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YAML Validator

Make sure your YAML is valid before you deploy or share it. Upload or paste text, run validation, and see what needs fixing. Handy during debugging.

YAML Validator

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Result will appear here...

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Last updated: June 9, 2026

Created by: Eon Tools Dev Team

Reviewed by: Sugam Baskota


What this does

So a YAML file is about to break a deployment or a config load, and you want to catch the problem before it does. This checks it. Paste your YAML or upload a file, press Validate, and it tells you whether the YAML is valid, and if not, what went wrong.

How to use it

  1. Paste your YAML, or upload a .yaml file.
  2. Press Validate.
  3. Read the result: either it confirms the YAML is valid, or it shows the error.

How it works

The check is done by js-yaml, a widely used YAML parser. It tries to load your YAML as data, and if it cannot, it reports the error, usually pointing to the line where the trouble is. If it loads without complaint, your YAML is valid. The whole thing runs in your browser, so your file is not uploaded anywhere.

What usually breaks YAML

YAML has a few habits that catch people out, and they are behind most of the errors you will see. Indentation has to be consistent and made of spaces, never tabs, since YAML flatly rejects tabs for indentation. A colon needs a space after it when it separates a key from a value. And certain characters, like a leading @ or a stray colon inside an unquoted value, can confuse the parser unless the value is wrapped in quotes. When the validator flags a line, it is usually one of these.

As with any validator, this confirms the YAML is well formed, not that it holds the settings your particular tool expects, which is a separate check.

Questions people ask

What does valid mean here?

It means the YAML parses correctly as structured data: the indentation, keys, and values all follow YAML's rules. It does not check that the contents are what your application needs.

Why is it complaining about tabs?

YAML does not allow tabs for indentation, only spaces. If your file was indented with tabs, convert them to spaces and it should pass.

Can it check a Docker Compose or CI file?

Yes. It validates any YAML, including config files like those, for correct syntax. It does not verify the settings are right for that specific tool, only that the YAML itself is sound.

Is my YAML uploaded?

No. The check runs in your browser, so nothing you paste or upload leaves your machine.

References

  1. Nodeca. js-yaml: JavaScript YAML parser and dumper. https://github.com/nodeca/js-yaml
  2. YAML. YAML Ain't Markup Language (YAML) version 1.2. https://yaml.org/spec/1.2.2/

Sugam Baskota

Sugam Baskota is a senior software engineer and Computer Science graduate from UT Arlington, with interests in user scripts, browser extensions, developer tooling, and productivity systems. He spends time building practical utilities and extensions in the kinds of workflows Eon is designed to simplify. At Eon Tools, he reviews useful, password, and developer tools.

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