What this validates
The validator checks mappings, sequences, anchors, aliases, merge keys, block scalars, folded scalars, quoted values, unquoted values, indentation, and multiple YAML documents.
YAML Validator
Paste YAML to validate syntax, find parsing errors, and review helpful configuration warnings.
Paste YAML content or load a sample to begin.
YAML input
Paste configuration YAML, manifests, workflows, API descriptions, or multi-document files.
Validation report
Validate YAML to generate a report.
Ready to validate YAML
Paste YAML or load a sample to check syntax, indentation, duplicate keys, aliases, custom tags, and multi-document structure.
YAML Validation Guide
Validate YAML syntax before deployment
YAML Validator focuses on parser-safe checks for configuration text, not formatting or conversion.
YAML Validator vs YAML Formatter
YAML Validator reports syntax and structure issues without rewriting your file. YAML Formatter validates first, then produces normalized YAML output.
Common syntax errors
Misaligned sequence dashes, tabs for indentation, missing spaces after colons, unclosed quotes, unresolved aliases, and duplicate keys commonly break YAML consumers.
Indentation rules
YAML structure is controlled by spaces. Use consistent indentation and avoid tabs because many parsers reject or misread tab-indented configuration.
Anchors and aliases
Anchors, aliases, and merge keys can reduce repeated configuration, but downstream tools may resolve them differently or lose them during JSON conversion.
JSON compatibility
Custom tags, merge keys, aliases, comments, and multi-document streams are YAML features that may not map cleanly to JSON or schema-driven tools.
YAML Validator FAQ
Does this execute YAML tags, templates, scripts, or references?
No. YAML is treated as configuration text only. The validator does not execute tags, templates, scripts, shell expressions, or external references.
Does it support multiple YAML documents?
Yes. YAML streams with document separators are parsed as separate documents and included in the document count.
Why warn about duplicate keys?
Duplicate keys are risky because different YAML consumers may keep the first value, keep the last value, or reject the file.
Can valid YAML still have warnings?
Yes. The syntax may be valid while still containing tabs, duplicate keys, custom tags, merge keys, empty documents, or YAML-specific features that deserve review.
Is YAML Validator different from YAML to JSON?
Yes. YAML Validator checks YAML syntax and configuration risks. YAML to JSON converts parsed YAML data into JSON and can lose YAML-only syntax.