A toggle is a switch that allows you to select one of two different states or options. You can use it in technology, computing, programming and communications to toggle between a variety of settings and modes.

In software development, toggles are a mechanism that allows developers to deploy features to users with predefined states. This allows software teams to test and refine new user features without affecting existing functionality or interrupting production deployment cycles. In other words, it is a way to do “agile testing” without changing the codebase, which can be difficult under more traditional waterfall development methodologies.

You can also use toggles to perform multivariate or A/B testing. By defining an experiment as a toggle you can consistently send each user down one codepath or the other, and then analyze the results of that experience to make data-driven optimizations.

Toggles are very useful in responsive designs, as they allow you to hide or show UI elements based on screen size and device type. However, if you’re designing for accessibility, you need to be careful with which toggles you use — they can be confusing for users with low vision and cognitive impairments. For example, some toggles use color to indicate their state (on/off), but WCAG guidelines say not to rely on colors alone for accessibility.

The best practice is to name each toggle clearly and explicitly. This is especially important if you’re using toggles in a larger codebase, because it can help you track changes to the configuration and understand where any bugs might be originating.

Another common practice is to put toggles in a dedicated feature branch, so they can be hidden until they’re ready for release. This approach supports agile development processes and allows your team to continue to deliver software while they’re writing new features. It can also help you avoid the delays that might be introduced by a lengthy testing and QA process that’s typically required under more traditional waterfall development models.

While it might be tempting to use a toggle for every single setting in your application, that can quickly become overwhelming for both your codebase and your customers. Instead, you should only use toggles to support the most critical functions in your product, and be sure to test and QA each toggle before making it available to users.

You can manage toggle configuration through a number of different means, ranging from static files which are less dynamic to more sophisticated approaches which require the deployment of a separate application DB. Whichever you choose, you should make this management as easy and intuitive as possible so that both developers and system operators can maintain consistency across a fleet of servers.

If you’re implementing toggles for the first time, you might want to consider using a “release” toggle to manage your changelog. This is a special toggle that’s rolled out to a small cohort of users on each release, and it’s an ideal way to manage new releases while keeping the rest of your product stable and consistent.