Feature Flags

Unleash is an open-source feature management platform founded in 2014 by Ivar Østhus, then a developer at FINN.no, Norway's largest online marketplace, to enable trunk-based development by protecting features under development.

Reviewed by 7wData

On this page

Publisher review

Unleash is an open-source feature management platform founded in 2014 by Ivar Østhus, then a developer at FINN.no, Norway's largest online marketplace, to enable trunk-based development by protecting features under development. It targets engineering teams at security-conscious organizations, offering self-hosted or cloud deployment with over 10,000 GitHub stars and 20 million downloads. The platform supports boolean and multivariate flag types, percentage-based and targeted rollouts, environment management (dev, staging, production), and a dashboard for managing flags.

It provides 25+ SDKs for major languages and frameworks, zero-latency local evaluation, real-time exposure tracking, health monitoring, automatic rollbacks triggered by metric degradation or custom alerts, and native integrations with CDPs, observability tools, and CI/CD pipelines. Unleash converts any feature flag into an A/B test with one toggle, includes a built-in metrics catalog with statistical significance calculations, and measures feature impact without additional instrumentation. In the competitive landscape, Unleash competes with ConfigCat, DevCycle, Flagsmith, GrowthBook, LaunchDarkly, Statsig, and PostHog.

Its open-source nature and pay-as-you-go pricing differentiate it from LaunchDarkly's proprietary model and PostHog's all-in-one analytics approach. However, Unleash has limitations: basic percentage rollouts and simple targeting rules struggle with complex deployment scenarios, performance bottlenecks occur at scale, usage-based pricing can escalate costs, and it does not offer truly unlimited feature flags. Infrastructure can create latency issues and unexpected bills. Despite these trade-offs, Unleash is rated the 'Easiest Feature Management system to use' by G2 and serves the world's largest, most security-conscious organizations, making it a strong choice for teams prioritizing open-source flexibility and security.

Get the AI & data signal, daily.

48k+ subscribers read this every morning. One email, both newsletters. Unsubscribe anytime.

How it works

  1. Boolean and multivariate flags

    Supports both simple on/off toggles and multivariate flags with multiple variants for complex experimentation.

  2. Percentage-based and targeted rollouts

    Gradually release features to a percentage of users or target specific segments based on custom criteria.

  3. Environment management

    Manage flags across dev, staging, and production environments with separate configurations per environment.

  4. 25+ SDKs for major languages

    Provides SDKs for languages like JavaScript, Python, Java, Go, .NET, and Ruby for easy integration.

  5. Zero-latency local evaluation

    Evaluates flags locally on the client or server, eliminating network round-trips for instant flag checks.

  6. Automatic rollbacks with metric triggers

    Automatically roll back features when metric degradation or custom alerts are detected, reducing manual intervention.

  7. One-click A/B test conversion

    Convert any feature flag into an A/B test with a single toggle, using built-in statistical significance calculations.

Strengths and trade-offs

Strengths

  • Unleash has been downloaded over 20 million times and has over 10,000 GitHub stars, indicating strong community adoption.
  • It offers 25+ SDKs for major languages and frameworks, enabling broad integration across diverse tech stacks.
  • The platform provides zero-latency local evaluation, ensuring flag checks do not introduce network delays.
  • It supports automatic rollbacks triggered by metric degradation or custom alerts, reducing the risk of bad releases.

Trade-offs

  • Basic percentage rollouts and simple targeting rules struggle to handle complex deployment scenarios like multi-variate or gradual ring deployments.
  • Performance bottlenecks at scale can occur, especially when managing thousands of flags across large user bases.
  • Usage-based pricing can escalate costs unexpectedly for teams with high flag evaluation volumes.
  • Infrastructure for self-hosted deployments can create latency issues and unexpected bills due to resource requirements.

Pricing context

Free to self-host under Apache 2 license; Enterprise plans at $75/seat/month for enhanced security, visibility, and control.

Getting started with Feature Flags

  1. Sign up for Unleash

    Go to the Unleash website and create an account for the cloud version, or download the open-source version from GitHub to self-host. Follow the setup instructions to get your instance running.

  2. Connect your application

    Install the appropriate Unleash SDK for your programming language from the list of 25+ supported SDKs. Configure the SDK with your instance's API URL and an API token generated from the Unleash admin dashboard.

  3. Create a feature flag

    In the Unleash dashboard, click 'Add feature toggle' and give it a name. Choose a flag type: boolean for simple on/off or multivariate for multiple variants. Set the initial state to 'off' to protect the feature during development.

  4. Roll out to a percentage

    In the flag's strategy configuration, select 'gradual rollout' and set a percentage, such as 10%. Optionally add targeting rules based on user IDs or custom properties to control which users see the feature.

  5. Monitor and roll back

    Use the dashboard's exposure tracking and health monitoring to observe flag performance. If metrics degrade, enable automatic rollbacks by configuring metric triggers in the flag's settings to revert to 'off' without manual intervention.

Frequently Asked Questions

What is Unleash and how does it work for feature flags?

Unleash is an open-source feature management platform founded in 2014 to enable trunk-based development. It supports boolean and multivariate flags, percentage-based rollouts, and environment management. It offers over 25 SDKs and zero-latency local evaluation for fast flag checks.

What types of feature flags does Unleash support?

Unleash supports boolean flags for simple on/off toggles and multivariate flags with multiple variants for complex experimentation. It also enables percentage-based rollouts to gradually release features and targeted rollouts to specific user segments based on custom criteria.

How much does Unleash cost and what are the pricing plans?

Unleash is free to self-host under the Apache 2 license. Enterprise plans cost $75 per seat per month, offering enhanced security, visibility, and control. Usage-based pricing can escalate costs for teams with high flag evaluation volumes.

What are the main strengths of using Unleash for feature management?

Unleash has over 20 million downloads and 10,000 GitHub stars. It provides 25+ SDKs, zero-latency local evaluation, automatic rollbacks triggered by metric degradation, and one-click A/B test conversion with built-in statistical significance calculations.

What are the limitations of Unleash compared to other feature flag tools?

Unleash's basic percentage rollouts and simple targeting rules struggle with complex deployments like multi-variate or gradual ring rollouts. Performance bottlenecks can occur at scale, and usage-based pricing may lead to unexpected costs.

How does Unleash compare to LaunchDarkly and other competitors?

Unleash is open-source with pay-as-you-go pricing, differentiating it from LaunchDarkly's proprietary model. It competes with ConfigCat, DevCycle, Flagsmith, GrowthBook, Statsig, and PostHog. Unleash is rated the 'Easiest Feature Management system to use' by G2.

Alternatives

How Feature Flags compares

Direct head-to-head against 3 competitors. Picked by 7wData.

This tool

Feature Flags

Pricing
Free to self-host under Apache 2 license; Enterprise plans at $75/seat/month for enhanced security, visibility, and control.
Target
Unleash is an open-source feature management platform founded in 2014 by Ivar Østhus, then a developer at FINN.no, Norway's largest online marketplace, to enable trunk-based
Strength
Unleash has been downloaded over 20 million times and has over 10,000 GitHub stars, indicating strong community adoption.
Watch for
Basic percentage rollouts and simple targeting rules struggle to handle complex deployment scenarios like multi-variate or gradual ring deployments.

ConfigCat

Pricing
Free for 10 flags, $110/mo for 100 flags, $325/mo+ for unlimited
Target
Teams needing simple pricing without per-seat fees
Deployment
Hosted, private cloud, on-prem
Strength
Client-side flag evaluation with zero data collection
Watch for
No built-in experimentation analytics

Unleash

Pricing
Free self-hosted, $75/seat/mo for Enterprise
Target
Open-source adopters with air-gapped needs
Deployment
Self-hosted or SaaS
Strength
Apache 2 license with 25+ SDKs
Watch for
Enterprise pricing requires seat commitments

Flagsmith

Pricing
Open-source core, SaaS plans start at $50/mo
Target
Teams wanting self-hosting flexibility
Deployment
SaaS or full on-prem
Strength
Built-in A/B testing with OpenFeature support
Watch for
Limited analytics in base open-source version

User reviews

No user reviews yet. Be the first to write one.

Sources

Reporting on this tool draws on these publicly available sources.

  1. www.reddit.com
  2. www.reddit.com
  3. www.getunleash.io
  4. www.flagsmith.com
  5. userpilot.medium.com