The word toggle means to switch between two opposing states (like ON and OFF). In software engineering a toggle is a feature flag that allows a team to enable or disable functionality during development, allowing them to meet delivery deadlines. Toggles are a great choice for changing settings or preferences and they generally work better than radio buttons in mobile apps since they take up less screen space. Toggles should also be used when the change in state is a one time action that doesn’t leave any persistent data behind. Otherwise you should use a checkbox instead to allow the user to choose between options.
The most common use of a toggle is in an A/B testing scenario. An A/B tester will set up a test environment with both a normal version of the software and the experimental version. Each of these versions will be configured with a different toggle which will determine which codepath the system will send a given user down. At runtime the toggle will be flipped to the appropriate state based on which cohort the user is in.
There are a number of ways to configure a toggle, with some approaches being simpler but others requiring more complex infrastructure or even full scale code changes. The most straightforward approach to toggle configuration is by hardcoding it in the source code using a commenting strategy such as the #ifdef statement in a programming language (where available). This is not ideal as it will require every deployment to update the application to reflect the new toggle state and can be very time consuming, but is a good solution if you want to avoid any additional infrastructure costs.
A more sophisticated way to configure a toggle is to use an API or config file to manage the state. This is the preferred method if you want to avoid having to deploy a full-scale code change in order to toggle a feature on or off. However, this does require some additional complexity and can be more expensive in terms of testing, maintenance and operations.
When using toggles in your UI design it’s important to have clear and direct labels and to make the current state of the toggle obvious. You should also always use a high-contrast color to indicate the state and make sure that your platform supports this approach. Moreover, you should consider the societal and cultural implications of your toggles’ colors. For instance, using red for an ON toggle could be counterintuitive to users in some cultures as it may be associated with stop signs or traffic lights. Also, be aware that using toggles for downloading content can mislead users if you don’t include a download count and clear information about how to end the download process.
