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YAML Formatter & Validator

Format and validate YAML, and convert between YAML and JSON both ways. Catches indentation and syntax errors. Runs in your browser. Free.

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💡 How to use

  • Format / validate re-indents your YAML with 2 spaces and reports syntax errors.
  • YAML → JSON and JSON → YAML convert between the two formats.
  • Supports maps, nested maps, sequences, lists of objects, inline flow, and quoted scalars. Runs in your browser — nothing is uploaded.

Free YAML Formatter, Validator & JSON Converter

Format, validate, and convert YAML instantly in your browser. Re-indent messy YAML with clean 2-space spacing, catch syntax errors, and convert between YAML and JSON both ways. Free, no sign-up, and nothing is uploaded.

What this tool does

YAML powers config files for tools like Docker Compose, Kubernetes, CI pipelines, and countless app settings — and its whitespace-sensitive syntax makes small mistakes easy to miss. This tool parses your YAML, tells you whether it is valid, re-formats it with consistent indentation, and converts it to and from JSON so you can work in whichever format you prefer.

How to use it

It is instant:

  • Paste YAML (or JSON) into the input box.
  • Choose a mode: format/validate, YAML → JSON, or JSON → YAML.
  • Click Run to see the result and a validity status.
  • Copy the clean output.

Validation that catches real mistakes

Because YAML uses indentation for structure, the most common errors are a stray tab, an inconsistent indent, or a missing colon. The validator parses your document and reports the specific problem — for example a tab used for indentation or a line that is not a valid key/value pair — so you can fix config files before they break a deployment.

YAML and JSON, both directions

YAML and JSON describe the same kind of data, so converting between them is common: you might turn a JSON API response into readable YAML for a config, or convert a YAML file into JSON for a script. This tool handles maps, nested maps, sequences, lists of objects, inline flow collections like <code>[1, 2, 3]</code> and <code>{a: 1}</code>, and quoted strings — reliably in both directions.

Common uses

Developers and DevOps engineers use a YAML formatter to tidy Docker Compose, Kubernetes manifests, GitHub Actions workflows, and application config; to validate a file after hand-editing; and to convert sample JSON into YAML (or the reverse) when writing documentation. Consistent formatting also makes YAML diffs in version control far easier to review.

Privacy

All parsing, formatting, and conversion run entirely in your browser — your YAML is never uploaded, logged, or stored. That matters for config files, which often contain hostnames, ports, and other infrastructure details you would not want to paste into a service that sends data to a server.

FAQ

Is this YAML tool free?
Yes. It is completely free, runs in your browser, and needs no account or sign-up.
Is my YAML uploaded?
No. Formatting, validation, and conversion all happen locally in your browser, so your data never leaves your device.
What errors does the validator catch?
Common structural problems such as tabs used for indentation, missing colons, and lines that are not valid key/value pairs, along with a message describing the issue.
Why does YAML forbid tabs?
The YAML spec requires spaces for indentation because tabs render inconsistently and would make structure ambiguous. The tool flags any tab used for indentation.
Can it convert YAML to JSON and back?
Yes. It converts YAML to JSON and JSON to YAML, handling maps, sequences, lists of objects, inline flow collections, and quoted scalars.
Does it support anchors and complex YAML features?
It targets the common subset used in real config files — maps, sequences, scalars, inline flow, and block scalars. Advanced features like anchors and custom tags are uncommon in everyday configs and are not the focus.
Will formatting change my data?
No. Formatting only normalizes indentation and quoting; the underlying keys, values, and structure stay the same.

Related tools

Pro tip: pair this tool with Upside Down Text Generator and What is My Browser for a faster SEO workflow.