The word toggle derives from an 18th-century definition of “pin passed through the eye of a rope to fasten it.” Today, we use the word in a more figurative sense—to change or flip between different options. In software engineering, toggles are a powerful tool for enabling teams to test new functionality and release it in small increments without impacting existing code or modifying the user experience.
When used with caution, feature toggles can make your website faster and more flexible, while allowing you to test different approaches with minimal risk. However, as with any tool, feature toggles come with a few best practices and risks that you should be aware of before using them on your live site.
One of the most common uses of toggles is to hide content from viewers. You can use toggles to hide article sections, containers, images, maps, key/value items, prompt linked articles, quotes and aloud boxes. When you’re viewing an article in the presentation view, hovering over a toggle-able item will reveal its hidden state. Toggleable items are marked with an eye icon, and you can disable them by clicking the eye again. The toggle feature also works in other areas of the site, including in the navigation menu and search bar.
Feature toggles also offer an effective way to conduct A/B tests with real users. When a toggle is flipped ON, your test participants see the version of your application with the tested feature enabled, and when it’s flipped OFF they see the previous version. This allows your team to test new functionality with actual users and quickly roll back features that don’t perform as expected.
When you’re implementing a toggle system, it’s important to clearly label the settings that each toggle controls. In addition to making it obvious which option the toggle switch controls, you should ensure that your labels describe what state the toggle is in (ON or OFF) and provide any additional context that might be needed. For example, if the toggle is for a specific feature, the label should include the feature name.
Toggle switches are often a good choice for controling settings that have a default value, such as Airplane Mode on a mobile device. Toggles are also preferred over radio buttons for these types of situations because they take up less screen space.
As your feature flag inventory grows, a process for removing old toggles becomes essential. Savvy teams understand that every toggle has a carrying cost and strive to keep the number of idle toggles low. Some teams do this by adding a toggle cleanup task to the team’s backlog, while others build that process into their management platform.
Toggle configuration can be stored in static files or in some type of centralized config store, such as an existing app database. Managing toggle configuration via static files can become cumbersome as your feature flag inventory grows, and ensuring consistent re-configuration across multiple servers can be difficult. In order to address these challenges many organizations move their toggle configuration to a central repository such as a Kameleoon-style config system.
