JSON vs YAML: When to Use Each

JSON and YAML can represent the same data — objects, arrays, strings, numbers, booleans — but they feel completely different to write. Knowing the trade-offs (and YAML's famous traps) helps you pick the right one and avoid painful bugs.

The quick comparison

• JSON — braces and brackets, strict, no comments, ubiquitous in APIs.
• YAML — indentation-based, human-friendly, allows comments, common in config.

In fact, any valid JSON is also valid YAML (for YAML 1.2), because YAML is a superset. That's why converting between them is usually painless.

Readability vs strictness

JSON's explicit punctuation makes it unambiguous and easy for machines, but noisy for humans — all those quotes, braces and commas. YAML drops most of that, using indentation to show structure, which reads cleanly for nested config. The flip side: YAML's whitespace is significant, so a misplaced space changes meaning, and that flexibility opens the door to surprises.

Comments and data exchange

A practical difference: YAML supports comments (lines starting with #); JSON does not. That alone makes YAML attractive for configuration files people edit by hand. JSON, being strict and universal, dominates machine-to-machine data exchange — almost every web API speaks JSON. Note that converting YAML to JSON drops the comments, since JSON has nowhere to put them.

YAML's famous traps

• The "Norway problem". Unquoted no, yes, on and off can be parsed as booleans. The country code for Norway, NO, may silently become false. When in doubt, quote your strings.
• Tabs. YAML forbids tabs for indentation — use spaces. Mixing them is a common parse error.
• Accidental numbers. A value like 1.10 or a version string may be read as a number and lose trailing zeros. Quote version strings.

Which should you use?

Use JSON for APIs and any data passed between programs — it's strict, universal and unambiguous. Use YAML for configuration that humans read and edit (Kubernetes manifests, CI pipelines, app config), where comments and readability pay off. Many ecosystems standardise on one; follow the convention of the tool you're configuring.

Try it

Convert between the two — and surface parse errors — with our YAML ↔ JSON converter. Tidy up JSON with the JSON formatter, and move tabular data with the JSON ↔ CSV converter.