, feature toggles can also be helpful for reducing the amount of code regression that occurs when a company releases a major update or bug fix. Typically, regressions are caused when a change is made to an application and the new functionality has unintended side effects on existing functionality. By placing the change behind a feature flag, an entire set of bugs can be identified and eliminated before it is rolled out to the public.

Although it may be tempting to place large swaths of code under the control of a complex series of toggles, it is important to keep the use of feature toggles as restricted as possible. Too many overlapping toggles can lead to complicated conditional logic in the code that can hinder readability and degrade performance. If left unchecked, this can become a massive problem that requires weeks or months of effort to debug down the road.

Toggles that aren’t properly managed can cause accessibility issues for your users. This can be a big problem for those using screen readers or other assistive technologies. For example, if you are using a toggle with a color to indicate its status (such as green for “on” and red for “off”), be aware that some people have red/green color blindness and will not be able to distinguish the difference between these colors.

Another drawback of toggles is that they increase the complexity of your codebase and require additional testing to ensure that each toggle has the desired effect. To avoid these problems, it is important to create a system of managing feature toggles that includes automated processes for detecting and pruning old ones once they have run their course.