A toggle (also known as a switch) is a piece of software that lets users easily move between different settings, states, or modes. This feature is particularly useful when a team wants to experiment with a new product design or product behavior but doesn’t want to risk releasing it to all users too early.
The primary benefit of toggles is that they make it easy for users to see and understand what the current state of a feature is at any given time. That’s important because it allows for cognitively acceptable transitions from one state to another without requiring a user to click Save or Submit to trigger a change. However, when toggles are poorly designed they can also create a great deal of confusion for users.
For example, many toggles rely on color to convey state. This can be problematic for users because WCAG recommends that designers don’t rely exclusively on color to communicate meaning. Additionally, choosing the right color for a toggle can be difficult as colors have societal and cultural associations that can vary between populations. Toggle designs should therefore use high contrast visual signifiers, include on/off states in the toggle label (to avoid confusion), and utilize state descriptors to provide additional visibility.
A second drawback of toggles is that they require an application to be restarted to flip a flag’s configuration. This can significantly slow down validation in a production environment and can negatively impact the all-important feedback loop that CI/CD relies on. To address this challenge, savvy teams often implement runtime configuration systems like Split that enable dynamic re-configuration of specific service instances at runtime.