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Hazuu Tools

YAML Validator

Validate your YAML syntax instantly with precise error locations and JSON conversion.

YAML Input
JSON Output
Valid YAML will be converted to JSON here...
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About YAML Validator

YAML is the configuration language of modern infrastructure: Kubernetes manifests, Docker Compose files, GitHub Actions workflows, Helm charts, Ansible playbooks, and application settings files all depend on it. Because YAML uses whitespace indentation to express structure, a single misaligned space or an accidentally inserted tab character can silently break a deployment, cause a CI job to fail to parse, or prevent a Kubernetes pod from starting. YAML Validator catches those errors before they reach production by parsing your document with js-yaml — the same parser that powers many Node.js frameworks and Kubernetes tooling — and reporting the exact line and column of every syntax problem.

Use this tool when you need a direct answer to a single question: is this YAML valid? When your document passes, the tool converts it to formatted JSON on the right panel so you can visually confirm that YAML structures, data types, and nested objects were interpreted exactly as you intended. This is particularly valuable when debugging YAML anchors, multi-line string blocks, or mixed sequence/mapping hierarchies that are easy to misjudge by eye.

Every validation runs entirely in your browser using the js-yaml library loaded locally. Your Kubernetes secrets, API credentials, database passwords, and CI/CD tokens in YAML config files are never uploaded, logged, or transmitted to any server. The tool is completely free with no account required, no rate limits, and no file-size cap.

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Key Features

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Precise error location

When your YAML is invalid, the validator reports the exact line number and column where parsing stopped. Jump straight to the problem without scanning large manifests by eye.

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Automatic YAML-to-JSON preview

Every valid document is immediately rendered as formatted JSON in the right panel, letting you confirm nested structures, data types, and array contents are parsed as intended.

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File upload support

Load any .yaml, .yml, or .txt file directly from disk. The file is read locally by your browser — no upload, no network request, regardless of file size.

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One-click sample fixtures

Instantly load a pre-built valid or invalid YAML document to verify the tool is working, explore what specific error messages look like, or test edge cases like incorrect indentation or unclosed strings.

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100% client-side with js-yaml

Validation runs in your browser using js-yaml, a spec-compliant YAML 1.2 parser. Kubernetes secrets, database credentials, and API tokens in your config stay on your machine.

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Handles tabs vs spaces detection

YAML forbids tab characters for indentation. The validator explicitly identifies tab-related errors alongside the usual malformed mapping, bad sequence indent, and unclosed-quote errors that commonly appear in real config files.

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How to Use

01

Paste Your YAML

Copy your YAML configuration or data and paste it into the editor on the left.

02

Validate

Click "Validate" to check syntax. Errors are shown with exact line and column numbers.

03

View as JSON

Valid YAML is automatically converted to JSON on the right for easy inspection and comparison.

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Example

The validator catches an incorrect over-indentation on line 7 that would cause a Kubernetes or Ansible parser to reject the file. The JSON output confirms the correct structure once the error is fixed.

YAML input (contains an error)
app:
  name: MyApplication
  version: 2.1.0
  settings:
    theme: dark
      nested_wrong: true
  list:
    - item1
    - item2
   - bad_indent
JSON output (on valid input)
{
  "app": {
    "name": "MyApplication",
    "version": "2.1.0",
    "settings": {
      "theme": "dark"
    },
    "list": [
      "item1",
      "item2"
    ]
  }
}
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Common Use Cases

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    Pre-flight checking Kubernetes and Helm manifests

    Before running kubectl apply or helm upgrade, paste your Deployment, Service, or values.yaml here to confirm it parses without errors. Catching a misaligned indent locally is far faster than reading a cryptic apiserver rejection message.

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    Debugging CI/CD pipeline failures caused by bad YAML

    GitHub Actions, GitLab CI, and CircleCI surface YAML parse errors as cryptic workflow failures. Paste the offending .yml file to get a line-and-column error location you can fix immediately, rather than pushing experimental commits to trigger re-runs.

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    Verifying YAML structure after manual editing

    Config files edited by hand — Ansible playbooks, Docker Compose overrides, or application settings — often accumulate indentation drift over time. Validate after any manual edit to confirm the structure is still intact before committing.

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    Inspecting parsed structure via JSON output

    When you are unsure whether a YAML anchor, merge key, or multi-line block string is being interpreted as intended, the JSON preview makes the parsed data structure explicit — showing you exactly how the YAML parser sees your document.

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    Onboarding to YAML syntax rules

    Developers new to YAML often hit confusing errors around tabs versus spaces, bare colons in strings, or implicit type coercion of values like true and 1.0. Use the invalid sample fixture to explore these rules interactively and read descriptive error messages in a safe environment.

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Frequently Asked Questions

What is a YAML Validator? expand_more
A YAML Validator checks whether a document follows valid YAML syntax. It catches indentation errors, invalid mapping structures, duplicate keys, and other syntax issues, reporting the exact location of each error to help you fix problems quickly.
What common YAML errors does this catch? expand_more
The validator catches inconsistent indentation, tab characters (YAML requires spaces), malformed mappings and sequences, unclosed quotes, duplicate keys, and invalid special characters like bare colons inside unquoted values.
Is my YAML data secure? expand_more
Yes. All validation runs entirely in your browser using the js-yaml library. Your data never leaves your machine and is not sent to any external server. This includes Kubernetes secrets, CI/CD credentials, and database passwords stored in config files.
Why does it convert YAML to JSON? expand_more
Showing the JSON representation helps you verify that your YAML structure is being interpreted as intended. It makes nested objects, arrays, data types, and the effect of YAML anchors and merge keys explicit and easy to inspect — especially useful when debugging config files with complex nesting.
How is YAML Validator different from YAML Formatter? expand_more
YAML Validator answers a single yes/no question: does this document parse correctly? It shows you where errors are but does not rewrite your document. YAML Formatter assumes or repairs the document and outputs it with consistent, configurable indentation. Use the Validator first to confirm the document is syntactically correct, then use the Formatter if you need to standardise the indentation style for a codebase or style guide.
How is YAML Validator different from JSON Validator? expand_more
JSON Validator uses the browser native JSON.parse to check JSON syntax, which is a stricter, simpler format. YAML Validator handles the full YAML specification — indentation-based structure, block and flow styles, multi-line strings, anchors, aliases, and implicit type coercion — using js-yaml as the parser. Use YAML Validator for any .yaml or .yml file; use JSON Validator for .json files.
Can this tool validate multi-document YAML files? expand_more
js-yaml's load function processes the first YAML document in the input. Files containing multiple documents separated by --- delimiters may produce unexpected results. For single-document config files — the most common case for Kubernetes manifests, Docker Compose, and application settings — the validator works correctly.
Why does YAML reject tab characters? expand_more
The YAML specification explicitly forbids tab characters for indentation because different editors display tabs at different widths, making indentation ambiguous. YAML requires spaces only, and the validator reports a clear error when tabs are detected so you can replace them with the appropriate number of spaces.