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Flagger

flagger.app

Free plan Self-hosted
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Spec score 8.2 #11 of 29 in Progressive Delivery Software

What it is

Flagger is a self-hosted Kubernetes operator that automates progressive delivery for applications running on Kubernetes. It gradually shifts traffic to a new version while checking measures such as HTTP or gRPC request success and latency. Deployment approaches include canary releases, A/B testing, and blue/green deployments, routed through an ingress controller or a service mesh compatible with the Kubernetes Gateway API. Built-in checks cover HTTP request success rate and duration; teams can add custom metrics and webhooks for acceptance tests, load tests, or other validation. Release analysis can query systems including Prometheus, Datadog, CloudWatch, New Relic, Graphite, Dynatrace, InfluxDB, and Google Cloud Monitoring. If SLO analysis detects a performance drop, Flagger rolls back the release automatically. Manual controls allow approval, pausing, or resuming deployments, and notifications can go to Slack, Microsoft Teams, Discord, or Rocket. It is configured through Kubernetes custom resources, works with Kubernetes-compatible CI/CD solutions, and can be used with Flux for GitOps canary pipelines. Flagger is Apache 2.0 licensed and free.

Spec sheet

Purpose
Flagger automates progressive delivery for applications running on Kubernetes by shifting traffic gradually while measuring metrics and running conformance tests.Read 8 Oct 2026 · docs.flagger.app
Product
Flagger is a progressive delivery Kubernetes operator that automates application releases on Kubernetes.Read 8 Oct 2026 · flagger.app
Support
The project directs users to its documentation, the CNCF community Slack #flagger channel, Flux talks, and GitHub issues for help.Read 8 Oct 2026 · flagger.app
License
Flagger is licensed under Apache 2.0.Read 8 Oct 2026 · flagger.app
Founded
2018Read 23 Sep 2026 · flagger.app
Built-in metrics
The built-in checks are HTTP request success rate and request duration.Read 8 Oct 2026 · docs.flagger.app
Compatibility
Flagger is configured with Kubernetes custom resources and is compatible with CI/CD solutions made for Kubernetes.Read 8 Oct 2026 · docs.flagger.app
Configuration
Flagger is configured using Kubernetes custom resources and works with CI/CD solutions made for Kubernetes.Read 8 Oct 2026 · docs.flagger.app
Deployment strategies
It supports canary releases, A/B testing, and blue/green deployments.Read 8 Oct 2026 · docs.flagger.app
GitOps
Flagger can be used in GitOps pipelines with tools such as Flux CD.Read 8 Oct 2026 · docs.flagger.app
History
Flagger was initially developed in 2018 at Weaveworks by Stefan Prodan and became a CNCF project in 2020.Read 8 Oct 2026 · flagger.app
Manual controls
The feature matrix lists manual gating to approve, pause, or resume deployments across supported routing integrations.Read 8 Oct 2026 · github.com
Metrics
Release analysis can query Prometheus, InfluxDB, Datadog, New Relic, CloudWatch, Stackdriver, or Graphite.Read 8 Oct 2026 · docs.flagger.app
Metrics integrations
Metric query integrations listed include Prometheus, Datadog, CloudWatch, New Relic, Graphite, Dynatrace, InfluxDB, and Google Cloud Monitoring.Read 8 Oct 2026 · flagger.app
Notifications
It can send deployment and canary result notifications to Slack, Microsoft Teams, Discord, and Rocket.Read 8 Oct 2026 · flagger.app
Project history
Flagger was initially developed at Weaveworks in 2018 by Stefan Prodan and became a CNCF project in 2020.Read 8 Oct 2026 · flagger.app
Project status
Flagger is a graduated Cloud Native Computing Foundation project and part of the Flux family of GitOps tools.Read 8 Oct 2026 · docs.flagger.app
Rollback
If SLO analysis detects a performance drop, Flagger automatically rolls back the release.Read 8 Oct 2026 · docs.flagger.app
Routing
Traffic routing uses an ingress controller or a service mesh compatible with the Kubernetes Gateway API.Read 8 Oct 2026 · flagger.app
Traffic shifting
It gradually shifts traffic to a new version while measuring metrics such as HTTP or gRPC request success rate and latency.Read 8 Oct 2026 · flagger.app
Validation
Built-in metric checks can be extended with custom metrics and webhooks for acceptance tests, load tests, or other validation.Read 8 Oct 2026 · flagger.app

Plans and prices

Flagger Free Apache 2.0 licensed · progressive delivery Kubernetes operator Read 8 Oct 2026 · flagger.app

Every Flagger plan and price →

Strong points and limits

Strong points

  • Supports canary, A/B, and blue/green releases
  • Automatic rollback on detected performance drops
  • Custom metrics and validation webhooks
  • Manual approval, pause, and resume controls

Limits

  • Requires a Kubernetes environment
  • Self-hosted deployment
  • Routing requires an ingress controller or compatible service mesh

Who it suits

Flagger suits teams running applications on Kubernetes that want automated release analysis and traffic shifting. It is a self-hosted option configured through Kubernetes custom resources.

Verdict

Flagger combines gradual traffic shifting with metric checks, manual gates, and rollback for Kubernetes releases. Its self-hosted model and Kubernetes configuration are central to its use.

Where Specifiction places it

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