Kubernetes ConfigMap data size limit

Direct answer

What is the rule?

The data stored in a Kubernetes ConfigMap cannot exceed 1 MiB; the specific enforcement action is not stated.

Scope

Kubernetes object limits, workload identity, and quota enforcement

Rule verified

August 14, 2026

Source checked

October 18, 2026

Worked check

Check your ConfigMap before deployment

Measure the rendered ConfigMap, not the YAML file length. This local Node.js check adds UTF-8 bytes in data to decoded bytes in binaryData. Keys and JSON formatting are not part of this particular data-size check.

1. Export one rendered v1 ConfigMap as JSON to a local file named configmap.json. Do not use a List or Secret. Keep confidential values on your machine.
2. Run the command below from that file’s directory. It reads standard input and prints byte totals only; nothing is uploaded to RuleRoster.
3. If the total exceeds 1,048,576 bytes, reduce the stored data or move large files to a suitable mounted volume or file service. Check application loading behavior before splitting configuration.

node -e 'const fs = require("node:fs");
const cm = JSON.parse(fs.readFileSync(0, "utf8"));
if (cm.apiVersion !== "v1" || cm.kind !== "ConfigMap") {
  throw new Error("Expected a v1 ConfigMap JSON object, not a Secret or List");
}
function entries(value) {
  if (value === undefined || value === null) return [];
  if (typeof value !== "object" || Array.isArray(value)) {
    throw new Error("Expected a map of strings");
  }
  return Object.entries(value).map(([key, text]) => {
    if (typeof text !== "string") throw new Error("Values must be strings");
    return [key, text];
  });
}
let bytes = 0;
for (const [key, text] of entries(cm.data)) {
  if (Object.hasOwn(cm.binaryData ?? {}, key)) throw new Error("Duplicate data key");
  bytes += Buffer.byteLength(text, "utf8");
}
for (const [, text] of entries(cm.binaryData)) {
  const decoded = Buffer.from(text, "base64");
  if (decoded.toString("base64") !== text) throw new Error("Expected canonical base64");
  bytes += decoded.length;
}
console.log(JSON.stringify({
  bytes, limitBytes: 1048576, withinDataLimit: bytes <= 1048576
}));' < configmap.json

Worked boundary example

A value containing é uses 2 UTF-8 bytes; binaryData containing AQID decodes to 3 bytes. Together they use 5 bytes, regardless of their key names. Exactly 1,048,576 data bytes passes this size check; one byte more does not.

This is not an API admission guarantee: invalid keys, metadata, quotas, policies, and immutable updates can still reject an object. The byte-counting behavior was checked against Kubernetes v1.34; confirm your cluster version before relying on it.

• Kubernetes ConfigMap documentation
• Kubernetes v1.34 validation source

Worked guidance reviewed September 20, 2026. This does not renew the published rule’s verification or source-check dates.

Evidence trail

Official sources

• Kubernetes ConfigMap documentation

  Kubernetes · verified August 14, 2026