YAML and JSON represent the same data structures. Both support strings, numbers, booleans, arrays, and nested objects. Both are widely used for configuration and data interchange. So when should you choose one over the other?
The Key Difference
YAML is a superset of JSON — valid JSON is valid YAML. But YAML's syntax is designed for human readability while JSON's is designed for machine parsing.
JSON:
`<code>json</p>
<p>{</p>
<p>"name": "app",</p>
<p>"version": "1.0",</p>
<p>"features": ["fast", "free"],</p>
<p>"config": {</p>
<p>"maxRetries": 3,</p>
<p>"timeout": 30</p>
<p>}</p>
<p>}</p>
</code>
Same data in YAML:
<code>yaml
<p>name: app</p>
<p>version: "1.0"</p>
<p>features:</p>
<p>- fast</p>
<p>- free</p>
<p>config:</p>
<p>maxRetries: 3</p>
<p>timeout: 30</p>
</code>
The YAML version has no curly braces, no commas, and no quotes unless necessary.
When to Use JSON
- REST APIs and HTTP responses — JSON is the standard. All HTTP clients handle it natively.
- Data interchange between systems — Every language has a fast, well-tested JSON parser.
- Machine-generated files — package-lock.json, composer.lock, database exports.
When to Use YAML
- Configuration files — Kubernetes manifests, Docker Compose, GitHub Actions, Ansible playbooks. Written and edited by humans frequently.
- Multi-line strings — YAML block scalars handle multi-line strings elegantly. JSON requires \n
escape sequences. - When you need comments — YAML supports #
comments. JSON does not. Being able to explain why a setting exists is invaluable in config files.
YAML Gotchas
The Norway Problem — YAML 1.1 interprets bare NO, N, Off, False as boolean false. Country code NO (Norway) gets silently converted to false. Quote values that look like keywords.
Implicit type coercion — version: 1.0 becomes a float. port: 8080` becomes an integer. Add quotes when you need a string.
Tabs vs spaces — YAML forbids tabs for indentation. Spaces only.
Quick Decision Guide
| Situation | Use |
|-----------|-----|
| REST API response | JSON |
| GitHub Actions / CI config | YAML |
| Kubernetes manifest | YAML |
| npm package.json | JSON |
| Docker Compose | YAML |
| Database export | JSON |
| Human-edited config | YAML |
| Machine-generated data | JSON |
The general rule: YAML for humans writing configuration, JSON for machines exchanging data.
Converting Between Them
The YAML ↔ JSON Converter at SnappyTools handles both directions instantly in the browser — paste JSON to get YAML, paste YAML to get JSON. No account required.
Originally published at https://snappytools.app/yaml-json-converter/