A toggle is a switch that allows people to manage the state of something—as in, whether it’s on or off. It is used in every aspect of computing when there are options or preferences. A toggle is often represented by an icon, but it can also be a button or other widget.
A common use case for toggles is to provide a means of changing the default settings in a software program. This may allow the user to customize an application to fit their needs, such as by adjusting its font size or color. Toggles are a great way to provide this functionality without creating a completely new program or changing the core code of an existing one.
While there are a few variations on this basic model, most toggles offer two outcomes: A or B. In a web application, this can be seen as a radio button or checkbox—although it’s important to note that a toggle is only truly effective when it is the sole element on a page. In other words, multiple toggles cannot be opened at once; once one is clicked on, the others close automatically.
In addition to providing a simple, straightforward interface, toggles can be very useful for implementing progressive delivery in software systems. By allowing teams to enable or disable features at will and without needing to restart the process, it is easier to test changes in a production environment. This can help to reduce the risk of releasing untested code into production and can make it more feasible to adopt Agile development practices such as continuous integration and continuous deployment.
Another common use case for toggles is in experimental testing of new features and improving product quality. By using a feature flags system to control the state of a feature it is possible to compare the impact of different code paths on customer engagement, user experience, and other metrics. This technique is commonly referred to as “Multivariate Testing” or A/B testing. A toggle is a powerful tool for this type of analysis because it can be easily enabled or disabled to compare the effects of alternative code paths on specific cohorts of users.
When implementing a toggle based progressive release process it is important to understand that the configuration of a toggle lives side by side with its counterpart in source code. As a result it is critical to be able to perform automated tests against a toggle with both the original and new configuration – similar to a Canary Release or Champagne Brunch.
Savvy teams consider the toggle configurations that are live in production to be inventory which comes with a carrying cost, and therefore seek to minimize the number of toggles. Some teams even go so far as to include an “expiration date” for their toggles and will fail a test (or even refuse to start the application!) if a toggle is still flipped On in production after that expiration.
