What is a Toggle?

Toggle (also known as a feature flag) is a piece of software functionality that allows developers to turn a specific function on or off. It’s an important tool for many continuous delivery processes, as it allows teams to validate features with a subset of their audience before rolling out the feature to everyone. This reduces the risk that a new release will flop.

Toggles are generally temporary, although they can be used to manage long-lived features. Often times they act as circuit breakers, temporarily disabling non-essential functions during high latency periods, for example. Toggles are also useful for enabling features that would otherwise be too resource intensive for the platform, allowing companies to monetize their product offerings by offering premium features to users.

When designing UIs for toggle switches, it is important to use clear visual feedback to indicate the current state. This can be achieved through color changes, animation, or iconography. It is also important to make the switch easy to interact with and to respond reliably to user input.

It is best practice to name toggles descriptively, and to create a process for managing their lifecycle. Leaving old toggles in the codebase increases management overhead, so it is important to prune them as soon as they are no longer needed. This can be done by adding them to a release backlog or by building a process into your management platform. This helps prevent feature flags from becoming confusing if they are accidentally deployed multiple times or if they are renamed during a migration.