YAML to JSON

What this tool does

Paste YAML and get JSON, with anchors expanded, block scalars folded into strings and multi-document streams turned into an array — one element per --- section. When the YAML does not parse, you get the line number, the column and the parser's own pointer under the offending character, plus an explanation of what that error usually means.

Parsing uses js-yaml's default schema, which supports the standard tags only. No tag in a pasted document can construct a JavaScript object, call a function or touch anything outside this page.

Common uses

• Feeding a Kubernetes manifest, a Compose file or a CI config to a tool that only reads JSON.
• Finding the indentation mistake in a 400-line values.yaml that a CI job rejected with an unhelpful message.
• Checking what a chain of &anchor and *alias references actually expands to.
• Reading OpenAPI or AsyncAPI specifications with JSON-oriented tooling.
• Converting front matter into data for a script.

A short example

This YAML, with an anchor and an alias:

limits: &res
  cpu: 500m
  memory: 512Mi
requests: *res

becomes JSON with the value written out twice:

{
  "limits": { "cpu": "500m", "memory": "512Mi" },
  "requests": { "cpu": "500m", "memory": "512Mi" }
}

Values that change type on the way through

YAML infers types from unquoted text, and the rules differ between YAML 1.1 and 1.2. This converter follows the 1.2 core schema. Four cases are worth checking in your own files:

• Dates become strings. when: 2026-09-24 is a timestamp in YAML, so it arrives in JSON as "2026-09-24T00:00:00.000Z" — a full UTC instant, not the date you typed. Quote it to keep the original text.
• Leading zeros are decimal here. 010 converts to 10. A YAML 1.1 parser such as PyYAML or Go's yaml.v2 reads the same text as octal 8.
• yes, no, on and off stay strings under the 1.2 core schema. Under 1.1 they are booleans — the reason a country code of NO famously turns into false in some pipelines.
• Version numbers lose a digit. 1.10 is the float 1.1. Always quote versions.

Worth knowing

Two things are rejected rather than guessed at. A tab character used for indentation is an error in YAML at any version — the spec allows tabs inside a scalar but never as indentation — and a key repeated inside the same mapping is refused here, because silently keeping the last value is how a config change disappears without trace. Comments are discarded, since JSON has nowhere to put them. And if a stream contains several documents, converting with First only deliberately drops the rest; the default wraps them in an array so nothing is lost.