10 Reasons For Kyverno, Admission Controller, Kyverno Vs OPA

Kubernetes users choose Kyverno over OPA Gatekeeper because Kyverno policies are plain Kubernetes YAML instead of Rego. Kyverno also mutates and generates resources, applies policies to existing resources, supports policy exceptions natively, and ships a large ready-made policy library. Teams that work mainly in Kubernetes get to working policies faster, with fewer moving parts.

Admission controllers are one of the main ways to enforce security, compliance and operational best practices in Kubernetes. They act as “gatekeepers”, inspecting and validating resources before they’re admitted into the cluster.

OPA/Gatekeeper has long been a go-to choice for policy enforcement in Kubernetes. Kyverno, designed specifically for Kubernetes users by Nirmata, has quickly gained popularity as a Kubernetes-native alternative with a simpler approach to policy management.

At Nirmata, we’ve worked with several customers to help them migrate to Kyverno. Based on their experiences, here are the top 10 reasons why DevOps users prefer Kyverno over other admission controllers. For a feature-by-feature view, read our Kyverno vs OPA Gatekeeper comparison.

What are the 10 reasons at a glance?

#	Reason	Kyverno	OPA Gatekeeper
1	Policy language	YAML, like Kubernetes manifests	Rego
2	Design	Built for Kubernetes	General-purpose engine, adapted
3	Mutation	YAML-based patches	“Assign”, more complex
4	Resource generation	Built in	Not built in
5	Existing resources	Policies apply to deployed resources	Focus on admission time
6	Policy library	Curated, Kubernetes-focused	Smaller curated library
7	Targeting	Match and exclude rules, like Kubernetes selectors	–
8	Policy exceptions	Built in	Custom logic or external tools
9	Testing	Integrated into policy workflow	Gator
10	Community	Kubernetes-focused	Active, broader scope

How is writing Kyverno policies different?

1. Simplified policy definition with YAML. Kyverno uses YAML for policy definitions, the same format as Kubernetes manifests. Writing and reading policies feels natural for Kubernetes users. Gatekeeper uses Rego, a purpose-built language with a steep learning curve.

“Writing policies in Gatekeeper was quite difficult… Kyverno felt like working with familiar Kubernetes selectors.”

2. Kubernetes-native by design. Kyverno was built from the ground up for Kubernetes. It runs as a Kubernetes admission controller and is tightly integrated with the Kubernetes ecosystem. Gatekeeper was adapted for Kubernetes but started as a general-purpose policy engine. Kyverno’s approach means simpler setup, fewer components and smoother operations.

3. Mutation that’s easy to write. Both tools now support mutation, but Kyverno’s implementation is widely considered more user-friendly. Adding labels or enforcing resource limits is a YAML-based patch. Gatekeeper’s “Assign” feature is more complex and can be harder to work with in practice.

What can Kyverno automate that Gatekeeper can’t?

4. Built-in resource generation. Kyverno can generate Kubernetes resources automatically from policy definitions, such as NetworkPolicies or default ConfigMaps. This helps enforce compliance and security out of the box. Gatekeeper has no built-in resource generation, so Kyverno is the stronger choice for proactive configuration.

5. Apply policies to existing resources. Kyverno supports dynamic enforcement on existing resources, in addition to admission time. You can update a policy and apply it retroactively to resources that are already deployed. Gatekeeper primarily focuses on admission-time validation and doesn’t natively support this.

How do the policy library, targeting and exceptions help?

6. Extensive policy library. Kyverno offers a rich library of pre-defined policies, covering everything from Pod Security Standards (PSS) to Kubernetes configuration best practices. Users get a head start and spend less time authoring new policies. Gatekeeper provides a framework but lacks a curated, Kubernetes-focused policy library at the same scale.

7. Granular policy targeting. With match and exclude rules in YAML, Kyverno gives fine-grained control over where and how policies apply, based on labels, annotations, kinds, namespaces and more. This mirrors Kubernetes’ own selectors, so policy behavior is predictable.

8. Integrated policy exceptions. Kyverno has built-in exception handling: you define the resources or conditions where a policy should not apply. That handles edge cases without turning enforcement off. Gatekeeper does not natively support policy exceptions and needs custom logic or external tools. See temporary policy exceptions with Kyverno for an example.

How do testing and community compare?

9. Testing and simulation. Kyverno includes tools for testing and simulating policies before you roll them out. You can check how a policy behaves against sample resources and catch problems early. Gatekeeper has tools like Gator, but Kyverno’s built-in testing is more tightly integrated into the policy development workflow.

10. A Kubernetes-focused community. Kyverno’s open-source community is growing fast and focuses specifically on Kubernetes use cases. Regular releases, strong documentation and community support keep the tool moving. OPA/Gatekeeper also has an active community, but Kyverno’s Kubernetes-centric momentum is a big draw for platform teams.

Ready to try it? The Kyverno open source page and the Kyverno playbook are good places to start.

What advanced capabilities does Kyverno add?

Kyverno also has advanced features that Gatekeeper doesn’t offer natively:

Cleanup Policies: Kyverno automatically removes resources based on defined criteria, which suits ephemeral workloads or cleanup after testing.
Image Verification: Ensure OCI-compliant supply chain security, verify image signatures, and perform registry lookups, all natively supported in Kyverno.

These features make Kyverno a full Kubernetes solution for both security and operational governance.

Is Kyverno the right choice for your team?

Both Kyverno and OPA/Gatekeeper are capable tools for managing Kubernetes policies. If you want something that is easy to learn, Kubernetes-native and has powerful features out of the box, Kyverno is hard to beat. YAML policies, built-in mutation, generation and exception handling let platform and security teams roll out policies with confidence across Kubernetes environments.

Planning a move? Read the OPA to Kyverno guide and how Wayfair migrated from OPA to Kyverno.

Want to learn more or see Kyverno in action? Request a demo to see how Nirmata can strengthen Kubernetes governance in your organization. Have a question about what you’ve just read? Reach out to us, and we’ll get back to you promptly.

References

Frequently asked questions

How hard is it to migrate from Gatekeeper to Kyverno?

Policies have to be rewritten, because Kyverno doesn't run Rego. Most teams start by matching each Gatekeeper constraint to an equivalent in the Kyverno policy library, then deploy the Kyverno versions in Audit mode next to Gatekeeper, compare the reports, and switch to Enforce once results agree. Our OPA to Kyverno guide walks through the process.

What is a Kyverno PolicyException?

A PolicyException is a separate Kubernetes resource that names a policy, the rules inside it, and the resources those rules should skip. Because it lives outside the policy, a team can request an exemption for one workload without editing a cluster-wide policy, and platform teams can review exceptions through the same Git and RBAC workflow as any other resource.

How do Kyverno cleanup policies work?

A CleanupPolicy or ClusterCleanupPolicy uses the same match and exclude blocks as other Kyverno policies, adds optional conditions, and runs on a cron schedule. On each run, Kyverno deletes the resources that match. Kyverno can also remove individual resources that carry a time-to-live label, which suits short-lived test namespaces and temporary workloads.

Which image signature formats can Kyverno verify?

Kyverno's verifyImages rules check signatures and attestations made with Sigstore Cosign and with Notary. A rule can require a signature from a given key, certificate or keyless identity, check attestations such as vulnerability scans or SBOMs, and replace image tags with digests so the image that was verified is the one that runs.