A toggle is a physical switch, often used to turn something on or off. In software development a toggle is a control which can be flipped between two states. Toggles are commonly used in web and app design to provide a clearer, more intuitive way for users to update preferences, settings or other kinds of information.
Toggles are also a key component in many data-driven optimization techniques such as multivariate or A/B testing and to enable features to be “flipped on” for specific cohorts of users at runtime. This approach allows developers to compare the performance of different codepaths, for example the ecommerce purchase flow for an ecommerce site or the Call To Action wording on a button.
A feature toggle is a key tool in any developer’s arsenal but it’s important to use them sparingly and thoughtfully. They can have a huge impact on user experience and it’s important to make sure you’re using them only when they truly add value. When you do deploy a toggle make sure it’s properly configured, easy to find and manage. And don’t let idle toggles hang around in your code – be sure to prune them as soon as their lifecycle has run out.
A common method for managing toggle configuration is via static files but this can be problematic once you start to scale up. Modifying these files can be tricky and it’s difficult to ensure consistency across a fleet of servers. For this reason many organizations move to a centralized toggle configuration system such as an existing application DB or a dedicated feature flag management system.