A toggle is a binary switch that has only two possible outcomes: on or off. They are used in many everyday technology devices to control things like WiFi and Bluetooth(r) or in software applications to enable and disable features. The term toggle is also used to describe a programming technique that switches between different codepaths when the state of the application changes.

Using toggles in your applications allows you to quickly and easily change the behavior of the application when that behaviour changes. They allow you to experiment with different features without deploying them to all users and can be especially useful for testing A/B tests.

There are four general categories of Toggles which we will explore in more detail below. Each of these can be used for different purposes in your application, and each has its own set of best practices to follow.

Permission Toggles are used to manage permissions for users on a per-user basis. This can be useful for providing different experiences to Premium and Non-Premium customers, or to provide a way to temporarily disable a feature for an entire user base in the event of a bug or security incident.

Experiment Toggles are a great way to perform multivariate or A/B testing on the production version of your application. You can split your user base into different cohorts and then use a Toggle Router to consistently send each cohort down one or the other codepath. This can be a quick and effective way to make data-driven improvements to things like the purchase flow in an ecommerce system or the Call To Action wording on a button.

In most cases it’s a good idea to name your Toggles with some meaningful information that someone on your team can understand. This can help them remember what the toggle does and where it came from, as well as allowing them to be more productive when debugging or modifying that toggle in the future. A simple example of this would be to include the version number in the toggle name, as well as a description of what it does and why it’s needed.

It’s important to be proactive about removing unused Toggles from your application codebase. Savvy teams treat their Feature Toggles as inventory that comes with a carrying cost and try to keep that inventory low. Some teams have rules in place to add a removal task onto their backlog for every new toggle that’s added, while others put expiration dates on their Toggles so they will fail a test (or even refuse to start the application!) after a certain amount of time has passed.

Using toggles can be very beneficial for your development process, as it allows you to move more quickly through the testing and QA phases than might be possible with traditional waterfall or agile approaches. However, using them too liberally can cause cognitive issues for your users and lead to confusion in shared development environments.