Unleash

Unleash is a feature flag platform that handles gradual rollouts, user targeting, and instant kill switches without redeploying. Think of feature flags as on/off switches for your code that you can flip without shipping new code.

TypeScript, Apache 2.0. Supports gradual rollouts, A/B testing, user segmentation, and environment-specific flags (enable in staging but not production). SDKs for every major language. Self-hosted Open Source is free with no user or flag limits. Docker Compose gets you running in minutes. The free version includes everything a small team needs: flags, strategies, environments, API access, and the admin UI.

Pro plan: $80/mo for 5 team members, adds change requests (approval workflows), banners, custom event tracking. Enterprise is custom with SAML SSO, SCIM, audit logs, and service accounts. Solo: self-host free, it's trivial to run. Small teams (2-10): self-host free unless you need approval workflows. Medium teams: Pro at $80/mo or self-host with custom RBAC. Large teams: Enterprise for SSO and compliance, or evaluate LaunchDarkly if you want managed.

The catch: the open source version doesn't have change requests (peer review before toggling flags in production). For regulated environments where you need an audit trail of who changed what and who approved it, that's a paid feature. And the market leader LaunchDarkly has a richer integration ecosystem.