
Hypertune
Type-safe feature flags platform with A/B testing, analytics, and app configuration optimized for TypeScript
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Deliver targeted experiences with feature flags and A/B testing
Flagr is a Go microservice that enables feature flagging, A/B experiments, and dynamic configuration via clear Swagger APIs, with a UI, Docker deployment, and client libraries for multiple languages.

Flagr is a lightweight Go microservice that centralizes feature flag management, A/B experimentation, and dynamic configuration. It exposes a fully documented Swagger REST API, allowing developers to create, update, and evaluate flags programmatically. The built-in UI provides a quick visual interface for flag administration, while client libraries for Go, JavaScript, Python, and Ruby simplify integration across services.
The service can be launched instantly with the official Docker image (ghcr.io/openflagr/flagr) and accessed on port 18000, or tried via the public demo at try-flagr.onrender.com. Its evaluation engine has been benchmarked at sub-millisecond latency under high request rates, making it suitable for real-time decision making in production environments. Because Flagr is self-hosted, teams retain full control over data, scaling, and customization, while the Apache 2.0 license ensures freedom to modify and redistribute the code.
When teams consider Flagr, these hosted platforms usually appear on the same shortlist.
Looking for a hosted option? These are the services engineering teams benchmark against before choosing open source.
Gradual rollout of new UI component
Enable the component for a subset of users, measure conversion, and roll back instantly if needed.
A/B test pricing strategies
Serve different price points to user segments, collect experiment results via API, and decide optimal pricing.
Dynamic configuration of feature toggles per region
Adjust behavior based on entityContext (e.g., state) without redeploying code.
Feature gating for beta testers
Expose experimental features only to identified beta users while keeping them hidden from the general audience.
Official client libraries exist for Go (`goflagr`), JavaScript (`jsflagr`), Python (`pyflagr`), and Ruby (`rbflagr`).
Benchmarks with vegeta show average latency around 370 µs at 2 k requests per second, with 100 % success rate.
Flagr is released under the Apache 2.0 license.
Project at a glance
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