OPA Gatekeeper vs Kyverno vs Kubewarden — Kubernetes Policy Engine Comparison

Every Kubernetes cluster eventually needs policy enforcement — blocking privileged containers, requiring resource limits, restricting image registries. The question isn't whether you need a policy engine, it's which one fits your team.

The Three Contenders

OPA Gatekeeper — built on Open Policy Agent, policies written in Rego, the most mature and widely adopted option.

Kyverno — policies written as native Kubernetes YAML, no new language to learn, CNCF graduated project.

Kubewarden — policies compiled to WebAssembly, can be written in Rego, Go, Rust, or any language with a WASM target.

The Same Policy, Three Ways

Requiring resource limits on every container — OPA Gatekeeper:

package k8srequiredresources
 
violation[{"msg": msg}] {
    container := input.review.object.spec.containers[_]
    not container.resources.limits.memory
    msg := sprintf("Container %v must specify memory limits", [container.name])
}

Plus a separate ConstraintTemplate and Constraint CRD to actually apply it — three files total for one rule.

Same policy — Kyverno:

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-resource-limits
spec:
  validationFailureAction: Enforce
  rules:
  - name: check-resources
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "Memory limits are required"
      pattern:
        spec:
          containers:
          - resources:
              limits:
                memory: "?*"

One file, no new language, readable by anyone who already knows Kubernetes YAML.

Same policy — Kubewarden (using the generic pattern policy, or a Rego-compiled module):

apiVersion: policies.kubewarden.io/v1
kind: ClusterAdmissionPolicy
metadata:
  name: require-resource-limits
spec:
  module: registry://ghcr.io/kubewarden/policies/safe-labels:v0.2.0
  rules:
  - apiGroups: [""]
    apiVersions: ["v1"]
    resources: ["pods"]
    operations: ["CREATE"]
  mutating: false

Kubewarden's syntax depends entirely on which policy module you use — if you write your own in Go or Rust, you get full programming language power, but you're compiling and distributing a WASM binary instead of writing YAML.

Real Differences That Matter

Learning curve. Kyverno wins decisively here. If your team already writes Kubernetes manifests, Kyverno policies look familiar immediately. Rego has its own syntax and mental model (it's a logic/query language, not imperative) — expect a real learning investment for OPA. Kubewarden's curve depends on which language you pick for policy authoring.

Mutation support. All three can mutate resources (e.g., auto-inject labels, sidecars, default resource limits), but Kyverno's mutation syntax is noticeably more intuitive — it's a patch-style syntax matching what you're used to from kubectl patch.

# Kyverno mutation — auto-add a label if missing
mutate:
  patchStrategicMerge:
    metadata:
      labels:
        managed-by: platform-team

Performance at scale. OPA Gatekeeper has the most production track record at very large scale (thousands of nodes, high admission request volume) because Rego's evaluation engine has been optimized longest. Kyverno has closed most of this gap in recent versions but historically used more CPU for complex policy sets.

Ecosystem and policy libraries. OPA/Gatekeeper has the largest collection of community policies (Gatekeeper Library). Kyverno's policy library (kyverno.io/policies) has grown fast and covers most common compliance needs (Pod Security Standards, image verification, etc.) out of the box.

Image signature verification. This is where Kyverno has a real edge — built-in support for Cosign/Sigstore image verification is first-class:

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: verify-image-signature
spec:
  rules:
  - name: check-signature
    match:
      resources:
        kinds:
        - Pod
    verifyImages:
    - imageReferences:
      - "myregistry.io/*"
      attestors:
      - entries:
        - keys:
            publicKeys: |-
              -----BEGIN PUBLIC KEY-----
              ...
              -----END PUBLIC KEY-----

OPA/Gatekeeper and Kubewarden can do this too but require more setup glue.

Honest Recommendation

Use Kyverno if: your team is Kubernetes-native and doesn't want to learn Rego, you need fast policy authoring, and image signing/supply chain policies matter to you. This is the right default for most teams starting fresh in 2026.

Use OPA Gatekeeper if: you're already using OPA elsewhere (API gateways, CI/CD policy checks) and want one policy language across your whole stack, or you're at a scale where OPA's maturity and performance track record matters more than authoring convenience.

Use Kubewarden if: you want policies written in a real programming language with full testing/debugging tooling (unit tests in Go or Rust, not Rego's more limited test framework), or you're building a product that needs to ship custom policy logic to customers as a distributable artifact.

For a typical platform team in 2026, Kyverno is the pragmatic default. Reach for OPA only if you have an existing organizational investment in Rego, and reach for Kubewarden only if WASM portability is a genuine requirement, not a nice-to-have.

Set up policy enforcement: Kyverno Kubernetes Policy Engine Complete Guide