Set up feature flags

Sign up for PostHog Cloud (or self-host) and install the posthog-js snippet. Go to Feature Flags and create a boolean flag. In your code, wrap the new feature in if (posthog.isFeatureEnabled('my-flag')). Start with a 0% rollout and increase gradually. PostHog automatically records which flag variant each user received alongside their analytics events.

Create a LaunchDarkly account and project. Install the SDK for your language and initialize it with your SDK key. Create a feature flag in the dashboard and define targeting rules by user attribute (plan, beta tester, internal team). Use the kill switch to instantly disable a feature for all users if an issue is detected in production.

Deploy Unleash via the official Docker image or Unleash Cloud. Create a feature toggle in the admin UI and install the Unleash client SDK in your application. Configure a gradual rollout strategy that starts at 10% of users. The Unleash Proxy can be deployed at the edge to reduce latency for flag evaluation.

Sign up for Flagsmith and create a project with separate development and production environments. Each environment has its own API key so flag states are isolated. Add the flagsmith npm package and call flagsmith.hasFeature('my-flag') in your code. Use the Remote Config feature to store arbitrary string values (API endpoints, copy, thresholds) that you can change without a deployment.