JSON vs YAML: What's the Difference?

What are JSON and YAML?

JSON (JavaScript Object Notation) is a lightweight text format for data interchange. Introduced in the early 2000s alongside the rise of REST APIs, it became the universal language of web services — simple, strict, and machine-friendly.

YAML (YAML Ain't Markup Language) is a human-readable data serialization format designed for configuration files. It prioritizes readability: less punctuation, support for comments, and a clean indentation-based structure.

Both formats represent the same underlying data model — objects, arrays, strings, numbers, booleans, and null — but they make very different trade-offs.

Syntax comparison

The same data expressed in both formats:

{
  "name": "Jane Doe",
  "age": 32,
  "active": true,
  "roles": ["admin", "editor"],
  "address": {
    "city": "Paris",
    "country": "France"
  }
}

name: Jane Doe
age: 32
active: true
roles:
  - admin
  - editor
address:
  city: Paris
  country: France

Both represent exactly the same data. YAML removes the quotes, braces, and commas — indentation does the structural work instead.

This site's YAML ↔ JSON Converter switches between the two blocks above instantly, in either direction.

Key differences

YAML-only features

Comments

YAML supports comments — JSON does not# Database configuration
database:
  host: localhost   # or use an env var
  port: 5432
  name: myapp_prod

Multi-line strings

YAML literal block ( | ) and folded block ( > )description: |
  This is a multi-line string.
  Each line is preserved as-is.
  Great for scripts or SQL queries.

summary: >
  This text will be folded into
  a single line when parsed.

Anchors and aliases

YAML anchors (&) reuse values — avoids repetitiondefaults: &defaults
  retries: 3
  timeout: 30

production:
  <<: *defaults   # inherits retries and timeout
  timeout: 60     # overrides just this value

When to use each