Feature Flags

Feature flags (feature toggles) enable you to deploy code but control when and to whom features are released.

What are Feature Flags?

A feature flag is a conditional statement that controls whether code is executed or not.

if (featureFlag.isEnabled('new-checkout')) {
  return <NewCheckout />
} else {
  return <OldCheckout />
}

Types of Feature Flags

• Release flags: Control feature rollout
• Experiment flags: A/B testing
• Ops flags: Circuit breakers, kill switches
• Permission flags: User-based access

Basic Implementation

interface FeatureFlag {
  name: string
  enabled: boolean
  rollout?: number // 0-100%
  users?: string[]
}

Tools

• LaunchDarkly
• Split.io
• Flagsmith
• Unleash
• PostHog