JSON to YAML

Paste JSON on the left and YAML appears on the right, indented two spaces per level. Swap the boxes to read YAML back.

An empty object or array is written in flow style as {} or [], because written in block form an empty collection would be a blank line.

Writing YAML is easy until you reach a string that would read back as something else. The value 12 as a string has to be written "12" or it returns as a number. So do true, null and ~, and yes is a boolean in YAML 1.1.

Strings starting with a marker need quotes too. A leading dash reads as a sequence entry, a leading hash starts a comment, and a colon followed by a space anywhere in the value splits it into a key and a value. Leading or trailing spaces are invisible in the file and would be lost.

This converter tests each string by reading it back. If a bare value would resolve to anything other than that exact string, it gets quotes. It also checks the older YAML 1.1 rules, which PyYAML and Ruby still use. So yes, NO, off, 1_000, 1:30 and a date like 2020-01-01 are quoted as well. Everything else stays bare, so the output reads like YAML a person wrote.

Since YAML 1.2, published in 2009, JSON is a strict subset of YAML. Every valid JSON file is a valid YAML file, and a conforming YAML parser will read it without complaint.

So this converter only reformats. The data doesn't change at all. The braces and brackets become indentation, the quotes come off the keys, and the commas go.

The relationship runs one way only. YAML has comments, anchors and several scalar styles, none of which JSON can hold, so the return trip loses whatever the file was using.

YAML to JSON is this converter reversed, and it explains what the reader will and won't accept. JSON to XML is the same idea for a format that needs a single root element.

For flattening a list of objects into rows instead, use JSON to CSV.