A toggle is a switch with two positions, on or off. It is used in a wide variety of electronic, mechanical, and computer-related devices to control or bind things together temporarily.

The word can also be used as a verb meaning to shift back and forth between settings, modes of computer operation, or other options. For example, if you are videoconferencing with two friends at once you may use toggles to alternate between screens and keep one conversation private from the other.

In software development a Toggle is a Feature Flag that has been set to ON or OFF. When a Toggle is ON it means that the feature is available to be enabled in your production environment. In contrast, if the Toggle is OFF it means that the feature is not available and will not be activated.

Toggles are important tools for the modern software developer as they provide a way to control the flow of features into production. A Toggle is similar to a Canary Release in that it is a limited audience feature but differs in that it allows for dynamic in-memory re-configuration during runtime.

The most common use of Toggles is to enable or disable experimental features in production. When a product is in an early stage it is often helpful to limit the number of features that are exposed to users. By using Toggles a team can easily roll out new versions of their application with experimental features turned ON or OFF. Unlike Canary Releases where the toggling decision is baked into a release a Toggle will typically remain in place for much longer (although it should still be transitionary by nature).

It is important for teams to be proactive about deprecating and removing old Toggles that are no longer needed. This can be done by adding a task to the backlog for the team to remove a Toggle when it is no longer in use or by creating a time bomb that will fail a test or even refuse to start a service if an expired Toggle is detected.

When designing a toggle it is essential to use clear labels that describe what the switch will do and what state it is currently in. This will ensure that users understand what is happening when they interact with the Toggle. For example, using a high-contrast color for the active state is effective and avoids confusion. However, the choice of color should be carefully considered in light of societal and cultural differences.

It is also important to note that a Toggle is not a replacement for a checkbox or radio button in form fields. For example, if you are using a Toggle to control the visibility of sent emails in a chat app you should probably replace it with a checkbox rather than a toggle. This is because the user should be able to immediately see the results of their interaction with the interface without having to submit any kind of change request.