Implement feature flags (toggles) for controlled feature rollouts, A/B testing, canary deployments, and kill switches. Use when deploying new features gradually, testing in production, or managing feature lifecycles.

Feature Flag System Table of Contents [Overview]( overview) [When to Use]( when to use) [Quick Start]( quick start) [Reference Guides]( reference guides) [Best Practices]( best practices) Overview Implement feature flags to decouple deployment from release, enable gradual rollouts, A/B testing, and provide emergency kill switches. When to Use Gradual feature rollouts A/B testing and experiments Canary deployments Beta features for specific users Emergency kill switches Trunk based development Dark launching Operational flags (maintenance mode) User specific features Quick Start Minimal working example: Reference Guides Detailed implementations in the references/ directory: Guide Contents [Feature Flag Service (TypeScript)](references/feature flag service typescript.md) Feature Flag Service (TypeScript) [React Hook for Feature Flags](references/react hook for feature flags.md) React Hook for Feature Flags [Feature Flag with Analytics](references/feature flag with analytics.md) Feature Flag with Analytics [LaunchDarkly Style SDK](references/launchdarkly style sdk.md) LaunchDarkly Style SDK [Admin UI for Feature Flags](references/admin ui for feature flags.md) Admin UI for Feature Flags Best Practices ✅ DO Use descriptive flag names Document flag purpose and lifecycle Implement gradual rollouts Track flag evaluations Clean up old flags regularly Use feature flags for experiments Implement kill switches for critical features Test both enabled and disabled states Use consistent hashing for stable rollouts Provide admin UI for non technical users ❌ DON'T Use flags for permanent configuration Accumulate technical debt with old flags Skip flag cleanup Make flags too granular Hard code flag checks everywhere Skip analytics and monitoring

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