What happens if the same key appears twice?

The conversion stops and names the line. A JSON object cannot hold a key twice, and keeping the last one silently would change what your file means.

YAML to JSON

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YAML in

0 characters

JSON out

Runs entirely in your browser, nothing is uploaded.

How it works

YAML to JSON Converter with Line-Numbered Errors

Converts YAML to JSON, nested maps, block scalars, flow collections and multi-document files. A parse failure names the line that broke and why.

What this does

Nested mappings by indentation, including sequences of mappings and nested sequences
Block scalars | and > with strip, clip and keep chomping, plus an explicit indentation digit
Multi-document files split on --- and returned as a JSON array, with ... and %YAML directives handled
A leading zero keeps its value a string, so 01234 does not silently become 1234
Unsupported YAML raises a named error rather than a guess, anchors, merge keys and “? key” syntax all say what they are

FAQ

YAML type inference. Unquoted 1.10 is a float, so it becomes 1.1 and loses the trailing zero; unquoted true, false, null and ~ become JSON literals rather than strings; 0x1f and 0o17 are read as hexadecimal and octal. Two exceptions are deliberate here. A value with a leading zero such as 01234 is kept as a string, because it is almost always a zip code or an account number. And an integer too large to be a JavaScript safe integer is kept as a string as well, rather than being silently rounded. Quote anything that has to survive exactly.

This is a pragmatic subset, not a full YAML 1.2 implementation. Anchors and aliases (&name, *name), explicit tags (!!str, !Ref), merge keys (<<:), the explicit key form (? …) and flow collections spread over several lines each stop the conversion with an error naming what they are, rather than being read as plain text and producing quietly wrong JSON. Everything a normal config file uses is there.

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