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GO Feature Flag documentation

GO Feature Flag is a lightweight, open-source feature flag solution with no backend to run.

You describe your flags in a simple configuration file, serve them with a single stateless service — the relay proxy — and evaluate them from your applications in 16 languages through OpenFeature, the CNCF standard for feature flagging.

No database, no proprietary SDK, no vendor lock-in.

New to feature flags?

Read What are feature flags? for a quick primer, or Why GO Feature Flag? to see how it compares to other solutions.

Start here​

Get started in 5 minutes

Create your first flag, start the relay proxy, and evaluate the flag from your application.

Get started

Pick your SDK

16 languages, client-side and server-side, all built on the OpenFeature standard.

Get started

How it works​

1. Describe your flags in a configuration file. Variations are the possible values, and the rules decide who gets which one.

flags.goff.yaml
show-email-contact:
  variations:
    enabled: true
    disabled: false
  targeting:
    - query: company eq "monsters-inc"
      variation: enabled
  defaultRule:
    variation: disabled

2. Evaluate the flag in your application through the OpenFeature SDK. You always get a value back — the default one if anything goes wrong.

evalCtx := of.NewEvaluationContext("user-123", map[string]any{"company": "monsters-inc"})
showContact := client.Boolean(ctx, "show-email-contact", false, evalCtx)

Change the configuration file and the new behaviour is live, without redeploying or restarting your application.

info

The snippet above is in Go, but the API is the same in every language. Check the SDKs section for the one matching yours.

Explore the documentation​

Concepts

Architecture, flag evaluation, evaluation context, flag sets and the SDK paradigms.

Configure your flags

The flag format, targeting rules and custom bucketing to decide who gets what.

Rollout strategies

Progressive rollouts, scheduled changes, A/B testing and percentage-based releases.

Relay proxy

Configure, deploy and monitor the only component you run in your infrastructure.

SDKs

OpenFeature providers for 16 languages, plus the OFREP standard protocol.

Store your configuration

Keep your flags where it suits you: S3, GitHub, Kubernetes, MongoDB, PostgreSQL, Redis and more.

Export evaluation data

Send every flag evaluation to Kafka, BigQuery, S3, OpenTelemetry, a webhook and more.

Notify flag changes

Get alerted in Slack, Discord, Microsoft Teams or your own webhook when a flag changes.

Tracking

Track how your flags are used and measure the impact of your experiments.

Tools

CLI, linter, editor autocomplete and AI tooling to work with your flag configuration.

Contributing

GO Feature Flag is open source and community driven, here is how to help.

Writing a Go service and prefer not to run the relay proxy? GO Feature Flag is also available as a Go module you can embed directly into your application.

Need help?​