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YAML Formatter & Validator

Clean up the indentation of a YAML file and find exactly where it breaks. Comments, anchors and every document of a multi-document file are kept.

Runs in your browser · No uploads

  • Nothing leaves your device
  • No server-imposed size limits
  • No sign-up, no watermark
  • Free

How to format YAML

  1. Paste your YAML, open a .yaml file, or try the example.
  2. Choose the indentation, and whether keys should be sorted.
  3. Copy or download the result. A mistake is shown with its line and column.

What is checked

  • Indentation that doesn't line up, and tabs used for indentation (YAML allows only spaces).
  • Unclosed brackets and quotes, and a missing space after a colon.
  • The same key twice in one mapping.
  • Every document of a file separated by ---.

Comments are kept

Many YAML tools drop comments when they reformat a file. This one keeps them, along with anchors (&name) and aliases (*name), so it is safe for GitHub Actions workflows, Docker Compose and Kubernetes files. Values are never changed: the reformatted file is the same data in a tidier layout.

Frequently asked questions

Why is my YAML invalid?

The most common causes are a tab used for indentation, a key indented one space too many or too few, and a colon inside an unquoted value. The message shows the line and column where the problem starts.

Can I convert YAML to JSON here?

Use the YAML to JSON Converter, which turns YAML into JSON and back.

Is my file uploaded?

No. Everything happens in your browser, and the page is blocked from uploading anything.