11 Open-source feature flag tools

Hello and welcome to an overview of 11 open-source feature flag tools. We love feature flags here, and we love open-source! We feel strongly that the more developers can adopt these 2 concepts, the better we are as an industry. We’ve made this handy list of 11 open-source feature flag tools to help you in your feature flag journey.

What is Unleash

Hello, we’re Unleash, and our mission is to make life easier for developers. We’re an open-source Feature Management platform, i.e., we’re a really good way to help you use feature flags. This makes releasing new features less risky, and streamlines the software release process. Unleash can be used as a private hosted cloud instance or as a self-hosted solution, if you prefer that or need Fed Ramp or Air-Gapped use cases. The Unleash repo has over 10,000 GitHub stars and has been downloaded over 20 million times.

Why we made Unleash

In 2014 Ivar was working as a software developer at FINN.no, Norway’s largest online marketplace. Getting new features into production was a pain, so, as a developer, he looked around and wondered if he could write some code to make it easier. The initial goal was to protect features under development, allowing our team to transition to trunk-based development.

10 years later, he’s CTO of Unleash, and we’re the leading open-source feature flag solution. We serve the world’s largest, most security-conscious organizations, and we’re even rated the “Easiest Feature Management system to use” by G2.

Open source feature flag tools

Here’s our list of open source feature flag tools:


It’s us! We obviously think you should choose Unleash, but feature flags make everyone’s software better, and we want to live in a better world.


FeatBit is an open-source feature flag and A/B testing platform. It provides a self-hosted and a cloud solution for managing feature flags and running experiments.


FF4J (Feature Flipping for Java) is an open-source feature flag framework for Java applications and other JVM languages. The framework includes a web console for managing flags and monitoring their status.


Flagsmith is a feature flag and remote configuration service. It offers a platform for managing feature flags, remote config, and A/B testing. 


Flagd is an open-source feature flagging daemon. Flagd can be run as a sidecar container in Kubernetes or as a standalone service.


Flagr is a feature flagging, A/B testing and dynamic configuration microservice written in Go. It was originally developed by Checkr and then open-sourced later.


Flipper is an open-source tool for managing feature flags in Ruby applications. Flipper supports integration with different data stores like Redis and ActiveRecord. It’s commonly used in Rails projects.



Flipt is an open-source feature flag management solution. Its cloud offering is currently under development.


Go Feature Flag

GO Feature Flag is an open-source, feature flag management solution written in Go (obviously). GO Feature Flag supports gradual rollouts, user targeting, and A/B testing.



GrowthBook is an open-source feature flagging and experimentation platform.


PostHog is an open-source product analytics and experimentation platform. It includes a feature flag service.


Thank you for reading.

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