What it does

Convert a document between JSON and YAML in either direction, in your browser. Going from JSON it produces block-style YAML; going from YAML it produces JSON. When a parse fails, the error names the exact line and column, and when a conversion loses something along the way, a note explains what and why.

The two directions

  • JSON to YAML. The JSON is first validated by the same precise, position-tracking parser the JSON formatter uses, so an invalid document is rejected with a line, column, and JSON Pointer path rather than a vague failure. The valid data is then written as block-style YAML.
  • YAML to JSON. The YAML is parsed under a JSON-compatible schema and serialized to JSON. Anchors and aliases (YAML's &name and *name reuse mechanism) are expanded inline, and block scalars (YAML's multi-line string styles) become ordinary JSON strings.

The quoting traps it handles

YAML is famously willing to read a bare word as something other than a string, which is where round-trips go wrong. The best-known case is the "Norway problem": the bare word NO is read as the boolean false, and the same happens to yes, on, and off, and to values like 1.0 (a number, not the string "1.0") and 08 (which is not valid octal). When emitting YAML, the converter quotes these values so that what you meant as a string survives as a string.

What conversion can lose

Some things exist in one format but not the other, so the notes flag them:

  • Comments. YAML has comments and JSON does not, so comments are dropped when converting YAML to JSON.
  • Anchors and aliases. These are expanded to their full value, so a compact shared reference in the source YAML becomes repeated data in the output.

Worked examples

  • JSON {"port":8080,"tls":true} becomes the YAML lines port: 8080 and tls: true.
  • YAML country: NO becomes JSON {"country":"NO"} on the way in, and when that is emitted back to YAML the value is quoted as country: "NO" so it is not mistaken for false.

Using it

Paste JSON to get YAML, or YAML to get JSON. Read the conversion notes when they appear: they tell you whether anything, such as a comment or an anchor, changed in a way you should be aware of. The conversion is deterministic for a given input.