Toggle is a verb meaning “to change or alternate.” It’s commonly used in technology and computing applications to refer to a switch that enables people to choose between two different settings or modes. It can also be applied to an interface button that lets people toggle content or views on and off.
Using toggles in your application allows you to hide or display features based on user preferences and needs without having to make the code changes necessary to support them. This can help you improve the experience for many users while not negatively impacting the experience for a few people who require more advanced functionality.
It’s important to remember that feature toggles come with a cost. Toggles that are left unused in production for an extended period of time can have a negative impact on the performance of your system. Savvy teams look at the inventory of feature toggles as a type of inventory that comes with a carrying cost and seek to minimize the number of idle toggles in their codebase. They do this by adding a toggle removal task to their backlog or building the process into their management platform and managing its lifetime.
Toggles are also helpful for supporting newer agile development approaches such as continuous integration and deployment (CI/CD). Under more traditional waterfall models it’s common for a team to work on a new feature in a code branch and then merge it into trunk code after testing and QA. This process can be lengthy and may lead to code conflicts. Using feature toggles allows teams to develop and test their new features while leaving the master code base in an inactive state until they’re ready for deployment.
A feature toggle can be triggered by a wide variety of conditions including fitness tests from other features, settings in their management software, or even the contents of a config file. This flexibility makes it a very powerful tool for creating a scalable and dynamic feature management architecture.
When a toggle is activated it should be immediately obvious to users what it’s doing and why. It should also be clear which setting or view the toggle affects. Ideally, the toggle icon communicates this information visually, and it should be updated when the toggle’s state changes. This approach can be more cognitively acceptable than checking boxes or radio buttons that rely on proximity alone to convey information.
Toggles can be tricky to test because of the way they can cause configuration to shift. For this reason, it’s generally wise to always test the toggle configuration that you expect to go live with. For example, many teams add a regression test to their test suite where all feature toggles are flipped Off before they’re pushed to production. This prevents surprise regressions if the behavior that was originally deployed with a toggle is later changed. In some cases, it’s also wise to test with all feature toggles flipped On as well.
