Why Kubernetes Is Introducing KYAML: A Safer, JSON‑Like YAML Subset

YAML is ubiquitous in Kubernetes: NetworkPolicy, Deployment, Helm charts, and more.

Spaces and Quotes: Two Old Problems

YAML is extremely sensitive to spaces; a slight indentation mistake can cause Helm to fail. Optional quotes also create ambiguities, such as the “Norway Problem” where the unquoted country code NO is parsed as the boolean false. Another example shows a programmer named Richard Null whose Last_Name: Null without quotes is interpreted as a null value.

Some suggest switching to JSON, but JSON has its own drawbacks in Kubernetes contexts: no comments, mandatory quotes on all keys, and disallowed trailing commas.

"YAML Doesn't Have to Be This Bad"

The Kubernetes Enhancement Proposal KEP‑5295 aims to extract a reasonable grammar from the overly broad YAML spec and restrict it to Kubernetes use.

KYAML is a strict subset of YAML:

All KYAML files are valid YAML and can be fed directly to kubectl or Helm without extra flags.

String values must use double quotes.

Keys are unquoted unless ambiguity arises.

Objects (maps) use curly braces {}.

Arrays use square brackets [].

The overall style resembles JSON while retaining comments, trailing commas, and not requiring quotes on every key. Most importantly, KYAML no longer enforces strict indentation.

Official example:

$ kubectl get -o kyaml svc hostnames
---
{
  apiVersion: "v1",
  kind: "Service",
  metadata: {
    creationTimestamp: "2025-05-09T21:14:40Z",
    labels: { app: "hostnames" },
    name: "hostnames",
    namespace: "default",
    resourceVersion: "37697",
    uid: "7aad616c-1686-4231-b32e-5ec68a738bba"
  },
  spec: {
    clusterIP: "10.0.162.160",
    clusterIPs: [ "10.0.162.160" ],
    internalTrafficPolicy: "Cluster",
    ipFamilies: [ "IPv4" ],
    ipFamilyPolicy: "SingleStack",
    ports: [{ port: 80, protocol: "TCP", targetPort: 9376 }],
    selector: { app: "hostnames" },
    sessionAffinity: "None",
    type: "ClusterIP"
  },
  status: { loadBalancer: {} }
}

Community Reaction: Love‑Hate

Syntax debates are a traditional developer pastime. A Reddit user remarked, “It’s better than JSON, I understand why it’s stronger than YAML, but I still hate it.” The Go community already has unofficial KYAML parsers, and projects like StrictYAML are watching.

Kubernetes 1.34 is scheduled for an August release; will KYAML become the next cloud‑native standard? Time will tell.