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Expensico

YAML Validator

Validate YAML and see errors with line numbers, then view the parsed result as JSON. Ideal for Kubernetes, Docker Compose and CI files.

Runs in your browser. Everything you enter stays on your device. Nothing is sent to a server.

How to use the YAML Validator

  1. Paste YAML or open a .yml/.yaml file. The example contains a deliberate tab error.
  2. Read the error with its line and column, fix it, and the check re-runs instantly.
  3. Inspect the parsed result as JSON to confirm values mean what you think.

Common YAML mistakes

  • Tabs for indentation. YAML forbids tab characters in indentation — use spaces.
  • Inconsistent indentation inside the same block.
  • Missing space after a colon: key:value is a single string, not a key/value pair.
  • Unquoted special values: yes, no, on, off and 08 may be read as booleans or octal by YAML 1.1 tools. Quote them when you mean text.
  • Colons or # in values such as URLs with ports or comments in passwords — quote the value.

Why show the result as JSON?

A YAML file can be syntactically valid but mean something different from what you intended. Seeing the parsed structure — which items are lists, which values are numbers — catches those mistakes. Convert files in either direction with YAML to JSON and JSON to YAML.

Frequently asked questions

Does it validate Kubernetes or Docker Compose schemas?

It validates YAML syntax, not a specific schema. A Kubernetes manifest with a misspelled field will still be valid YAML.

Are multiple documents (---) supported?

Yes. Multi-document files are parsed into a JSON array, one item per document.

Is what I enter stored or sent anywhere?

No. Calculations and processing happen in your browser. Nothing you type is sent to our servers. Some tools remember your last input in this browser's local storage for convenience; you can clear it at any time.