What is Flagr used for?

Flagr is a Go microservice for feature flags, A/B testing, and dynamic configuration, with an evaluation API, a Vue 3 UI, and several storage backends. It is a good fit for gradual rollouts of new features and running experiments without redeploying.

Is Flagr open source?

Yes. Flagr is open source under the Apache-2.0 licence. Its source code is on GitHub at openflagr/flagr and is written mainly in Go.

Yes. Flagr is open source, so the software itself is free to use.

Can I self-host Flagr?

Yes. Flagr can be self-hosted on your own server or infrastructure; there is no official hosted version.

What is Flagr an alternative to?

Flagr is an open-source alternative to Split, Statsig, ConfigCat and LaunchDarkly. Other open-source alternatives to Split include Flagsmith, FeatureProbe and GrowthBook.

Is Flagr actively maintained?

Yes. The most recent commit to Flagr was on 27 September 2026, and the latest release is 1.2.4, published on 20 August 2026. The project has 2.6k stars on GitHub.

Flagr: open-source alternative to Split, Statsig, ConfigCat

About Flagr

Flagr is an open-source Go service for feature flags, A/B tests, and dynamic configuration. Your application calls an evaluation endpoint with the identity and context of the entity being evaluated, and Flagr returns a variant and an optional JSON attachment. This lets teams ship code turned off, enable it for specific audiences, run experiments with sticky assignment, and change runtime configuration without redeploying.

It is self-hosted and can store data in SQLite, MySQL, PostgreSQL, or JSON files managed through GitOps, and it provides a Vue 3 interface and an official Docker image. The project continues the development of the original checkr/flagr repository and is released under the Apache-2.0 license. Published load tests show it handling thousands of requests per second with sub-millisecond median latency.

A hosted demo is available for trying the UI, and the documentation covers integration, self-hosting, environment variables, and the API reference. Flagr suits engineering teams that want a lightweight, self-run alternative to commercial feature management platforms.

Key features

Feature flags with per-audience targeting
A/B testing with sticky variant assignment
Dynamic configuration via JSON attachments
Evaluation API for applications
SQLite, MySQL, PostgreSQL, or JSON storage
Vue 3 admin UI and Docker image

Good fit for

→Gradual rollouts of new features
→Running experiments without redeploying

Built with: Go
Tags: feature-flags; ab-testing; dynamic-configuration; go; microservice; experimentation; self-hosted; docker

Flagr: questions and answers

What is Flagr used for?: Flagr is a Go microservice for feature flags, A/B testing, and dynamic configuration, with an evaluation API, a Vue 3 UI, and several storage backends. It is a good fit for gradual rollouts of new features and running experiments without redeploying.
Is Flagr open source?: Yes. Flagr is open source under the Apache-2.0 licence. Its source code is on GitHub at openflagr/flagr and is written mainly in Go.
Is Flagr free?: Yes. Flagr is open source, so the software itself is free to use.
Can I self-host Flagr?: Yes. Flagr can be self-hosted on your own server or infrastructure; there is no official hosted version.
What is Flagr an alternative to?: Flagr is an open-source alternative to Split, Statsig, ConfigCat and LaunchDarkly. Other open-source alternatives to Split include Flagsmith, FeatureProbe and GrowthBook.
Is Flagr actively maintained?: Yes. The most recent commit to Flagr was on 27 September 2026, and the latest release is 1.2.4, published on 20 August 2026. The project has 2.6k stars on GitHub.