JSON vs YAML: Which Should You Use?

Compare JSON and YAML for configuration files, API responses, and data interchange — with concrete rules for when each format is the right choice.

What They Have in Common

Both JSON and YAML represent structured data as key-value pairs, arrays, strings, numbers, booleans, and null. Any valid JSON document is also valid YAML — YAML is a superset of JSON. The differences are in syntax, readability, and ecosystem support.

JSON: Strict, Verbose, Universal

{
  "database": {
    "host": "localhost",
    "port": 5432
  },
  "features": ["auth", "billing"]
}

JSON requires quotes around all keys, commas between items, and has no comment syntax. This verbosity is also its strength: every JSON parser in every language produces the same result with no parsing surprises.

YAML: Readable but Fragile

database:
  host: localhost
  port: 5432
features:
  - auth
  - billing

YAML eliminates quotes and braces, replacing them with indentation. It supports comments with #, multi-line strings, and anchors for reusing values — making complex configuration files far more readable.

YAML Pitfalls

The Norway problem: country: NO is parsed as boolean false in YAML 1.1 parsers
Indentation sensitivity: Mixing tabs and spaces produces parse errors that are hard to debug
Implicit types: port: 5432 is an integer; enabled: yes is a boolean — all without quotes

When to Use Each

Use Case	Recommendation
API responses / requests	JSON — universal parser support
Config files humans edit	YAML — comments, readability
CI/CD pipelines (GitHub Actions)	YAML — industry standard
Kubernetes manifests	YAML — ecosystem default
Storing data in databases	JSON — easier to query with SQL JSON functions

Practical Rule

Use JSON when machines write and read the data. Use YAML when humans write and machines read it. The comment support in YAML is genuinely valuable for configuration files — being able to explain why a setting exists is worth the indentation trade-off.