Toggle is a simple but powerful tool for increasing the speed and precision of your application’s testing and deployment processes. Savvy teams use feature toggles in many different ways to reduce the risk that a new product release will fail or cause unintended side effects.

A toggle is a switch with two positions, on and off. Toggle switches are found in many devices and software applications, including laptops, smartphones, tablets, video chat apps and games.

In software development a toggle can be used to enable or disable features that can impact performance or user experience (UX). Toggle switches are especially useful for creating responsive designs in web and mobile applications where the layout can adapt to various screen sizes.

Feature toggles are an important part of the agile development process as they allow your team to deploy features while they are still in progress. This supports agile approaches to development and avoids the need to maintain code branches as you would in more traditional waterfall-based development models.

The most common use of feature toggles is for experimentation and validation with a selected segment of your user base. You turn a new feature on for a group of users and then use analytics to monitor performance, catch bugs and assess how well the feature is received.

Operation toggles are generally short-lived — once a feature is rolled out and has been running for a few weeks without issues your team can retire the toggle. Permission toggles can be more long-lived, as they are typically a way to control how a feature is enabled for a particular user cohort. Managing toggle configuration via static files becomes cumbersome when you reach a certain scale so many teams move their feature flags into some kind of centralized store like an existing application DB.