We've built an open-source feature flag server for 11 years

Unleash is an open-source feature management platform that lets software teams decide when and for whom new functionality is activated, without needing to redeploy applications. Its central argument is that feature flags make releases smaller and safer: teams can work on several features at once, test changes against production traffic, gradually expose functionality, and quickly disable a feature if it causes problems. Flags can support targeted releases, canary rollouts, kill switches, and A/B tests. Unleash provides a central view of flags across applications and environments, with activation strategies, tagging, integrations, audit logs, and insights for identifying stale flags and technical debt. Its API-first design allows automation, while client SDKs connect applications across many languages and frameworks.

The software can be run locally with Docker or as a Node.js application, and organizations can self-host it or use a hosted service. The open-source edition includes core flag management and two environments; paid Pro and Enterprise plans add capabilities such as role-based access, single sign-on, additional environments, advanced segmentation, and more security and hosting options. Unleash emphasizes privacy by keeping end-user data within the application, and offers Unleash Edge to scale delivery to frontend clients without overloading the main server. The project has been maintained for 11 years and presents itself as a community-built tool, with public contribution pathways, documentation, support channels, and a live demo for evaluation.