YAML to JSON Converter

1. Paste YAML into the left pane or open a .yaml / .yml file. The JSON updates as you type.
2. If the status bar shows an error, go to the reported line and column. Tabs in indentation, a missing space after a colon and inconsistent indentation are the usual causes.
3. Choose a 2-space, 4-space or tab indent, then copy the JSON or download it.
4. Enable YAML 1.1 booleans to see how an older parser such as PyYAML would read yes, no, on and off.
5. Enable CloudFormation tags for templates that use !Ref, !Sub or !GetAtt; they become {"Ref": ...} and {"Fn::Sub": ...}.

An anchor (&name) labels a node, an alias (*name) reuses it, and the merge key << copies a mapping's keys into another mapping. Keys you write explicitly win over merged ones:

defaults: &defaults
  adapter: postgres
  pool: 5
production:
  <<: *defaults
  pool: 20

{
  "defaults": { "adapter": "postgres", "pool": 5 },
  "production": { "adapter": "postgres", "pool": 20 }
}

JSON has no references, so every alias is expanded into a full copy. A small file that aliases a large block many times can therefore produce much larger JSON. The merge key comes from YAML 1.1 and is not part of the YAML 1.2 core schema, but js-yaml and most other parsers still support it.

A literal block (|) keeps line breaks exactly, which is what you want for scripts and certificates. A folded block (>) joins lines with spaces, which suits long prose. The chomping indicator controls the final newline: by default one is kept, - strips it and + keeps all trailing blank lines.

script: |        →  "npm ci\nnpm test\n"
  npm ci
  npm test
message: >-      →  "Deploys the web tier"
  Deploys the
  web tier

Under YAML 1.1, a list of country codes like [se, no, dk] loads as ["se", false, "dk"], because no is a boolean. YAML 1.2 (2009) fixed this: its core schema only treats true and false as booleans. js-yaml follows 1.2, and these are the results this page actually produces:

The YAML 1.1 booleans option switches the first two rows to the 1.1 behaviour; it does not change how numbers are read. Many tools still use 1.1 rules, PyYAML among them, so the safe habit is to quote any string that could be mistaken for something else. The YAML 1.2.2 specification has the full core schema.

• tab characters must not be used in indentation: YAML forbids tabs for indentation. Replace them with spaces.
• duplicated mapping key: the same key appears twice in one mapping. Many parsers silently keep the last value; js-yaml refuses, which catches real mistakes in long config files.
• bad indentation of a mapping entry: often key: value: more on one line, or a child indented less than its siblings. Quote values that contain ": ".
• unknown tag !<!Ref>: a custom tag. Enable CloudFormation tags, or remove the tag.

Files such as kubectl output or Helm templates often contain several documents separated by ---. They are loaded with loadAll and returned as a JSON array with one element per document; empty documents, such as one after a trailing ---, are skipped and the status bar says so. To go the other way, use the JSON to YAML converter, or tidy the source with the YAML formatter and inspect the result in the JSON viewer.