How to convert JSON to YAML without breaking your config

Every JSON document is already valid YAML 1.2, so conversion is really about producing the readable YAML style — indentation instead of braces — while making sure no value silently changes type on the way.

A worked example

This JSON describes a service configuration:

{
  "service": "checkout", "replicas": 3, "debug": false,
  "country": "no", "enabled": "yes", "version": "1.10", "zip": "01234",
  "tags": ["web", "payments"],
  "env": { "LOG_LEVEL": "info", "TIMEOUT_MS": 2500 },
  "notes": null
}

The JSON ⇄ YAML converter (built on the js-yaml library) produces:

service: checkout
replicas: 3
debug: false
country: 'no'
enabled: 'yes'
version: '1.10'
zip: '01234'
tags:
  - web
  - payments
env:
  LOG_LEVEL: info
  TIMEOUT_MS: 2500
notes: null

Why some values are quoted

Look at 'no', 'yes', '1.10' and '01234'. Unquoted, a YAML parser could read them as something other than the strings they are in the JSON:

• no and yes are booleans in YAML 1.1, which many tools still use. This is the famous "Norway problem": a country code NO turning into false.
• 1.10 unquoted is the number 1.1 — a version string would lose its trailing zero.
• 01234 could be read as a number (and by some parsers as octal), losing the leading zero of a postal code.

The converter quotes these automatically. If you edit YAML by hand, quote any string that looks like a number, a date, a boolean or null.

Going the other way: YAML to JSON

Paste YAML and choose YAML → JSON. A few YAML features have no JSON equivalent and are resolved or dropped:

• Comments are discarded — JSON has none.
• Anchors and aliases (&defaults / *defaults) are expanded into full copies.
• Custom tags such as !Ref in CloudFormation templates aren't understood by the safe loader and produce an error rather than a guess.

So a YAML → JSON → YAML round trip gives equivalent data, not an identical file. Keep the YAML as the source of truth if it has comments you care about.