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YAML Formatter & Validator — Reformat, Minify & Lint YAML

Validate, reformat, and minify YAML in your browser. Catches syntax errors with line numbers.

Free No signup Client-side Privacy friendly Updated

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How to use

  1. 1 Paste your YAML.
  2. 2 Pick Reformat for indented block style, Flow for compact JSON-like form.
  3. 3 Optionally sort keys for diff-friendly output.
  4. 4 Copy or download.

Why use this tool

  • Powered by js-yaml — round-trips your YAML through a real parser.
  • Validation catches syntax errors with parser messages.
  • Sort-keys mode is great for stable diff in version control.
  • Pure client-side, your config never uploads.

Frequently asked questions

Why does my anchor/alias get expanded?

YAML anchors (&) and aliases (*) are resolved on parse — the output represents the materialized data. If you need to preserve aliases as-is, do not reformat.

Will key order change?

No, unless you enable Sort keys. By default, the parser preserves order as written.

What about YAML 1.1 vs 1.2 quirks?

js-yaml uses YAML 1.2 semantics by default — "yes/no/on/off" are strings (not booleans). If your input depends on YAML 1.1, expect quoted-string output.

What is YAML Formatter & Validator?

A YAML Formatter is a tool that validates, reformats, and minifies YAML data. It checks the input for syntax errors and reports them with line numbers, re-indents valid documents into a consistent readable layout, and can compact them to reduce size. It runs entirely in the browser, processing YAML on the device without uploading it to a server.

Features

Validate

Parses input against the YAML 1.2 spec with js-yaml and flags syntax errors with the exact line.

Reformat & minify

Re-indent with 2- or 4-space block style, or compact to flow style to reduce size.

100% private

Runs entirely in your browser — your YAML is never uploaded.

Example

Input

{name: Zerethon, tools: [json, yaml], free: true}

Output

name: Zerethon
tools:
  - json
  - yaml
free: true

Common use cases

  1. 1

    Clean up CI & config files

    Normalize hand-edited GitHub Actions, Docker Compose, or Kubernetes YAML before committing.

  2. 2

    Catch indentation bugs

    YAML is whitespace-sensitive; validate to find the mis-indent that silently breaks a pipeline.

  3. 3

    Convert flow ↔ block

    Expand a compact flow-style document into readable block style, or the reverse.

How YAML Formatter & Validator compares to alternatives

YAML Formatter & Validator versus typical browser and desktop alternatives — features compared at a glance.
Feature Zerethon Tools Typical online tools Desktop apps
Signup required No Sometimes No (IDEs)
Data leaves device No Yes No
Validate + reformat + minify All three Sometimes Varies
Line-numbered errors Yes Sometimes Yes
Free Yes Yes Often paid
Works offline Yes (after load) No Yes
Summary

Zerethon's YAML formatter validates, reformats, and minifies YAML 1.2 in your browser using the js-yaml parser — a real YAML implementation, not string manipulation. Syntax errors are reported with line numbers; valid documents are re-indented consistently or compacted to flow style. Everything runs client-side, so your YAML is never uploaded.

Category
Developer
Pricing
Free
Privacy
Browser-based
Signup
Not required

References

Privacy

Your data never leaves your browser unless explicitly stated. YAML Formatter & Validator runs entirely client-side — no server upload, no logging, no tracking of your input.

Compare

JSON vs YAML YAML vs XML

Learn the basics

What is YAML?

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