Three simple steps
- Paste YAML or load a UTF-8 .yaml or .yml file.
- Choose two-space or four-space indentation and format the document.
- Review the valid YAML, then copy or download it.
YAML Formatter & Validator
Format YAML with consistent indentation, validate its syntax, and keep comments in the result.
Validate YAML syntax
Preserve comments
Copy or download YAML
YAML input
Paste YAML or drop a UTF-8 .yaml or .yml file.
YAML result
Valid consistently formatted YAML appears here.
Document Tools guide
How to use YAML Formatter
Clean up configuration and data files while catching YAML syntax errors before using them in another system.
YAML handling
- Comments and document structure are retained by the YAML parser and serializer.
- Duplicate mapping keys are rejected to avoid silently replacing a value.
- Tabs used as YAML indentation and other syntax problems are reported with a location when available.
Frequently asked questions
Are YAML comments preserved?
Yes. Comments attached to the parsed YAML document are retained in the formatted output.
Does the formatter accept duplicate keys?
No. Duplicate mapping keys are reported as invalid because different YAML consumers may interpret them inconsistently.
Can I use either .yaml or .yml files?
Yes. Both UTF-8 file extensions are accepted.