YAML Tools Online – Format, Validate & Convert YAML

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Format, validate, and convert YAML and JSON locally with YAML 1.2 parsing.

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YAML developer tool guide

Format, validate, and convert YAML locally

Use the YAML workspace above to format configuration files, check YAML syntax, convert YAML to readable JSON, or turn JSON back into YAML. Parsing and conversion run in your browser, so deployment manifests, CI configuration, and application settings do not need to be uploaded to a remote service. This tool is free to use. No account or payment is required.

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What you can do here

  • YAML formatting
  • YAML syntax validation
  • YAML to JSON conversion
  • JSON to YAML conversion
  • .yaml and .yml file import
  • Browser-local processing

Steps

  1. Paste YAML or import a .yaml or .yml text file.
  2. Choose Format, Validate, YAML → JSON, or JSON → YAML from the toolbar.
  3. Review parser errors or the converted output before using the result.
  4. Copy the result or download it with a mode-specific file extension.

Work with YAML configuration without uploading it

YAML often contains infrastructure, CI, deployment, and application settings that are not appropriate to send to an unknown conversion endpoint. VetaTool loads the YAML parser only when this tool is used and performs parsing and serialization locally in the browser.

The workspace accepts pasted text and local .yaml or .yml files. Large inputs use the same manual processing guard as the rest of the toolbox so repeated edits do not continuously trigger expensive parsing.

Format and validate YAML with a real parser

Formatting parses the YAML document and serializes it with consistent indentation while preserving document comments where the parser can retain them. Validation uses the same parser and reports syntax problems instead of treating YAML as plain text.

Duplicate mapping keys and malformed indentation are parser errors rather than formatting choices. Fix those errors before converting the document to JSON or using it as application configuration.

  • Normalize readable indentation for configuration review.
  • Check syntax before committing deployment or CI files.
  • Inspect parser feedback without sending configuration to a backend.

Convert YAML and JSON in either direction

YAML → JSON is useful when an API, test fixture, or debugging workflow expects JSON. The converter resolves the parsed YAML data model and emits two-space JSON for inspection or download.

JSON → YAML first requires valid JSON and then serializes the parsed value as YAML. Comments cannot be invented during this direction because JSON does not carry comment information.

YAML formatting example

A compact flow-style list becomes readable block YAML while the parsed values stay the same.

YAML input

service:
  name: api
  ports: [8080, 8081]
  enabled: true

Formatted YAML

service:
  name: api
  ports:
    - 8080
    - 8081
  enabled: true

Common questions

Frequently asked questions

Does the YAML tool upload my configuration?

No. YAML parsing, formatting, validation, and JSON conversion run locally in your browser.

Can I open .yaml and .yml files?

Yes. The import control accepts both .yaml and .yml text files up to the toolbox import limit.

Does YAML formatting preserve comments?

The formatter works from a parsed YAML document and preserves comments that the YAML parser associates with the document structure.

Can I convert YAML to JSON and JSON to YAML?

Yes. Use the two conversion modes in the same workspace or open the dedicated YAML-to-JSON and JSON-to-YAML pages.

Recommended next steps

YAML Validator Online – Check YAML SyntaxCheck YAML syntax with parser errors and browser-local processing.YAML to JSON Converter OnlineConvert parsed YAML data into readable JSON.JSON to YAML Converter OnlineConvert valid JSON objects and arrays into YAML.

Looking for broader references? Browse all developer guides.

Debugging a specific YAML issue? Browse YAML troubleshooting.