Comparison1 min readUpdated June 29, 2026

YAML vs JSON: when to use each

Short answer

Use JSON for data exchanged between programs, especially APIs, because it is strict and universally supported. Use YAML for configuration that people edit by hand, because it is less noisy and supports comments. They can represent the same data.

Same data, different style

YAML is actually a superset of JSON, so any JSON document is valid YAML. The difference is ergonomics: JSON uses braces, brackets, and quotes; YAML uses indentation and is lighter to read and write.

JSON:                      YAML:
{                          name: Ada
  "name": "Ada",           roles:
  "roles": ["author"]        - author

The same data in JSON and YAML

What YAML adds

Comments with #, which JSON does not support
Less punctuation, so configuration is easier to scan
Anchors and references to reuse repeated blocks

Where YAML bites

Indentation is significant, so a stray space can change the meaning
Some unquoted values are surprising, for example a bare no can be read as false
It is harder for machines to parse quickly and consistently than JSON

Rule of thumbHumans edit YAML, machines exchange JSON. Many tools let you write YAML config and convert it to JSON at build time.

Try it: YAML to JSONConvert YAML configuration into formatted JSON locally in your browser.Open tool

References

Questions

Is every JSON file valid YAML?

Yes. YAML 1.2 is a superset of JSON, so a valid JSON document is also valid YAML. The reverse is not true, because YAML has features JSON lacks.

Why does YAML treat some words as booleans?

Older YAML parsers interpret bare words like yes, no, on, and off as booleans. Quote such values when you mean them as text to avoid surprises.

Does this send my data anywhere?

No. Utilumo's developer tools parse and transform input inside the browser tab. Nothing is uploaded, stored, or logged.