YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files. It uses indentation to represent structure, making it more readable than JSON or XML. YAML is used by Docker Compose, Kubernetes, Ansible, GitHub Actions, and many other tools.

What are common YAML syntax errors?

The most common YAML errors are: incorrect indentation (YAML requires consistent spaces, never tabs), missing colons after keys, unquoted strings containing special characters (like : or #), and mixing spaces and tabs. This validator shows the exact line where the error occurs.

What is the difference between YAML and JSON?

YAML and JSON can represent the same data structures but differ in syntax. YAML uses indentation and is more human-readable, while JSON uses braces and brackets. YAML supports comments, anchors, and multi-line strings that JSON does not. Every valid JSON document is also valid YAML, but not vice versa.

YAML Validator — Check & Convert Online

YAML Validator Online

Validate YAML syntax and convert between YAML and JSON.

Processed locally in your browser

YAML Input

Upload

JSON Output

This tool implements a common YAML subset and may not cover all edge cases of the YAML 1.2 specification (e.g., anchors, aliases, merge keys, complex tags). For production use, consider a full-spec library. All processing happens locally in your browser — no data is sent to any server.

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How to Use

Validate YAML syntax and convert to JSON with this free online tool.

Paste YAML into the input area, or upload a .yaml file.
Validation runs instantly — a green banner means valid, red shows the error with line number.
Valid YAML is automatically converted to JSON in the output panel.
Toggle direction to convert JSON back to YAML.
Click Copy or Download to save the output.

All validation and conversion happens in your browser — your data never leaves your device.

Features

✓Real-time YAML validation
✓YAML to JSON conversion
✓JSON to YAML conversion
✓Error line number display
✓File upload support
✓One-click copy & download

Frequently Asked Questions

What is YAML?: YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files. It uses indentation to represent structure, making it more readable than JSON or XML. YAML is used by Docker Compose, Kubernetes, Ansible, GitHub Actions, and many other tools.
What are common YAML syntax errors?: The most common YAML errors are: incorrect indentation (YAML requires consistent spaces, never tabs), missing colons after keys, unquoted strings containing special characters (like : or #), and mixing spaces and tabs. This validator shows the exact line where the error occurs.
What is the difference between YAML and JSON?: YAML and JSON can represent the same data structures but differ in syntax. YAML uses indentation and is more human-readable, while JSON uses braces and brackets. YAML supports comments, anchors, and multi-line strings that JSON does not. Every valid JSON document is also valid YAML, but not vice versa.

YAML Validator Online

How to Use

Features

Frequently Asked Questions

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