Will formatting remove my YAML comments?

The js-yaml library used for parsing does not preserve comments in its AST, so formatting via parse-and-reserialize loses comments. We preserve comments by using a whitespace-aware formatting pass that retains comment lines from the original. However, inline comments on the same line as a value may be repositioned.

Does the formatter work on Kubernetes multi-document YAML files (with --- separators)?

Yes. Multi-document YAML files are split at the --- separator, each document is formatted independently, and the results are rejoined with --- separators.

My YAML has anchors (&anchor) and aliases (*alias) — will those be preserved?

YAML anchors and aliases are resolved during parsing, producing the full dereferenced structure. When re-serialized, anchors and aliases may be eliminated (the value is simply repeated). If you need anchors preserved, use a YAML processor that maintains the anchor/alias structure like ruamel.yaml in Python.

YAML Formatter | DevStackTools

YAML Formatter & Prettifier — Beautify YAML Documents Online

Understanding the Basics

YAML formatting is more nuanced than JSON formatting because YAML offers multiple equivalent representations for the same data. Objects can be written in block style (indented key-value pairs on separate lines) or flow style (JSON-like curly braces on one line). Arrays can use block style (dash-prefixed lines) or flow style (square brackets). A well-formatted YAML document consistently uses block style for complex nested structures (improving readability) and flow style only for simple inline values. Inconsistent mixture of styles, excessive blank lines, inconsistent indentation depths, and trailing whitespace all make YAML files harder to maintain in version control and more prone to merge conflicts. YAML formatting is particularly important in Kubernetes and Helm chart repositories where dozens of developers collaborate on the same manifest files — a style-normalized formatter ensures that all contributors produce identical formatting regardless of their editor settings. Our formatter parses the YAML, normalizes the representation, and re-serializes it with consistent 2-space indentation and block-style output for all structures except simple inline values.

How to Use the Tool

Paste your YAML document into the input editor.
Click "Format" to normalize the document with consistent indentation and block style.
Flow-style objects ({key: value}) are expanded to block style for complex structures.
The output preserves all data values and comments (comments are maintained if present in input).
Download the formatted YAML or copy it for your config file, manifest, or playbook.

Key Features & Specifications

Normalizes mixed block and flow styles to consistent block-style formatting
Configurable indentation: 2-space (Kubernetes standard) or 4-space
Removes trailing whitespace and normalizes blank lines between sections
Preserves YAML comments during formatting
Validates YAML syntax before formatting to prevent corrupting invalid documents

Frequently Asked Questions (FAQ)

Q:Will formatting remove my YAML comments?: The js-yaml library used for parsing does not preserve comments in its AST, so formatting via parse-and-reserialize loses comments. We preserve comments by using a whitespace-aware formatting pass that retains comment lines from the original. However, inline comments on the same line as a value may be repositioned.
Q:Does the formatter work on Kubernetes multi-document YAML files (with --- separators)?: Yes. Multi-document YAML files are split at the --- separator, each document is formatted independently, and the results are rejoined with --- separators.
Q:My YAML has anchors (&anchor) and aliases (*alias) — will those be preserved?: YAML anchors and aliases are resolved during parsing, producing the full dereferenced structure. When re-serialized, anchors and aliases may be eliminated (the value is simply repeated). If you need anchors preserved, use a YAML processor that maintains the anchor/alias structure like ruamel.yaml in Python.