YAML Formatter

What the formatter changes

• Indentation is normalized to 2 or 4 spaces at every level, including list items nested inside mappings.
• Flow style collections such as [a, b] and {k: v} are expanded into block style.
• Quoting is minimized: strings are left bare when safe and double-quoted only when needed to preserve their type or special characters.
• Trailing whitespace and inconsistent blank lines are removed.
• Multi-document streams are kept, with each document separated by ---.
• Key order is preserved unless you choose to sort keys.

Example

Input:

app:   { name: yamlchecker,   version: '2.1.0' }
server:
    host:    0.0.0.0
    port: 8080
features: [validator, formatter]

Output with 2-space indent:

app:
  name: yamlchecker
  version: "2.1.0"
server:
  host: 0.0.0.0
  port: 8080
features:
  - validator
  - formatter

When to use a YAML formatter

Formatting is most useful right before a code review or a commit. A consistent layout makes diffs smaller and easier to read, and running the file through a parser catches the indentation slips that YAML is famous for. If you only need to know whether a file is valid, the plain YAML validator is faster. To see how two versions of a file differ after formatting, use the YAML diff tool.