YAML Formatter & Validator

What is YAML Formatter & Validator?

YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files, CI/CD pipelines, and data exchange. This tool lets you format messy YAML into clean, indented output, validate YAML syntax, and convert between YAML and JSON formats — all running entirely in your browser with no data sent to any server.

The tool uses the js-yaml library (the same parser used by many popular tools) to parse and dump YAML with proper indentation and formatting. It handles all standard YAML features including nested objects, arrays, strings, numbers, booleans, dates, and multiline strings.

Common Use Cases

• Formatting messy or minified YAML config files for readability and editing
• Validating YAML syntax before committing configuration files to version control
• Converting YAML configuration to JSON for use in JavaScript applications or APIs
• Converting JSON data to YAML for cleaner, more readable configuration files
• Checking YAML indentation and structure errors before deployment

Pro Tips

• Use the Format mode to instantly beautify minified or poorly indented YAML
• Use Validate mode to quickly check if your YAML is syntactically correct before committing
• When converting JSON to YAML, ensure your JSON uses double quotes — YAML does not support single-quoted keys in some parsers
• Use file upload for large YAML files rather than pasting — it supports .yaml, .yml, and .json files
• Pin frequently used conversions to keep them accessible in history for quick reuse

About YAML and JSON

YAML is a superset of JSON — any valid JSON is also valid YAML. However, YAML adds features like comments, multiline strings, and implicit typing that make it more readable for configuration files. The conversion tools in this app use strict parsing to ensure data integrity between formats.

Need more dev tools? Try the JSON Formatter or the Base64 Encoder. Part of the FreeQ.One tools suite.