Does the YAML get uploaded?

No. Parsing and serialisation happen in your browser. You can safely format files that contain secrets or internal config.

Will comments survive a round trip?

Yes. Line and trailing comments are preserved next to the keys they annotate, including comments inside flow sequences.

How are anchors and aliases handled?

&anchor and *alias references are kept intact and re-emitted on the same nodes. Merge keys (<<:) are also preserved.

Does it support multi-document YAML streams?

Yes. Documents separated by --- are each parsed and re-emitted, and the separator is retained between them.

prettier · yaml · live · client-side

Format YAML with Prettier

Q: Does it support multi-document YAML streams?

Yes. Documents separated by --- are each parsed and re-emitted, and the separator is retained between them.

Prettier's yaml printer re-indents documents, normalises flow vs block style, and fixes the mixed-spacing chaos that breeds in long CI files. Runs locally.

YAML Formatter

Input

122 B

11 lines

Output

0 B

1 lines

Status

parser…

Ratio

0.00×

out/in

input · yaml

output · formatted yaml

Loading parser…

Quick Start

How to format YAML

Prettier's yaml plugin parses the document, normalises indentation, and re-emits with consistent block style. Multi-document files are preserved.

01
Paste a YAML file
docker-compose.yml, GitHub Actions workflow, Kubernetes manifest, any YAML.
Parsing runs through Prettier’s standalone bundle (or the language-specific equivalent) loaded lazily — no parser ships until the tool is opened.
yamlPrettierASTstandalonelazy
input · sourceraw · AST
```
name: x
port: 80
```
loaded · parsedAST · ready
02
Pick width
Tab controls indent; print width forces long flow sequences to wrap into block form.
Indent width, tab style, and print-width re-format through a memoised pass — switching 2 → 4 spaces never re-parses, only re-prints.
optsindentprint-widthmemoisedlive
opts · optionstab/width · live
```
tab=2
width=80
```
options applied · livelive
03
Indents canonical
Mixed tabs/spaces become tabs of N; flow lists [a,b,c] may switch to block based on width.
The formatter is deterministic and idempotent: running it twice produces byte-identical output, which keeps diffs and git noise to a minimum.
liveidempotentdeterministicdiff-cleanstable
out · formattedpretty · ready
```
items:
  - a
  - b
```
formatted · liveidempotent
04
Copy or save
Drop into your repo or CI config. Source never leaves your tab.
Download writes a Blob with the language-appropriate extension; copy uses navigator.clipboard.writeText so the output preserves all whitespace exactly.
exportclipboardbloblanguage MIMEclient-side
ok · copiedready · done
```
✓ Copied
```
shipped · ready to shipsuccess

Pro tips

Formatting tips that keep diffs sane

Pick one config and pin it

Inconsistent formatting causes diff churn. Commit .prettierrc / .editorconfig and enforce in CI.

Format on save

Editor integration is faster feedback than a pre-commit hook. Use both for belt-and-braces.

Idempotency matters

Running the formatter twice should produce identical output. Test this on a representative file.

Match the language community

Default to community conventions: 2 spaces for JS/CSS, 4 for Python, tabs for Go. Fights over indent are a productivity tax.

Print-width drives wrapping

80, 100, and 120 are the common targets. Wider lines parse fast but review slower side-by-side.

Don’t mix formatters and linters

Prettier handles whitespace; ESLint handles correctness. Disable overlapping rules to avoid fight-club configs.

Use Cases

When to format YAML

CI files, k8s manifests, config sprawl.

CI workflows

Tidy a GitHub Actions or GitLab CI yml after edits. Idempotent: running the formatter twice produces byte-identical output, which is the foundation of a clean CI gate. Pair with a pre-commit hook so PRs arrive already formatted, focusing review on logic.

idempotent

Kubernetes

Standardise indentation across many manifests. Pairs with EditorConfig + .prettierrc for end-to-end consistency. Whitespace-only changes vanish so reviewers see real diffs, and git blame stays honest about who wrote what.

k8s

Helm values

Format values.yaml after a chart bump. Output respects your indent width, tab style, and print-width — settings carry over for repeat runs. Switching 2-space to 4-space costs nothing in CPU but standardises an entire codebase.

diff-clean

OpenAPI

Format OpenAPI specs before checking into source control. Format-on-save is the fastest feedback loop; CI is the safety net. Together they make inconsistent indentation a thing of the past and free up review cycles for genuine concerns.

PR-friendly

Code review

Whitespace-only diffs disappear when both sides are canonical. Whitespace-only changes don't trigger downstream content-hash invalidations, so CDN cache keys and CI cache layers stay warm. Real changes get all the rebuild budget.

review-ready

Multi-document

Format files with --- separators preserving each doc. Pairs with linters (ESLint, Stylelint, pylint) that catch what formatting alone can't — bugs, unused imports, dead code. Each tool stays in its lane, and the codebase stays clean.

deterministic

FAQ

Frequently asked questions

Does it preserve comments?

Yes — Prettier's yaml plugin keeps # comments on their original lines.

What about anchors and aliases?

Preserved verbatim. Prettier doesn't expand them.

Will it change block vs flow style?

Yes — long flow sequences may switch to block form when print width forces a wrap.

Multi-document support?

Files with --- separators are formatted one document at a time and rejoined.

Is anything sent to a server?

No — Prettier runs locally in your browser tab.

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