YAML Formatter/Validator

The YAML Formatter & Validator is a free online tool for developers and DevOps engineers to format, validate, minify, and convert YAML configuration files. Whether you're working with Kubernetes manifests, Docker Compose files, GitHub Actions workflows, Ansible playbooks, or any YAML-based configuration, this tool helps you ensure correct syntax and clean formatting instantly.

What is YAML?

YAML (YAML Ain't Markup Language) is a human-readable data serialization language designed for configuration files and data exchange. Unlike JSON, YAML relies on indentation (spaces, not tabs) to define structure, making it visually clean but sensitive to formatting errors. YAML supports features like comments (#), multi-line strings (| and >), anchors (&) and aliases (*) for reusing values, and multi-document files separated by ---.

Features

YAML vs JSON Comparison

Common YAML Errors and How to Fix Them

Indentation errors

YAML requires consistent indentation with spaces (never tabs). Mixing indentation levels or using tabs will cause a parse error. Use this formatter to automatically fix indentation to a consistent 2 or 4-space style.

Colon in values without quoting

A value like url: http://example.com may fail because the colon in http: is interpreted as a key separator. Wrap such values in quotes: url: "http://example.com".

Special characters in strings

Values starting with {, [, *, &, !, %, @, or ` must be quoted. Boolean-like values (yes, no, true, false) are auto-converted — quote them if you mean literal strings.

How to Use This Tool

1. Paste your YAML: Copy and paste your YAML configuration into the input text area. You can also click a quick example button (Kubernetes, Docker Compose, GitHub Actions, or Anchors & Aliases) to load sample YAML.
2. Select an action: Choose Format & Beautify for readable output, Minify for compact single-line output, Validate Only to check syntax, or Convert to JSON to transform your YAML into JSON format.
3. Configure options: Optionally adjust the indent size (2 or 4 spaces) and enable Sort Keys to alphabetically order mapping keys.
4. Click Format YAML: Click the button to process your data. Results appear instantly below with syntax highlighting.
5. Review and copy results: Review the highlighted output, check YAML statistics (nesting depth, element counts, file size), and copy or download the result.

Frequently Asked Questions

What is YAML?

YAML (YAML Ain't Markup Language) is a human-readable data serialization language commonly used for configuration files. It is widely used in Kubernetes manifests, Docker Compose files, GitHub Actions workflows, Ansible playbooks, and many other DevOps and application configuration scenarios. Unlike JSON, YAML uses indentation to represent structure instead of braces and brackets.

How do I validate YAML syntax online?

Paste your YAML into the input area and select "Validate Only" from the action dropdown, then click Format YAML. The tool will check your YAML syntax and report any errors with the exact line number, column, and a description of the problem so you can fix it quickly.

Can I convert YAML to JSON?

Yes. Select "Convert to JSON" from the action dropdown and click Format YAML. The tool will parse your YAML and output equivalent JSON with proper formatting. This is useful when you need to use YAML data in a JSON-only context or compare structures between the two formats.

What is the difference between YAML and JSON?

YAML uses indentation for structure and supports comments, anchors, aliases, and multi-line strings natively. JSON uses braces, brackets, and quotes, and does not support comments. YAML is generally more human-readable and preferred for configuration files, while JSON is more widely used for data exchange between APIs and applications.

Is my YAML data secure when using this tool?

Yes. All YAML processing happens on the server during your request using safe parsing (yaml.safe_load) which prevents code execution. Your data is not stored, logged, or shared with any third party. The connection is encrypted via HTTPS.