JSON vs YAML syntax

Basic types

{
  "name": "Ana",
  "age": 32,
  "active": true,
  "notes": null,
  "tags": ["admin", "beta"]
}

name: Ana
age: 32
active: true
notes: null
tags:
  - admin
  - beta

Nested objects

{
  "address": {
    "city": "Paris",
    "zip": "75001"
  }
}

address:
  city: Paris
  zip: "75001"

Rules to remember

	JSON	YAML
Comments	not supported	yes, with `#`
Indentation	free (braces)	meaningful, spaces only
Quotes on strings	required	optional unless ambiguous
Trailing comma	forbidden	not applicable
Multi-line strings	no	yes, with `

In YAML, yes, no, on, off, true, false are sometimes parsed as booleans depending on the parser. Quote them if you want a real string: country: "no".

References and anchors in YAML

defaults: &defaults
  adapter: mysql
  timeout: 30

development:
  <<: *defaults
  database: dev_db

test:
  <<: *defaults
  database: test_db

&defaults defines a reusable anchor, <<: *defaults merges it into another block — handy for not repeating shared configuration.

When to choose which

Context	Preferred format	Why
REST API, data exchange	JSON	Native in JavaScript, a parser is everywhere
Configuration files	YAML	More readable for humans, comments allowed
Docker Compose, CI/CD, Kubernetes	YAML	The DevOps ecosystem's standard
Strict storage/serialisation	JSON	Unambiguous syntax, no indentation traps

YAML indentation must use spaces, never tabs — mixing the two is the most common mistake, and it usually produces a confusing parse error.

Basic types

Nested objects

Rules to remember

References and anchors in YAML

When to choose which

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