Flux CD vs. Argo CD: GitOps Tools Comparison

Kubernetes is a versatile container orchestration platform, but it lacks built-in mechanisms for automating app deployment. GitOps-powered continuous delivery (CD) workflows provide the answer, enabling cluster resources to auto-update whenever changes are made to your Git repository.

Flux and Argo CD are the two most popular tools for implementing GitOps with Kubernetes. They continually sync the states of Kubernetes objects against declarative config files stored in your repository. This simplifies deployment management at scale and helps prevent configuration drift.

Flux and Argo CD are both feature-filled tools that provide many benefits for developers and cluster operators. As a result, DevOps teams often find it difficult to choose between them. This article will explain how they compare on key points, including their architectures, ease of use, and multi-tenancy support. You’ll then be ready to choose the best option for your next project.

1. What is GitOps?
2. What is Flux CD?
3. What is Argo CD?
4. Differences between Flux and Argo CD
5. Should I Use Flux or Argo CD?

GitOps is a software development methodology that uses versioned files in Git repositories as the source of truth for your workflows. Moreover, live infrastructure and app updates are applied by automated tools that continually monitor your repositories for changes. When a change is found, then the tool applies actions that reconcile your cluster’s state, such as by creating or replacing Kubernetes objects.

GitOps has many benefits, including less manual configuration, improved scalability, and the option of easily replicating different deployments by connecting multiple environments to one repository. 

GitOps is also one of the best ways to prevent configuration drift, the phenomenon where live environments end up differing from the states defined in your repositories. For example, a GitOps tool would automatically restore the correct state if a user accidentally makes a manual edit to a Kubernetes object.

Flux CD is a GitOps-based continuous delivery tool for Kubernetes. It provides a set of Kubernetes controllers that monitor your Git repositories for changes and then automatically add, replace, and remove Kubernetes cluster objects in response.

Flux CD is a graduated project within the Cloud Native Computing Foundation (CNCF). It was originally developed at Weaveworks before the company’s closure earlier this year. Flux remains in development by the community and is supported by many major DevOps services, helping to ensure its longevity.

Flux aims to provide a toolkit for implementing GitOps best practices in Kubernetes clusters. Every part of its configuration can be defined in code, letting you use GitOps to manage Flux itself. Internally, the tool uses the standard Kubernetes API to interact with your cluster.

Flux features

• GitOps automation: Syncs Kubernetes clusters with Git as the single source of truth.
• Kubernetes native: Seamlessly integrates with Kubernetes using CRDs and APIs.
• Multi-environment support: Manages deployments across multiple environments (dev, staging, prod).
• Auto-updates: Monitors registries for new container images and updates workloads automatically.
• Modular architecture: Supports Helm, Kustomize, and raw manifests with flexible feature toggles.
• Secure: Pull-based updates with secure Git access via SSH or HTTPS.

To learn more, see our Flux CD tutorial.

Argo CD is also a declarative Kubernetes GitOps continuous delivery tool. It’s part of the Argo project, a collection of open-source tools that implement useful features missing from standard Kubernetes.

Argo CD’s comprehensive range of features has helped it find broad appeal. Although not a perfect indicator of popularity, Argo CD has over 17.8k GitHub stars, compared with 6.5k stars for Flux 2. Key to Argo’s success is its ease of use, including a fully-featured web interface and SSO-based access management system.

Argo CD is designed to simplify the whole process of deploying and maintaining Kubernetes apps. The custom resources it provides let you easily define deployment configurations in code, using a simplified set of abstractions. This makes it a great option when you want to get started quickly with a developer-friendly tool.

Argo CD features

• GitOps-based: Synchronizes Kubernetes clusters with Git as the single source of truth, ensuring the cluster state matches the desired state.
• Declarative UI and CLI: Provides an intuitive web-based dashboard and CLI for managing deployments and visualizing application states.
• Multi-cluster support: Easily manages and deploys applications across multiple Kubernetes clusters from a single interface.
• Application rollbacks: Enables quick rollbacks to a previous application state in case of issues, ensuring stability.
• Integration with Helm and Kustomize: Supports popular tools like Helm charts, Kustomize overlays, and plain Kubernetes manifests.
• Real-time sync and alerts: Continuously monitors applications for drift and sends alerts for out-of-sync states, with optional auto-sync to fix discrepancies.

To learn more, see our Argo CD tutorial.

Flux CD and Argo CD are both Kubernetes-native GitOps tools for continuous delivery, but Flux CD emphasizes simplicity and seamless integration with Kubernetes, while Argo CD offers a richer user interface, application-centric management, and advanced features like multi-cluster support and self-healing. 

Let’s analyze how they compare across key features to uncover their strengths and weaknesses.

1. Architecture

Flux’s core components are referred to as a “GitOps Toolkit.” They provide APIs, Kubernetes controllers, and tools that implement GitOps-driven continuous delivery to Kubernetes. The Source Controller monitors your repositories for changes before other controllers apply actions to update your cluster. 

The system is configured using either the CLI or declarative config files that let you manage Flux with Flux.

Argo CD has a similar fundamental architecture. It also provides Kubernetes controllers that monitor your connected source repositories for changes. You can manage your apps with the CLI, declarative configuration via Kubernetes CRDs, or the detailed web interface.

Both tools are, therefore, fundamentally similar in how they’re used and how they work. However, Flux is designed to be an extensible toolkit, whereas Argo CD is positioned as a complete app. Argo can, hence, feel more opinionated than Flux.

2. App deployment process

Flux CD and Argo CD offer the same high-level deployment process. You register your apps using either the CLI or Kubernetes CRDs, specifying the source (such as a Git repository or Helm chart) to connect to. The tools then fetch the state from the repository and deploy your app into your cluster.

When you’re ready to apply an update, you simply push to your repository. The tool will then sync your changes into your cluster, either when requested manually or automatically on a preconfigured schedule.

Both tools include support for Kustomize templates and Helm charts, although Argo doesn’t actually use Helm internally—it manages your releases itself. This addresses some of the problems with Helm, such as its awkward CRD management, but means you can’t use familiar helm commands to manage your release history.

3. Reconciliation process

Reconciliation, also known as synchronization, is the process of comparing the states of your cluster and repository and applying any required changes. Both Flux and Argo CD provide options for manually initiating reconciliation using the CLI—or, in Argo’s case, the web UI—and setting up automatic periodic resyncs.

There are some differences in how sync configuration is managed. For instance, Argo only allows you to set the automatic sync interval at the instance level, not for individual apps. 

Argo also lacks an intuitive method of temporarily pausing reconciliation, such as when you need to initiate a deployment freeze. On the flip side, Argo lets you choose from multiple strategies to decide whether an app is out of sync.

4. Declarative configuration

As GitOps tools, Flux and Argo CD both strongly support declarative configuration. You can manage them using Kubernetes CRDs. Flux offers resources like GitRepository and Kustomization, while Argo favors a higher abstraction level with Applications and Application Sets.

Argo CD also supports an “app of apps” pattern that makes it easier to deploy a group of related applications. Flux doesn’t have a direct equivalent, but you can include multiple HelmRelease or Kustomization objects in a single deployment.

Flux also uses declarative configuration to manage its own installation in your cluster. When you install Flux, you must create or specify a Git repository that will store the config manifests used by Flux itself. This allows you to exactly reproduce your environment in the future.

5. Ease of use

Flux and Argo CD are both supported by a robust CLI and clear documentation, which makes them easy to use. However, Flux’s toolkit ethos and slightly lower-level config mechanism mean it has a somewhat steeper learning curve than Argo. 

Argo’s built-in web interface also helps make it more accessible, removing the need to learn CLI commands to perform key tasks.

6. Interface options

Flux is administered using its comprehensive CLI. A web interface called Capacitor is available but must be installed separately. It mainly provides visibility into what’s deployed, but limited controls let you perform tasks such as requesting reconciliation or retrieving an app’s logs.

Screenshot of Capacitor 

Argo ships a feature-complete web UI by default, in addition to its robust CLI, making it the clear winner in this category. Argo’s UI lets you visualize every part of your app, including the relationships between components and their sync statuses. You can initiate resyncs, roll back to a previous release, and create and update your app definitions, all without leaving the interface.

Screenshot of Argo CD 

7. Integrations, customization, and extension options

Flux has a healthy ecosystem of partner integrations. It’s supported by several managed Kubernetes services and app deployment platforms, including Amazon’s EKS Anywhere, Azure AKS with Arc, and VMware’s Tanzu. 

Several community projects integrate Flux with popular DevOps tools, including observability platforms and IaC providers. Documentation is also available to write your own Flux extensions that can monitor for source changes and implement support for additional repository types.

Argo CD is less customizable as it’s designed to be a complete end-to-end platform. You can write extensions for its web interface and use a basic plugin system to template parts of your config file, but options are limited compared to Flux.

Flux’s focus on providing a collection of extensible components makes it the obvious choice when you’re planning to build custom tooling on top. These benefits mean it’s becoming the preferred option for external vendors developing Kubernetes GitOps solutions. For example, GitLab is integrating Flux with its CI/CD system, letting you deploy and monitor Flux apps directly from GitLab repositories.

8. Access management

Flux doesn’t have its own access management system. You must use the standard Kubernetes identity, and RBAC controls to configure who can interact with your Flux resources. This standardizes all access controls in the familiar Kubernetes RBAC mechanism, but can make it challenging to enforce granular policies at scale.

Argo comes with its own user system that lets you decouple access control from your cluster-level Kubernetes users. You can create Argo users by adding “local” users to a ConfigMap or connecting your SSO provider. Identity services including Auth0, Google, Microsoft, Okta, and Zitadel are supported. Once you’ve added your users, Argo’s RBAC layer lets you precisely configure the actions they can perform.

9. Multi-tenancy support

Multi-tenancy refers to the use of one Kubernetes cluster to run multiple apps belonging to different projects or teams. The deployments must be isolated so the teams can’t interact with each others’ apps. Flux and Argo CD both have integrated multi-tenancy support, allowing several tenants to be served by one installation of the tool.

Flux’s implementation is based on standard Kubernetes namespaces and RBAC controls. To limit their capabilities, you can have Flux controllers impersonate a specific Kubernetes Service Account. This functionality must be manually enabled.

Argo CD is deployed in multi-tenant mode by default. It uses its included RBAC system to let you set policies for your apps, restricting which users can access them. You can use the SSO integration to identify tenants and their users based on your existing identity provider configuration.

10. Scalability

Flux and Argo CD can each scale to handle large-scale app deployments. There are no significant differences in what they can theoretically support.

Flux comes with detailed guides for tuning scaling options so you can manage “tens of thousands” of apps with one installation. Argo doesn’t advertise a scaling limit; however, web UI slowdowns reportedly occur as app counts reach 3,000-5,000 deployments. 

Analysis by Akuity found the system can nonetheless scale to 50,000 apps and 1,000 connected clusters, when the UI is modified to enable list pagination. This change remains an open issue in the Argo project’s backlog.

11. Community adoption, support, and maintenance

Both Flux and Argo CD are actively supported tools with regular new releases. They’re each known to be used at major organizations: Argo CD lists Adobe, Mercedes-Benz, and Red Hat among its users, while Flux has been chosen by teams at Anchore, Ring Central, and Volvo. Whichever you choose, you’ll be in good company.

The solutions both have comprehensive documentation, highly active communities, and a wealth of third-party learning material available. They’re open-source CNCF utilities, with Argo CD originating from Intuit and Flux from Weaveworks. Although Flux’s future was in doubt after Weaveworks ceased operations, ControlPlane has provided new backing to allow some of the previous core maintainers to continue their work.

Flux vs ArgoCD: Table comparison

Here’s a summary table of all the points we’ve discussed. Use it to quickly compare the tools across the features that matter most for your use case.

Flux would be better if you want to stay closer to pure Kubernetes and are happy with a little more hands-on work. Argo is a powerful alternative if you’d like a more rounded but opinionated platform-like experience. 

But ultimately, there’s no right answer for which you should choose.

Argo CD is popular because it’s approachable, easy to learn, and packed with useful convenience features. For example, the included web dashboard and custom access management solution let developers easily monitor deployment status, even if they’re not specifically skilled in CI/CD. 

Conversely, Flux’s “toolkit” approach makes it easier to customize. There are also signs that the DevOps ecosystem is leaning towards Flux as the default tool for Kubernetes GitOps, such as GitLab’s decision to integrate Flux tightly with its platform.

We’ve seen that both Flux and Argo CD offer compelling features for implementing GitOps-based continuous delivery to Kubernetes clusters. The best option for your use case depends on the features you need and the experience you’re looking for.

Spacelift is an IaC management platform that uses GitOps to automate CI/CD for your infrastructure components. It supports OpenTofu, Terraform, Terragrunt, CloudFormation, Pulumi, Kubernetes, and Ansible.

The power of Spacelift lies in its fully automated hands-on approach. Once you’ve created a Spacelift stack for your project, changes to the IaC files in your repository will automatically be applied to your infrastructure. 

Spacelift’s pull request integrations keep everyone informed of what will change by displaying which resources are going to be affected by new merges. Spacelift also allows you to enforce policies and automated compliance checks that prevent dangerous oversights from occurring.

Spacelift includes drift detection capabilities that periodically check your infrastructure for discrepancies compared to your repository’s state. It can then launch reconciliation jobs to restore the correct state, ensuring your infrastructure operates predictably and reliably.

With Spacelift, you get:

• Policies to control what kind of resources engineers can create, what parameters they can have, how many approvals you need for a run, what kind of task you execute, what happens when a pull request is open, and where to send your notifications
• Stack dependencies to build multi-infrastructure automation workflows with dependencies, having the ability to build a workflow that, for example, generates your EC2 instances using Terraform and combines it with Ansible to configure them
• Self-service infrastructure via Blueprints, or Spacelift’s Kubernetes operator, enabling your developers to do what matters – developing application code while not sacrificing control
• Creature comforts such as contexts (reusable containers for your environment variables, files, and hooks), and the ability to run arbitrary code
• Drift detection and optional remediation

If you want to learn more about Spacelift, create a free account today or book a demo with one of our engineers.

We’ve explored the key features, similarities, and differences of Flux and Argo CD. Whichever one you use, you’ll get a powerful Kubernetes GitOps workflow that lets you fully automate your apps deployment.

However, Flux and Argo are just one part of a complete GitOps implementation. You also need IaC tools like Terraform, Ansible, and Pulumi to provision your clusters in your cloud accounts, ready to deploy your apps to.