A toggle is a button, switch or control that allows users to set an option into one of two states. They’re commonly used in technology, computing, programming and communications to allow users to change settings or modes. Typically toggles are used to enable or disable features in applications, operating systems and hardware. They’re also used to enable and disable features in web applications, websites, services and platforms.
A great example is the Caps Lock or Num Lock key on a keyboard. They allow users to toggle between enabling or disabling these functions on the keyboard. Toggles are also used in software to change options and settings, often using standard visual design elements to make them clear and consistent.
In general, toggles should be used for settings which will have a direct and immediate impact on the user. This includes preferences and settings, but also anything which can cause a significant difference to the user’s experience of an application such as themes, layouts or performance improvements.
As well as providing direct and clear feedback to the user, toggles are also a great way of managing complexity within your application. They can be a useful tool for rolling out new features to select segments of your user base or as circuit breakers in production code.
Often toggles are configured via static files or some other form of hardcoding, this can be fine at small scale but becomes difficult as the number of toggles grows and the size of the user segment that you want to test with them increases. It can also be difficult to ensure consistency across a fleet of servers as the configuration of each toggle changes. For this reason many organizations opt to move toggle configuration into some type of centralized store, often an existing application DB. In conjunction with this they will usually build some form of admin UI which allows system operators, testers and product teams to view and modify feature flag configuration.
In addition to this it’s important to consider how you indicate that a toggle is active or inactive. Depending on the context this can be as simple as using a bold/thin font combination to show the difference or as complex as using animations and other visual cues to convey status. It’s essential to ensure that toggles are always clear and consistent. For example, if you use green as the “on” state and red as the “off” state, you’ll need to make sure that these colors are clearly distinguishable from each other so that a user with color vision deficiency can understand what action is required.
Feature toggles are a valuable tool in any continuous delivery practice. They can be used to experiment with new features with a subset of your user base or to act as circuit breakers for your production system during high latency periods. The ability to easily roll out/back a toggle helps reduce the risk that a new feature will have unintended consequences and can help you to speed up the cycle of your CI/CD pipeline.
