YAML Validator + JSON Converter (Free, No Signup)

YAML Validation: The Most Common Pitfalls

YAML looks simple but bites in subtle ways. The 8 problems below account for most YAML bugs in CI/CD, Kubernetes manifests, and config files.

The Norway Problem (Boolean Coercion)

Unquoted NO is parsed as the boolean false. So country: NO becomes country: false. Same problem hits yes/no/on/off/true/false (and their case variants in YAML 1.1). Fix: quote string values that look like booleans — country: "NO".

Tabs vs Spaces

YAML forbids tabs for indentation. Most editors auto-fix this, but a stray tab from a paste will silently break parsing. Fix: configure your editor to expand tabs to 2 spaces (the standard for YAML).

Numeric Strings

version: 1.0 is parsed as the float 1.0, not the string "1.0". So version: 1.10 becomes 1.1 (trailing zero stripped). Fix: quote version numbers and other identifiers that look numeric — version: "1.10".

Multi-line Strings: | vs >

• | — literal block (preserves newlines exactly)
• > — folded block (newlines become spaces)
• |+ / >+ — keep trailing newlines
• |- / >- — strip trailing newlines

Other Gotchas

• Colons in values — url: http://example.com can confuse parsers. Quote it.
• Trailing whitespace — invisible but can break diffs and some parsers. Configure your editor to trim on save.
• Anchors and aliases (& / *) — powerful but hard to debug. Keep them simple or avoid for production config.
• Document separator — --- on its own line means a new YAML document. Easy to miss when concatenating files.

YAML to JSON (and Back)

YAML is a superset of JSON — every valid JSON document is valid YAML 1.2. Converting YAML → JSON is lossless. Converting JSON → YAML loses no data but can change formatting (comments are dropped, since JSON has none).