Toggle is a user interface element that allows users to update preferences, settings, and other information. Toggles should be clearly labelled and use visual cues to convey the toggle state. They should also change position as the user updates their preference.

In computer science, a toggle switch (also called a toggle button) is a hardware or software component that switches the state of its associated function between two outcomes. For example, the Caps Lock and Num Lock keys on a keyboard are toggle switches that allow the user to turn on or off various functions of the computer.

On the Web, toggles are most often used for changing between states in a widget or application. They’re typically shown as a button that either has an on or off icon or a text label, and they’re clicked to change the state. Toggle buttons should be clearly labelled and use visual cues for the toggle state, such as movement or color.

In the context of a feature flag, a toggle can be set to either “On” or “Off.” Savvy teams think of their toggle configuration as inventory that comes with a carrying cost and seek to keep it low by being proactive in removing toggles once they’re no longer needed. This is especially important when using more dynamic toggles such as those used for Champagne Brunch or Canary Releases that require a manual code deployment in order to flip them. In these cases it can be much faster to re-configure the codebase rather than wait for an override of an existing toggle.