JSON vs YAML: When to Use Which

JSON and YAML are the two dominant data serialization formats in modern software. JSON rules the web. YAML rules DevOps. But they overlap, and choosing between them matters.

Syntax comparison

The same data, two ways:

JSON:

{
  "name": "anan.zh.kg",
  "version": 1,
  "tools": ["uuid", "base64", "json"],
  "active": true,
  "maintainer": {
    "name": "deng",
    "email": "hi@anan.zh.kg"
  }
}

YAML:

name: anan.zh.kg
version: 1
tools:
  - uuid
  - base64
  - json
active: true
maintainer:
  name: deng
  email: hi@anan.zh.kg

When to use JSON

• APIs and web services — universal browser and language support
• Data interchange — the lingua franca of HTTP, message queues, and storage
• Schemas — paired with JSON Schema for validation
• When speed matters — JSON parsers are 5-10x faster than YAML parsers

When to use YAML

• Configuration files — Kubernetes, GitHub Actions, Ansible, Docker Compose, CI pipelines
• Human-edited data — comments, multi-line strings, anchors are YAML strengths
• Documentation — OpenAPI specs, Swagger, Postman exports
• When readability matters more than speed

YAML features JSON cannot match

• Comments — # this is a comment
• Anchors and aliases — DRY: &anchor *ref
• Multi-line strings — | literal, > folded
• References to other documents — multi-file configs
• No quotes required — cleaner for most strings

JSON features YAML cannot match

• Speed — JSON is 5-10x faster to parse and serialize
• Strictness — no Norway problem, no truthy string surprises
• Universal support — every language, every browser, every tool
• Smaller output — 10-30% less whitespace

The Norway problem

YAML 1.1 had a notorious surprise: no is parsed as boolean false. So country: Norway became {country: false}. YAML 1.2 (2009) fixed this, but many parsers default to 1.1 for compatibility. Always quote your strings when in doubt: country: "Norway". See the official YAML 1.2 spec for details.

Practical advice

Use JSON for any data that crosses a network boundary or is consumed by a program.

Use YAML for configuration files written and maintained by humans.

If you need both, the YAML spec has a !!json tag to embed JSON inline, and most JSON files are valid YAML (with caveats around comments and strictness).

Format your JSON with our JSON Formatter.