Flagsmith

Flagsmith is an open-source feature flag and remote configuration platform that enables development teams to deploy code more frequently and safely by decoupling feature releases from code deployments. Founded by Ben Rometsch and the Flagsmith team, the platform allows developers to toggle features on or off at runtime, segment users for gradual rollouts, and conduct A/B testing experiments without requiring code changes or redeployments. Unlike managed SaaS-only solutions like LaunchDarkly, Flagsmith is fully open-source under the BSD-3-Clause license, giving teams the option to self-host the entire platform on their own infrastructure for maximum data privacy and control, or use the managed Flagsmith Cloud service for convenience. Core capabilities include: boolean feature toggles for simple on/off switches, multivariate flags for supporting multiple values (strings, numbers, booleans, JSON) per flag, percentage-based gradual rollouts for canary deployments, user segment targeting based on custom traits and properties (e.g., email domain, subscription tier, geographic region), environment management (Development, Staging, Production) with separate flag configurations per environment, scheduled flag updates for time-based releases, audit logs for compliance tracking, role-based access control (RBAC) for team management, and a comprehensive REST API and SDKs for over 14 programming languages and platforms (including JavaScript, Python, Go, Java, .NET, React, React Native, Flutter, Android, iOS, and more). The platform integrates with analytics tools like Amplitude and Segment for measuring experiment impact. As of 2026, Flagsmith has over 5,000 GitHub stars.