featureflagging

Feature flagging, or feature toggling, is a software development technique that wraps new or risky functionality in a runtime switch. A feature flag in code can be turned on or off without redeploying. Flag values are stored in a configuration store or managed by a feature flag service, and a client library evaluates the flag to choose the code path. Flags may be boolean or multivariate and can be scoped by user, group, environment, or experiment context.

Common use cases include safer releases and rapid rollback, dark launches, canary deployments, blue-green deployments, and A/B testing. Teams gradually expose features to subsets of users to validate behavior or compare variants. The technique enables releasing software independently from code changes, reducing downtime and enabling faster iteration.

Benefits include reduced release risk, greater deployment flexibility, support for continuous delivery, and the ability to run experiments. Risks include flag debt from accumulating toggles, performance overhead, operational complexity, and potential security or data governance concerns if flags expose sensitive logic. Proper lifecycle management is required to avoid leaving stale flags in production.

Best practices include treating flags as temporary artifacts with defined owners and expiration dates, using clear naming, documenting purpose, and planning retirement of flags. Centralized flag management reduces drift and enables auditability. Integrate flag evaluation with CI/CD and observability to monitor impact. Tools range from open-source libraries to commercial services and usually provide dashboards, access controls, and multi-environment support.