Convert between YAML and JSON formats with validation, formatting, and error highlighting.
Drop a YAML document into this tool and it re-emits the same data as JSON, resolving every unquoted scalar to a concrete type: `true` becomes a boolean, `42` a number, everything else a string. It formats the output, highlights syntax errors with line and column, and converts in the reverse direction when you paste JSON. The conversion runs entirely in the browser; nothing is uploaded. The first thing people trip on is that YAML guesses types: values you think of as text, such as `yes`, `on`, or `0123`, can come out as booleans or numbers unless they were quoted. The output shows exactly what a parser would hand your code.
A concrete input and expected output from the current implementation.
Input
name: Apollo enabled: true count: 42 tags: - yaml - json notes: | line one line two
Expected output
{
"name": "Apollo",
"enabled": true,
"count": 42,
"tags": [
"yaml",
"json"
],
"notes": "line one\nline two\n"
} YAML resolves unquoted `true` and `42` into JSON's boolean and number types, and the indented list under `tags` becomes an array of strings. The literal block after `|` becomes a string that keeps its line breaks, including the final one (default clip chomping), so JSON escapes it as `\n`.
The document is parsed by indentation: nested blocks become nested objects and arrays, and each unquoted scalar is resolved by pattern into a JSON type. Booleans, integers, floats, and null are detected; everything else, including version-like strings such as 1.2.0, stays a string. Quoting forces a string. Parse errors such as tabs inside indentation or an undefined alias are reported with line and column and highlighted in the input pane.
The resolved tree is serialized as JSON with your chosen indentation: strings are quoted with escaping, while booleans, numbers, and null appear unquoted. Keys become strings because JSON requires it. Block scalars arrive as strings that keep their internal line breaks, including the trailing newline, shown escaped as \n. Multi-document streams and anchors have no JSON equivalent and need special handling, so verify unusual input against the source.
Under YAML 1.1-style resolution, `on`, `off`, `yes`, and `no` are booleans, so `on` becomes true; under strict YAML 1.2 rules it would stay the string "on". Quote the value, `"on"`, to force a string. The same applies to `0123`, which is octal (83) under 1.1 rules and a plain string under 1.2.
No. JSON to YAML is essentially lossless because every JSON document is valid YAML, but the reverse direction drops comments, anchors, aliases, and tags, and unquoted scalars can resolve differently on the way back. Use this tool to translate data or inspect what a parser sees, not to edit and restore the same file.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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