What Are the Best Open Source Feature Flags Tools Available in 2023?

Introduction

Feature flags have become a vital aspect of modern software development. They enable developers to manage and control the deployment of new features with ease and flexibility. The landscape of open source feature flag tools in 2023 is diverse, with numerous options each offering unique features and benefits. In this comprehensive guide, we'll explore the best open source feature flag tools available, distinguishing between dedicated feature flagging tools and those primarily focused on data analytics.

Tools Mentioned in this Article:

FeatBit, Flagsmith, Unleash, GoFeatureFlag, FlagR, Flipper, Flipt, FeatureHub, PostHog, Growthbook

Top Open Source Feature Flag Tools

FeatBit

FeatBit is an open-source feature flag management service. It allows software teams to control and manage new features in their applications easily. With FeatBit, developers can deploy code safely, test new functionalities, and manage feature rollouts across different environments, including web, mobile, and server-side applications. FeatBit is designed for self-hosting, catering to organizations that prefer managing their feature flagging solutions in-house. It is an ideal choice for companies that prioritize control over their data and infrastructure, offering deployment options on-premises or in private cloud environments.

Key Features of FeatBit:

• Ideal for Self-Hosted Requirements: FeatBit supports deployments through Helm Chart and Terraform, along with OpenTelemetry support for Observability. It provides high availability and multi-data center solutions, catering to complex hosting needs.
• Performance and Scalability: Designed for speed and scalability, the platform effortlessly supports over 1 million simultaneous online users, demonstrating its capability to handle large-scale operations.
• Rich Integration Capabilities: FeatBit features extensive webhook integration, seamlessly connecting with various Application Performance Management (APM) tools, team collaboration tools, and other third-party services with REST APIs. Additionally, it offers a Data Export feature for exporting feature flag evaluations and metric event data to third-party data warehouses and analytics tools.
• Flexible and Straightforward Pricing Model: FeatBit employs a clear pricing model, free from seat-based, environment-based, or API call-based fees. This approach enhances transparency and predictability for businesses, simplifying budget planning.

Technical Stack: .NET (C#)

License: MIT

FeatBit on GitHub: https://github.com/featbit/featbit

Flagsmith

Flagsmith is an open-source feature flag and remote configuration service that offers flexibility in deploying to various environments. It allows users to choose between using a hosted API, deploying to a private cloud, or running on-premise. Flagsmith simplifies the process of creating and managing feature flags across different platforms, including web, mobile, and server-side applications. By wrapping sections of code with flags, developers can easily manage these features, tailoring their application's behavior based on different environments, user segments, or other conditions​​.

Key Features of Flagsmith:

• Cross-Platform Configuration: Flagsmith's flags can be set up for remote configuration across different platforms, allowing real-time alterations without waiting for app store approvals.
• Flagsmith offers robust integrations with various platforms, enhancing its utility and versatility. This includes integration with CI/CD platforms like Terraform, analytics platforms such as Amplitude, Heap Analytics, Mixpanel, Segment, and Rudderstack, and the ability to integrate with custom analytics platforms or data warehouses.
• Broad SDK Compatibility:
  • Client-Side: Supports JavaScript, React Native, React, Android, iOS, Next.js.
  • Server-Side: Works with Node.js, Python, PHP, Ruby, Go, .NET, Ruby, Rust, Elixir.
• Flexible Pricing: Flagsmith is free for up to 50,000 requests monthly on the cloud service. Beyond this, self-hosted and private cloud options are available for larger needs.

Technical Stack: Python

License: BSD 3-clause

Flagsmith on GitHub: https://github.com/flagsmith/flagsmith

Unleash

Unleash stands out as a prominent open-source feature flag service, backed by a robust community and a clear development roadmap. It's an extensively used platform, primarily developed in TypeScript, which offers a detailed view of feature toggles and flags across various applications and services. This platform empowers software teams globally to control the deployment of new features effectively. Unleash stands out as the most popular open-source solution for feature flagging on GitHub and is compatible with various languages and frameworks, offering support for 10+ official client and server SDKs and over 5 community SDKs.

Key Features of Unleash:

• Enterprise-Level Security and Scalability: Designed with enterprise security and privacy in mind, Unleash can be run in a private data center or hosted as a single-tenant SaaS offering. This flexibility caters to organizations with strict security and privacy requirements.
• Extensive SDK Support: Unleash provides official SDKs for major frameworks and programming languages. Additionally, the community has contributed SDKs for other, less common frameworks, enhancing its versatility. Wide Array of Supported SDKs:
  • Client-Side: Includes JavaScript, Android, Flutter, iOS, React, Svelte, Vue.
  • Server-Side: Encompasses Go, Java, Node.js, PHP, Python, Ruby, Rust, .NET.
  • Community Maintained: Covers Angular, Clojure, C++, ColdBox, Dart, Elixir, Haskell, Laravel, NestJS, React Native, Solid.
• Cost-Effective Solution: Unleash offers a free version for self-hosting up to two environments. For more advanced features like segmentation or custom activation strategies, a paid managed version (SaaS) is also available.

Technical Stack: TypeScript

License: Apache

Unleash on GitHub: https://github.com/unleash/unleash

GoFeatureFlag

GoFeatureFlag is an open-source solution that provides a streamlined and comprehensive approach to feature flag implementation. This tool is designed to simplify the use of feature flags in your code without the need for vendor involvement. It was initially created for the Go programming language but has since expanded to support multiple languages through the OpenFeature project. This expansion is facilitated by a simple API server called the relay proxy, which can be hosted to accommodate various languages.

Key Features of GoFeatureFlag:

• Lightweight and Open Source: GoFeatureFlag is known for its simplicity and lightweight nature, making it an easy-to-implement solution for feature flagging​​​​.
• Multi-Language Support: While originally designed for Go, GoFeatureFlag now supports multiple languages due to the standardization efforts of the OpenFeature project. This makes it a versatile tool for diverse development environments​​.
• Flexible Configuration Storage: The tool allows storing configuration flags in various locations, including HTTP, S3, and Kubernetes, providing flexibility in configuration management

Technical Stack: Go

License: MIT

GoFeatureFlag on GitHub: https://github.com/thomaspoignant/go-feature-flag

FlagR

FlagR is a dynamic microservice designed for feature flagging, A/B testing, and dynamic configuration. It is an open-source Go service that focuses on delivering tailored experiences to users and entities, while also monitoring the impact of these changes. FlagR provides a suite of tools for managing feature flags and conducting experimentation, complete with clear Swagger REST APIs for easy management and evaluation of flags.

Key Features of FlagR:

• FlagR offers robust functionality for feature flagging and A/B testing. This allows teams to conduct controlled rollouts of new features, test different variations, and make data-driven decisions about product enhancements​​.
• Dynamic Configuration: The service allows for dynamic configuration, meaning adjustments can be made on-the-fly without the need for redeploying applications. This flexibility is key for rapidly responding to user feedback or changing market conditions​​.

Technical Stack: Go

License: MIT

FlagR on GitHub: https://github.com/openflagr/flagr

Flipper

Flipper is an open-source library specifically designed to offer feature flags for Ruby and Rails. It is known for its simplicity, aesthetic appeal, and high performance. Flipper Cloud, an extension of Flipper, provides a comprehensive platform built on the core Flipper library. This platform simplifies the management of feature flags across various projects and environments, making it an ideal tool for organizations that wish to centralize control, access, and auditing of feature flags.

Key Features of Flipper:

Flipper Cloud allows for the centralized management of all projects. This centralization eliminates the need for setting up feature flags in disparate ways across different applications or micro-services. It streamlines control, access, and auditing processes for the entire organization, ensuring consistency and efficiency​.

Technical Stack: Ruby

License: MIT

Flipper on GitHub: https://github.com/flippercloud/flipper

Flipt

Flipt is a feature management solution that is enterprise-ready, powered by GRPC, and GitOps-enabled. It's designed to adhere to DevOps best practices by separating releases from deployments, and it is built with high-performance engineering organizations in mind. Flipt can be seamlessly integrated into existing infrastructures, ensuring that sensitive information is not sent to third parties and reducing the latency often associated with internet communication.

Key Features of Flipt:

• Flipt is tailored to integrate with DevOps and GitOps workflows, allowing for continuous configuration and deployment. This integration supports trunk-based development workflows and facilitates testing new features internally during development before full production release. It also includes functionality for emergency kill switches to ensure system safety and feature gating for different permission levels.
• Flipt is designed for speed, co-locating with existing services to minimize latency and accelerate application performance. Its design is simple, being a single binary with no external dependencies by default, which simplifies installation and maintenance.

Technical Stack: Go

License: GPL-3.0

Flipper on GitHub: https://github.com/flipt-io/flipt

FeatureHub

FeatureHub is a Cloud Native platform designed to assist software teams in managing their features, encompassing everything from feature flags (also known as feature toggles) to A/B experiments and remote or centralized configuration. It serves as a critical tool for enabling feedback loops, feature testing, and experimentation in production environments with real users. FeatureHub offers both a self-hosted platform and a cloud-hosted SaaS solution, adaptable for use in various organizational contexts, from small startups to large enterprises with numerous applications and teams.

Key Features of FeatureHub:

FeatureHub can be run on your own infrastructure as a self-hosted platform, providing control and customization to fit specific organizational needs. Additionally, it offers a cloud-hosted SaaS solution with simple pay-as-you-go pricing, which includes a 30-day free trial. This flexibility makes it accessible for a wide range of company sizes and types​​.

Technical Stack: Dart

License: Apache 2.0

FeatureHub on GitHub: https://github.com/featurehub-io/featurehub

Tools with Primary Focus on Data Analytics

While the following tools offer feature flagging capabilities, their primary focus is on data analytics and A/B testing. These tools should be considered when feature flagging is part of a broader data analytics and experimentation strategy.

PostHog

PostHog is a popular alternative to analytics tools like Amplitude. It's an all-in-one platform, which means it offers product analytics, session replay, A/B testing, and user surveys, in addition to feature flags. PostHog's feature flags enable conditional rollouts, multivariate flags, JSON payloads, automated usage reports, local evaluation, and more. They power its A/B testing features, so you can test product changes for their impact on key metrics. PostHog also offers an early access feature management feature, which enables users to self-onboard to beta features behind feature flags.

Technical Stack: Javascript

License: MIT

PostHog on GitHub: https://github.com/posthog/posthog

Growthbook

GrowthBook is an open-source platform designed for feature flagging and A/B testing. It caters to the needs of data teams, engineers, and product managers, offering a versatile and customizable tool for both analyzing experiment results and facilitating code deployment. The platform is developed with the aim of empowering teams with a powerful in-house tool without the need for extensive internal tool development. It is engineered to work seamlessly with existing data and metrics, ensuring data transparency and high performance.

Technical Stack: Javascript

License: MIT

Growthbook on GitHub: https://github.com/growthbook/growthbook

Key Principles of Choosing an Open Source Feature Flags Management Tool

When choosing a feature flag tool, it's essential to consider the following factors:

Active Maintenance

• Importance: Regular updates and active maintenance indicate the tool's reliability and the developers' commitment to improving it.
• Checklist: Look for recent commits, resolved issues, and ongoing discussions in the project's repository.

Technical Stack Alignment

• Importance: The tool should seamlessly integrate with your current technology stack to avoid compatibility issues.
• Checklist: Ensure the tool supports your programming languages and frameworks, and check for available SDKs or APIs.

Community Involvement

• Importance: A vibrant community contributes to the tool's robustness and offers a platform for getting help and sharing knowledge.
• Checklist: Look for active forums, user groups, or chat channels, and note how responsive the community is to questions and feedback.

Quality Documentation

• Importance: Comprehensive documentation is vital for ease of installation, troubleshooting, and effective use of the tool.
• Checklist: Seek out detailed guides, API documentation, FAQs, and real-world examples or case studies.

Commercial Support

• Importance: Access to professional support can be crucial for troubleshooting complex issues or customizing the tool for specific needs.
• Checklist: Check if the open source tool offers a paid version with dedicated support or if there are third-party vendors providing support services.

Performance Efficiency

• Importance: A tool that performs well under load is crucial, especially for high-traffic applications.
• Checklist: Look for performance benchmarks, case studies, and user testimonials regarding the tool’s efficiency.

Robust Security

• Importance: Security is non-negotiable, as feature flags can affect application behavior and user data.
• Checklist: Evaluate the tool's security features, such as encryption, access control, and compliance with security standards.

Scalability

• Importance: The tool should be able to scale with your application as it grows.
• Checklist: Look for information on how the tool handles increased loads, and check if it has been used in large-scale environments.

Focus on Quality, Not Just Popularity

• Importance: High star counts on repositories don't always equate to high quality; thorough evaluation is key.
• Checklist: Assess the tool based on its features, performance, community support, and alignment with your needs rather than its popularity alone.

Self-Hosted Open Source Solution

• Importance: A self-hosted solutions (like Helm Chart, Terraform) gives you control over your data and infrastructure.
• Checklist: Ensure the tool can be deployed on your own servers or private cloud and check for any dependencies or infrastructure requirements.

Beware of Outdated or Discontinued Projects

• Importance: Using outdated tools can pose security risks and compatibility issues.
• Checklist: Verify the last update date, check the release history, and look out for any announcements regarding the project's status.

Be Cautious of Open Source Licenses

It's important to 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.

Feature Comparison

Open source feature flag management tools are often referred to as alternatives to LaunchDarkly. When evaluating the features of each tool, I prefer using LaunchDarkly's feature list as a benchmark. This comparison is detailed in my other article, 'What Are the Viable Alternatives to LaunchDarkly for Feature Flagging?' I recommend reading this article for further insights.

Conclusion

The landscape of open source feature flags tools in 2023 offers a rich array of options, each catering to different technical needs and organizational scales. From Unleash's comprehensive feature toggle management to the minimalistic approach of GoFeatureFlag, there's a tool for every scenario. It's essential to choose a tool that aligns with your team's technical stack, size, and specific requirements.

Additionally, for teams focusing on data analytics and experimentation, tools such as Growthbook and PostHog offer integrated feature flagging solutions. Combining pure feature flagging tools with data analytics tools is also a popular approach to harness the strengths of both.

By carefully selecting the right tool, organizations can effectively manage feature rollouts, enhance their software development processes, and make data-driven decisions.

Related articles

Best Free and Open Source Feature Flag Tools

What Are the Viable Alternatives to LaunchDarkly for Feature Flagging?