YAML Formatter & Validator
Validate and format YAML and convert between YAML and JSON with exact error locations. Great for Docker and Kubernetes files. Free.
Output
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How to use YAML Formatter & Validator
- Paste YAML (or JSON) or open a file.
- Choose Validate & format, YAML → JSON, or JSON → YAML.
- Copy or download the result; errors show their line number.
Privacy
Runs entirely in your browser. Nothing you enter or open here is uploaded.
Questions
Why is 12:30 kept as text?
This tool follows YAML 1.2, where 12:30 is a string. Older YAML 1.1 parsers turned it into a number (750).
Are comments kept?
No. Formatting rebuilds the YAML from its data, so comments are dropped — keep a copy of the original.
What isn't supported?
Complex keys written with “? ” and custom tags. Anchors, aliases, merge keys (<<), multi-document files and block text are supported.