YAML Formatter

What this tool does

Paste messy, inconsistently-indented, or minified YAML and get it back cleanly reindented and normalized. Choose how many spaces to indent per nesting level, alphabetize every mapping's keys, or collapse the whole document to compact flow style. It parses the YAML, so invalid input is reported as an error instead of being silently mangled.

Everything runs locally in your browser via WebAssembly — your YAML never leaves your machine and there are no network requests.

Options

• Spaces per level — indentation width for block style, from 1 to 8 (default 2). YAML forbids tab characters for indentation, so only spaces are offered.
• Output style
  • block — expanded, multi-line YAML (the usual, readable layout).
  • flow — compact, single-line JSON-like YAML ({name: gizza, tags: [a, b]}), handy for minifying or embedding a value on one line.
• Key order
  • preserve — keep the original key order (default).
  • asc / desc — sort every mapping's keys alphabetically, recursively — useful for producing diff-stable config files.

Worked example

Input (inconsistent spacing and inline collections):

name:   gizza
tags: [a, b]
nested: {x: 1}

Style block · Indent 2 spaces · Key order preserve

Output:

name: gizza
tags:
  - a
  - b
nested:
  x: 1

Switch Output style to flow to get {name: gizza, tags: [a, b], nested: {x: 1}} on a single line, raise Spaces per level to 4 to widen the indentation, or set Key order to asc to alphabetize the keys.

Limits and edge cases

• This is a formatter, not a linter or schema validator — it checks that the YAML parses and re-emits it, but it doesn't check your data against a schema.
• Comments, blank lines, and anchors are not preserved. The document is parsed into a data model and re-emitted, so # comments, spacing between blocks, and &anchor/*alias references are dropped — aliases are expanded to the value they point at.
• Strings that would otherwise be read back as a boolean, null, or number ("true", "null", "123") are double-quoted to keep their type. Other strings are left unquoted where that is unambiguous.
• Indentation is clamped to 1–8 spaces; tabs are not used (YAML forbids tab indentation).
• Multi-document streams separated by --- are supported; each document is normalized independently.
• To convert YAML to or from JSON/TOML instead of reformatting it, use a dedicated converter — this tool always outputs YAML.

FAQ