Free Online YAML Validator
Instantly validate your YAML files for syntax errors and structural issues. Our free tool provides clear, line-by-line feedback to ensure your configuration files are correct and ready to use. No sign-up required.
YAML Validator
Validate YAML syntax and check for common errors
YAML Validation Rules
- Use spaces for indentation (not tabs)
- Key-value pairs use colon followed by space:
key: value - List items start with dash and space:
- item - Strings can be quoted or unquoted
- Comments start with hash:
# comment - Ensure proper indentation for nested structures
How it works
Paste your YAML content into the editor. The validator parses the content and checks for syntax errors, indentation issues, and structural problems. Results appear instantly as you type.
Error messages indicate the exact line and column where problems occur. Common issues include incorrect indentation, missing colons, invalid characters, and malformed structures.
Validation example:
Invalid YAML: name: John age: 30 # Wrong indentation Error: Line 2, Column 3 Bad indentation: expected 0 spaces
The validator supports YAML 1.2 specification including anchors, aliases, and multi-document streams. Large files process efficiently with helpful error localization.
When You'd Actually Use This
CI/CD pipeline debugging
GitHub Actions YAML failing? Validate before commit. Catch syntax errors early. Fix workflow issues quickly.
Kubernetes manifest validation
Verify deployment configs. Catch YAML errors before kubectl apply. Prevent cluster issues. Ensure valid manifests.
Docker Compose files
Validate compose.yaml syntax. Check service definitions. Verify volume mounts. Prevent container startup failures.
Configuration file editing
Ansible playbooks, Helm charts. Any YAML config benefits. Catch typos and formatting. Ensure valid syntax.
API response debugging
Validate YAML API responses. Check webhook payloads. Debug integration issues. Verify data structures.
Learning YAML syntax
Students learning configuration. Practice YAML formatting. Get instant feedback. Build correct habits.
What to Know Before Using
Indentation must be consistent.YAML uses spaces, not tabs. Mixing causes errors. Standard is 2 spaces per level. Be consistent throughout file.
Colons need space after.key: value not key:value. Space after colon is required. Exception: empty values allowed. Common source of errors.
Strings may need quotes.Special characters require quoting. Booleans and numbers as strings need quotes. When in doubt, quote it.
Comments start with hash.# begins a comment line. Inline comments after values. Don't put comments inside strings. Can cause parse errors.
Pro tip: Use a YAML-aware editor with linting. VS Code, Sublime, Atom have extensions. Catch errors as you type, not after.
Common Questions
What's the most common YAML error?
Indentation errors. Mixing tabs and spaces. Inconsistent indentation levels. Always use spaces, be consistent.
Does this support YAML anchors?
Yes, anchors (&) and aliases (*) are valid YAML. Validator checks their proper usage. References must point to defined anchors.
Can it validate multi-document YAML?
Yes, documents separated by ---. Each validates independently. Errors show per document. Useful for Helm charts.
How large a file can I validate?
Browser handles moderate files well. Very large files may be slow. Split huge configs if needed. Most configs are small.
Does it check semantic validity?
Syntax only, not semantics. Valid YAML may not be valid for your app. Schema validation is separate concern.
Can I validate JSON with this?
JSON is valid YAML subset. Works for JSON too. But use JSON validator for JSON-specific errors. Better error messages.
Is my data sent to a server?
No, validation happens in browser. Your YAML never leaves your computer. Safe for sensitive configurations. Client-side only.
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