Kyverno vs. OPA: Kubernetes Policy Engines

In this article, we’ll explore what Kyverno and OPA are, how they work, and which one might be right for your organization.

What Is Kyverno?

Kyverno is a Kubernetes-native policy engine created by Nirmata. It is designed specifically for Kubernetes and runs as an admission controller inside the cluster. Kyverno lets you define and enforce policies using Kubernetes Custom Resources (CRDs), which makes it especially intuitive for users already comfortable with Kubernetes YAML.

Kyverno policies can:

• Validate resources before they are created or updated
• Mutate configurations (e.g., add labels or annotations automatically)
• Generate other resources (e.g., inject a NetworkPolicy when a new namespace is created)

A simple example of a Kyverno validation policy:

  apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: restrict-image-registries
spec:
  validationFailureAction: enforce
  rules:
  - name: only-allow-approved-registries
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "Only images from approved registries are allowed."
      pattern:
        spec:
          containers:
          - image: "registry.company.com/*"

Why People Like Kyverno

• Uses native Kubernetes YAML — no need to learn Rego or custom languages
• Works out-of-the-box in Kubernetes clusters
• Can mutate and generate resources, not just validate
• Strong community support and growing adoption (graduated CNCF project as of 2024)

What Is OPA (Open Policy Agent)?

OPA, or Open Policy Agent, is a general-purpose policy engine created by Styra. Unlike Kyverno, OPA is not Kubernetes-specific — it can be used with APIs, CI/CD pipelines, Terraform, and more.

OPA is often used with Gatekeeper, which is a Kubernetes admission controller built on top of OPA. Gatekeeper enforces OPA policies in Kubernetes clusters.

OPA policies are written in a declarative query language called Rego, which allows for expressive and powerful logic — though it has a learning curve.

Here’s a simple OPA policy written in Rego to block privileged containers:

  package kubernetes.admission

violation[{"msg": msg}] {
  input.review.object.spec.containers[_].securityContext.privileged == true
  msg := "Privileged containers are not allowed."
}

OPA is highly flexible and is often used in complex scenarios that go beyond Kubernetes. For example, you can use OPA to:

• Block certain container registries
• Enforce team-specific naming conventions
• Validate Terraform configurations
• Apply policies in microservices APIs

Why People Use OPA

• Powerful and flexible policy language (Rego)
• Works across multiple domains (not just Kubernetes)
• Rich ecosystem of integrations (Terraform, Envoy, CI/CD pipelines)
• Backed by the CNCF and used by major companies like Netflix and Capital One

Kyverno vs. OPA: A Comparison

Which One Should You Choose?

It depends on your goals and your team’s skill set.

• Choose Kyverno if you want a Kubernetes-native experience, need to mutate or generate resources, and prefer writing policies in YAML. Kyverno is ideal for platform engineers who want to enforce Kubernetes best practices quickly and intuitively.
• Choose OPA if you need a cross-platform policy engine, want fine-grained control with a powerful language, or already use OPA elsewhere in your stack. Gatekeeper is also a good fit if you’re already invested in Rego-based policies.

Final Thoughts

Both Kyverno and OPA solve the same problem: policy enforcement in Kubernetes. But they come at it from different angles. Kyverno is tailor-made for Kubernetes and offers simplicity. OPA offers deep power and flexibility with a steeper learning curve.

If your team is just getting started with Kubernetes policies, Kyverno may be the fastest way to get results. If you’re building a broader policy framework across your cloud infrastructure, OPA may be the better long-term investment.

Whichever you choose, implementing policy as code is a critical step in running secure, compliant, and well-managed Kubernetes environments.