YAML Validator
Catch YAML mistakes before they break a deployment. Paste a Docker Compose, Kubernetes, GitHub Actions or any other YAML file to find indentation and syntax errors with line numbers, detect duplicate keys, and see exactly how the file will be read — as JSON.
Paste YAML and it's parsed with the yaml library (YAML 1.2). Errors show the line and column with the offending line; valid files are shown converted to JSON and as normalised YAML, with multi-document files (---) counted. Duplicate keys, which many parsers silently accept, are reported as errors.
Zero Server Uploads
Files process in local RAM
Instant WASM Speed
No waiting queues or lags
Unlimited Batching
Convert files without limits
Suggest a Feature or Improvement for YAML Validator
Need custom options, higher limits, or extra format support? Let our engineering team know!
How to use YAML Validator
- 1Paste your YAML.
- 2Fix errors at the lines shown — usually indentation.
- 3Check the JSON view matches what you intended.
- 4Copy the JSON or normalised YAML.
Common YAML mistakes
Tabs for indentation (YAML only allows spaces), inconsistent indentation within a list or map, a missing space after a colon, unquoted values containing : or #, and duplicate keys. The “Norway problem” (NO read as false in YAML 1.1) is another trap — quote ambiguous strings.
Seeing the JSON version is the quickest way to confirm lists and nesting are what you meant.
Related tools
Validate JSON with the JSON Validator, check cron schedules in workflow files with the Cron Expression Generator, and check XML with the XML Validator.
Frequently Asked Questions
Does it check Kubernetes or Compose schemas?
It validates YAML syntax and structure, not whether fields are valid for a specific tool. Use kubectl --dry-run or docker compose config for schema checks.
Is my code or data uploaded?
No. Everything runs in your browser; nothing you paste is sent to a server or stored.
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