What YAML features are supported?

Mappings, sequences, comments, quoted and plain scalars, numbers, booleans, null, inline arrays and objects, and literal or folded block scalars are supported. Anchors, aliases, tags and multi-document files are reported as unsupported.

Does formatting keep my comments?

No. The formatter parses the document and writes a clean canonical version, so comments are removed. Keep the original if the comments matter, or copy the formatted output into a new file.

Why does indentation matter in YAML?

YAML uses indentation to express nesting. Tabs are not allowed, and each nested level must be indented further than its parent. The validator points out the first problem it finds.

No. Parsing, validation and formatting run entirely in your browser. Nothing is stored or sent to a server.

YAML Formatter & Validator

Clean up indentation, normalise spacing and validate YAML before it reaches your pipeline. See the result as YAML or JSON. Everything runs in your browser.

YAML input0 characters

Tabs, bad indentation, duplicate keys and unterminated quotes are reported with line numbers.

Formatted YAML

Valid YAML will appear here…

What the formatter does

Re-emits mappings and sequences with consistent indentation and one space after each colon.
Recognises strings, quoted strings, integers, decimals, booleans and null.
Supports inline arrays and objects plus literal (|) and folded (>) block scalars.
Quotes values that would otherwise be read as numbers, booleans or null.
Removes comments — formatting is a rewrite, not a whitespace-only pass.
Reports anchors, aliases, tags and multiple documents as unsupported rather than guessing.

Converting to or from JSON? Use the JSON ↔ YAML / CSV Converter or check the result with the JSON Formatter.

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Runs in your browser — nothing is uploaded.

YAML Formatter & Validator

What the formatter does

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