YAML Formatter and Syntax Checker
Validate and format YAML or convert it to readable JSON for configuration, documentation, and debugging.
About this tool
YAML is readable configuration syntax, but indentation, quoting, and collection errors can be difficult to spot. This tool uses a maintained YAML parser to check nested mappings, lists, block strings, anchors, aliases, numbers, booleans, and null values. Parsing and formatting happen locally in the browser.
How to use it
- Paste YAML with spaces used consistently for indentation.
- Select Format / Check YAML to validate and normalize the layout, or Convert to JSON for a JSON representation.
- Read any line-and-column error, correct the input, and run the action again.
- Compare strings, dates, numbers, booleans, anchors, and aliases before using the output in production.
Tips and common mistakes
- Keep indentation consistent because YAML uses spacing to describe structure.
- Quote values that resemble dates, codes, or version numbers when they must remain strings.
- Formatting rebuilds the document from parsed data, so comments and some original style choices are not preserved.
- Aliases are resolved when converting to JSON; review the expanded result carefully.
FAQ
Will formatting preserve comments?
No. The formatter parses and serializes the data, so comments and original spacing are removed. Keep the original file or use a comment-preserving editor when comments matter.
Why did my value become a number?
Unquoted numeric values are parsed as numbers. Add quotes if the value must remain text.
Is my configuration uploaded?
No. Parsing and conversion run in this browser page.
Related tools
Related guides
YAML vs JSON: differences and uses and How to convert YAML to JSON online.
Related tools and guides
- Format YAML before converting — Validate indentation and readability first.