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.

Frequently Asked Questions

What is the main difference between JSON and YAML?

JSON uses braces and brackets with strict quoting rules, making it unambiguous and fast to parse. YAML uses indentation instead of delimiters and supports comments, making it more human-readable but slower to parse and prone to subtle whitespace bugs.

Which is better for configuration files, JSON or YAML?

YAML is generally better for configuration files because it supports comments (letting you document why a setting exists), is easier to read and edit by hand, and handles multi-line strings cleanly. JSON is better when the configuration is machine-generated or consumed primarily by APIs.

Can JSON have comments?

Standard JSON (RFC 8259) does not support comments. Some tools like JSON5 and JSONC extend JSON to allow comments, but these are not universally supported. If you need comments in your data format, use YAML, TOML, or a JSON superset.

Is YAML a superset of JSON?

YAML 1.2 is designed to be a superset of JSON, meaning any valid JSON document should also be valid YAML. However, there are edge cases where this breaks in practice, particularly around special characters and certain number formats. Do not rely on this for production code.