About the YAML Formatter
What is a YAML formatter?
YAML runs half the modern toolchain — CI pipelines, Kubernetes manifests, Docker Compose files, app configs — and it is notoriously picky about indentation. This tool parses your YAML with the same battle-tested library most JavaScript tooling uses (js-yaml, bundled locally), then re-emits it with clean, consistent structure: your chosen indent width, normalized flow-style collections expanded into readable block style, and optional alphabetical key sorting.
Because every keystroke is genuinely parsed, you also get real validation: a mistake shows a red badge with the exact line and column, which is exactly what you need when a pipeline rejects your config. Multi-document files separated by --- are fully supported. One honest caveat inherent to parse-and-re-emit formatting: comments and anchor names are not preserved — the data always is.
How to Use This Tool
- Add your YAML. Paste it, open a
.yaml/.ymlfile, or click Sample. - Read the badge. Green means it parses (with a document count for multi-doc files); red shows the error with line and column.
- Shape the output. Choose 2- or 4-space indentation and optionally sort keys for diff-stable configs.
- Take the result. Copy it or download it as a
.yamlfile.
Common Use Cases
- Debugging CI configs: Find the exact line where your GitHub Actions or GitLab CI file breaks.
- Normalizing manifests: Bring Kubernetes and Compose files to consistent indentation and key order.
- Expanding compact YAML: Inline flow collections like
{a: 1, b: 2}become readable block style. - Validating before deploy: Catch tab characters, bad nesting, and duplicate keys before the server does.
- Cleaning exports: Tidy YAML produced by tools and generators.
Converting instead? Try YAML to JSON or JSON to YAML, or reorder documents with the YAML Sorter.
Frequently Asked Questions
How does the validation work?
Your document is parsed with js-yaml, the de facto standard YAML parser for JavaScript. If parsing fails, the exact line and column from the parser is shown in the red badge along with the reason — unclosed bracket, bad indentation, unexpected character, and so on.
Are comments preserved?
No — and this is true of any formatter that parses and re-emits YAML rather than editing text in place. Comments and anchor names are dropped; the data itself, including multi-document structure, is preserved exactly. If your file is comment-heavy, format a copy.
Does it support multiple documents in one file?
Yes. Files with several documents separated by --- are parsed and formatted document by document, and the green badge shows the count.
What happens to anchors and aliases?
They are resolved during parsing, so aliased content appears expanded (or re-anchored with generated names when shared). The resulting YAML is semantically identical even though the anchor names differ.
Why does my YAML fail with a tab error?
The YAML specification forbids tabs for indentation — only spaces are allowed. This is one of the most common reasons configs are rejected, and the badge points you at the exact offending line.
Is my YAML private?
Yes. Parsing and formatting run locally in your browser with the bundled library — no CDN, no uploads, no logging — and the tool works offline once loaded.