A toggle is a switch between two opposing states. It can be used to control system settings and preferences, or it can be a user-interface element in an app that allows users to choose from a set of options.
The 18th century meaning of a toggle is “pin passed through the eye of a rope to hold it in place.” It’s still used today for a similar type of fastener, and also for an up-and-down switch like a light switch. In computer technology, a toggle is an on-off command that is often found in options menus.
A toggle switch can be a useful component for changing settings or preferences, but it should be used sparingly. Toggling switches take up screen estate, so they should be limited to instances where the state of the toggle is not critical to user experience or when they can be updated quickly and easily.
Labels for toggle switches should clearly describe what the control will do when it is on and what state it is in right now. Ensure that the label is clear, short, and direct.
Toggles should be visually distinct, using colors that match the underlying state of the control (e.g. red for the on position and green for the off position). Colors should contrast with each other to make the switch easier to read and recognize.
While many teams manage toggle configuration by hardcoding it into static files this approach is fairly fiddly and doesn’t work well for feature flags that change dynamically – at least not without adding a lot of extra complexity. It is preferable to manage toggle configuration in some kind of centralized store, often an existing application DB, and provide an admin UI for system operators, testers and product managers to view and modify feature flags and their configuration.