What is YAML Formatter?
The YAML Formatter validates and pretty-prints YAML and can export the equivalent JSON. YAML is a human-friendly data serialization language; this tool follows the YAML 1.2 data model using the js-yaml library, which is widely used for parsing Docker Compose files, Kubernetes manifests, and CI configuration.
Paste YAML and the tool parses it, reports any syntax error, and re-emits a clean, consistently indented document. Because YAML is a superset of JSON's data model, it can also present your data as formatted JSON.
All parsing happens in your browser; your configuration is not uploaded.
Why Use This Tool?
YAML's significance of indentation makes it easy to introduce subtle structural errors. Validating and reformatting normalizes indentation and surfaces parse errors, so a misaligned key does not silently change your configuration's meaning.
- Catch indentation and syntax errors early.
- Normalize messy YAML into consistent formatting.
- Convert YAML to JSON for tools that need it.
- Clean up manifests and Compose files privately.
How Does This Tool Work?
The tool loads your YAML into an in-memory data structure with js-yaml, then dumps it back out with fixed options: two-space indentation, a 100-character line width, key order preserved, and references expanded (noRefs) so the output has no anchors or aliases. It also serializes the same structure as pretty-printed JSON.
If the document cannot be parsed, the library's error message — including the location — is shown so you can fix the offending line.
Understanding Your Results
A successful result gives you reformatted YAML and a JSON equivalent. Because the JSON view reflects the parsed data model, it is a reliable way to see exactly how the YAML will be interpreted — including how types like booleans, numbers, and null are resolved.
An error means invalid YAML: common causes are tabs used for indentation (YAML forbids tabs), inconsistent spacing, or a value that needs quoting. The noRefs dump means any anchors and aliases in your input are materialized into concrete values in the output.
Why Tracking This Matters
YAML configures much of modern infrastructure. A single indentation mistake can deploy the wrong settings, so validating and normalizing before applying changes prevents costly misconfiguration in CI/CD and orchestration.
Benefits of Using YAML Formatter
- YAML 1.2 validation via js-yaml
- Consistent two-space indentation
- JSON export of the parsed data
- Anchors and aliases expanded for portability
- Preserves original key order
- Runs entirely in your browser
How Is the Result Calculated?
There is no numeric calculation. The tool performs load (parse) then dump (serialize) with js-yaml using indent 2, lineWidth 100, noRefs true, and sortKeys false. The JSON export is JSON.stringify of the same parsed structure with two-space indentation.
Tips for Better Results
- Never use tabs for indentation — YAML requires spaces.
- Quote strings that could be misread as booleans, numbers, or null (for example, yes or 08).
- Use the JSON output to confirm how your types were resolved.
- Keep indentation consistent; the formatter normalizes it to two spaces.
- Expect anchors and aliases to be expanded in the output.
Standards and References
Conclusion
The YAML Formatter validates YAML against the 1.2 data model, normalizes indentation, and can export clean JSON, using the well-known js-yaml library.
Use it to catch indentation mistakes and confirm how your configuration will be interpreted before you deploy it.