DEVELOPER TOOLS
YAML Formatter & Validator
Format or validate one YAML document, or convert between YAML and JSON. All processing happens in this browser; input is not sent or saved.
Maximum 100,000 characters. Empty input is not treated as a valid document.
Output is plain text. Review conversions, especially large values and aliases.
Enter YAML or JSON to begin.
How this YAML tool works
Format YAML preserves parsed comments, anchors, aliases, and multiline scalar styles where possible. It changes presentation and may normalize quoting or spacing. Validate checks syntax; it does not check an application schema or whether a configuration is meaningful to another program. JSON to YAML accepts standard JSON values, including objects, arrays, strings, numbers, booleans, and null.
This tool supports one YAML 1.2 document using the core schema. A single document may start with ---; a stream containing multiple documents is rejected. Empty input is reported separately, while an explicit empty document is treated as YAML null. Unsupported tags are rejected. Anchors and aliases are parsed locally; YAML-to-JSON limits alias expansion to 50 references, rejects circular aliases, and only accepts string mapping keys. Oversized integers that JSON cannot represent without loss are also rejected.
Input is limited to 100,000 characters. Processing uses the yaml JavaScript parser version 2.9.1 (ISC), bundled as a local browser asset. Conversions use JavaScript numbers, so very precise fractional values may be rounded; unsafe integers and non-finite JSON numbers are rejected. YAML behavior can vary across parsers and application schemas. This tool does not execute YAML tags or save or transmit your input.