What is the YAML Norway problem?

In YAML, "NO" and "NO" were parsed as false (boolean) in YAML 1.1 — affecting Norway's country code "NO". YAML 1.2 fixed this — only "true" and "false" are booleans. However, many YAML parsers still use 1.1 rules. Always quote values like "NO", "yes", "on", "off" in YAML.

Can I add comments to JSON?

Standard JSON does not support comments. Workarounds: use JSONC (JSON with Comments, supported by VS Code), use JSON5 (extends JSON with comments and trailing commas), or add a "_comment" key (hacky). For config files needing comments, use YAML or TOML instead.

Is YAML faster or slower than JSON?

JSON is significantly faster to parse — it has a simple grammar and built-in browser/language support. YAML parsing is slower due to indentation tracking, implicit type detection, and complex anchors/aliases. For performance-critical data exchange, always use JSON (or protobuf for binary).

Last updated: April 7, 2026

YAML vs JSON — Which Format Should You Use?

Quick Answer

Use JSON for API data exchange, JavaScript config files (package.json), and machine-generated data. Use YAML for configuration files that humans write and maintain (Docker Compose, Kubernetes, GitHub Actions, Ansible). YAML is a superset of JSON — all valid JSON is valid YAML.

YAML vs JSON — Side by Side

Feature	YAML	JSON
Human readability	Excellent — indent-based, no brackets	Good — explicit structure
Supports comments	Yes — # comment	No
Verbosity	Less verbose	More verbose (quotes, brackets)
Parsing complexity	High (indentation, implicit types)	Low (explicit, well-defined)
Gotchas	Yes (true/false/null/on/off ambiguity)	Fewer gotchas
Common use	Docker, Kubernetes, GitHub Actions, Ansible	REST APIs, package.json, data storage
Browser support	No native parser	JSON.parse() built-in
Speed	Slower to parse	Faster to parse

Verdict

YAML for human-maintained config files where readability and comments matter. JSON for machine-generated data, APIs, and JavaScript ecosystems. Never use YAML where strict parsing is critical (YAML's implicit type conversions like Norway problem are notorious footguns).

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