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Best Free and Open Source Feature Flag Tools

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Feature flags are a powerful tool that allows software development teams to deploy features incrementally, test new functionality, and perform A/B testing. With the increasing demand for feature flag management tools (or feature flag tools), developers are looking for reliable, scalable, and efficient solutions. In this article, we will introduce you to some popular open-source feature flag management tools that are actively maintained and offer commercial support.


FeatBit is an open source feature flags management tool (primarily developed using C#) that stands out from the competition with its rich functionality, ease of use, and excellent performance. It is ideal for startups, SMBs, and large enterprises looking for a comprehensive solution to manage their feature flags.

Key advantages of FeatBit include:

  • FeatBit is ideal for self-hosted setups, offering Helm Chart support, Observability with OpenTelemetry, and high availability solution.
  • Rich Integration Capabilities: FeatBit seamlessly integrates with APM tools, data analytics tools, and collaboration platforms.
  • Optimized for Self-Hosted Requirements: FeatBit is designed for self-hosting, supported by Helm Chart, Terraform, and offering high availability and multi-data center solutions.
  • Performance and Scalability: Capable of supporting over 1 million simultaneous online users.
  • Flexible and Straightforward Pricing Model: FeatBit features a simple pricing structure, free from seat-based, environment-based, or API call-based fees.

By using FeatBit, your organization can reduce delivery risks, increase development speed, optimize user experience, innovate your software without bug and impact on buisness.

It's fully open source and licensed under the MIT License.


Flagsmith is an remote configuration and feature flag open source service (primarily developed using Python), making it easy for developers to create, manage, and deploy feature flags across multiple projects, environments, and organizations. It is suitable for teams that require a simple and reliable solution for managing their feature flags.


  • Multiple environment support
  • Remote configuration management
  • API-based access
  • User segmentation
  • Client libraries for various languages

By using Flagsmith, your team can streamline feature rollouts, reduce deployment risks, and improve the overall development process, leading to a strong return on investment. Good support for Python feature toggles.

It's open source and licensed under the BSD-3-Clause license.

You can easily find some articles about flagsmith vs unleash on google.


Unleash feature flags is a widely-used open source feature management platform (primarily developed using Typescript) that provides a comprehensive overview of feature toggles and flags across all your applications and services. It enables software teams worldwide to take full control of how they deploy new functionality to end users. Unleash is suitable for organizations of all sizes looking for a robust feature flag management solution.


  • Flexible architecture
  • Client SDKs for multiple programming languages
  • Built-in activation strategies
  • Web UI for managing feature toggles
  • Role-based access control

Unleash can help your organization mitigate deployment risks, optimize feature rollouts, and increase agility, resulting in a positive return on investment.

It's open source and licensed under the Apache License 2.0.

Go Feature Flag

Go Feature Flag uses Go as its primary development language, and it's a lightweight and fast feature flag service. GoFeatureFlag has a simple and intuitive API that makes it easy to use in any Go project. GoFeatureFlag is a more performant and lightweight solution than LaunchDarkly and ConfigCat. It does not require any external dependencies or services, and can run entirely within your own infrastructure.


  • 100% Opensource, no vendor locking, supports your favorite languages and is pushing for standardisation with the support of OpenFeature.
  • GoFeatureFlag focus is to avoid any complex infrastructure work to use the solution.
  • Cloud ready and can retrieve its configuration from various places, store your data usage where you want and notify you when something changes

It's fully open source and licensed under the Apache License 2.0.

Tools with Primary Focus on Data Analytics


Growthbook is a free, A/B testing and feature flags open source platform designed to help you optimize your user experience and product growth. It is ideal for product teams and marketers seeking a comprehensive solution for A/B testing and feature flag management.


  • A/B testing and experimentation
  • Feature flag management
  • Visual editor for designing experiments
  • Integration with popular analytics platforms

By leveraging Growthbook, your organization can make data-driven decisions, optimize user experiences, and drive product growth, resulting in a substantial return on investment.


PostHog is an open source product analytics platform that offers feature flags, user session recordings, and event-based analytics. It is suitable for organizations that want to gain insights into user behavior, optimize their product, and manage feature releases effectively.


  • Event-based analytics
  • Feature flag management
  • User session recordings
  • Heatmaps and click maps
  • Integration with popular development tools

Implementing PostHog can help your organization improve user experiences, optimize feature releases, and gain valuable insights into user behavior, leading to a significant return on investment.

Principals of choosing a feature flag tool

When integrating a feature flag tool into your development process, several key principles should guide your choice to ensure it meets your team’s needs effectively. Here's an expanded look at each principle:

  1. Choose an Actively Maintained Project: Opt for a project that receives regular updates and active contributions, ensuring its reliability and future viability.

  2. Select a Tool Aligned with Your Team’s Technical Stack: Ensure the tool integrates seamlessly with your existing technology setup, including programming languages and frameworks.

  3. Engage with a Welcoming Community: Participate in a community that values and responds to your feedback and contributions, fostering a collaborative environment.

  4. Prioritize Tools with Comprehensive Documentation: Look for tools that offer clear, detailed, and user-friendly documentation to facilitate ease of use and troubleshooting.

  5. Seek Tools Offering Commercial Support: Consider tools that provide the option of professional support services, useful for addressing complex issues or customization needs.

  6. Ensure High Performance of the Tool: Choose a tool known for its efficiency and robust performance, particularly important for handling high workloads.

  7. Demand Strong Security Features: Security is paramount; opt for tools that offer robust protection measures to safeguard your application and data.

  8. Verify the Tool’s Scalability: The tool should effectively scale with your application’s growth, maintaining performance and reliability.

  9. Focus on Quality Over Popularity: Evaluate tools based on their features and effectiveness rather than solely on their popularity or the number of stars on repositories.

  10. Opt for an Open Source, Self-Hosted Solution: Choose a tool that allows for self-hosting, giving you control over your infrastructure and data.

  11. Be Wary of Outdated or Discontinued Projects: Stay cautious of projects that are no longer updated or maintained, as they can pose security risks and compatibility issues.

  12. Select an open source feature flag management tool with a license that suits your use case and business needs: Licenses such as MIT and Apache 2.0 are often better choices compared to others. For example, the GNU General Public License (GPL) is a copyleft license that requires you to make your source code available to the public if you use the tool in your application. This can be problematic for organizations that want to keep their source code private.


As the need for feature flag management tools continues to grow, it's essential to choose a solution that fits your organization's requirements. FeatBit stands out with its rich feature set, performance, scalability, and customization options, making it an excellent choice for teams looking to adopt feature flags in their development process. Be sure to explore FeatBit and the other open source alternatives mentioned in this article to find the right fit for your team.

You can start testing feature toggles with these free and open source tools. For more open source feature flag tools not mentioned here, you can search on google with the keyword github feature flags.

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