YAML Validator & Formatter
Paste your YAML to validate, format, and convert it. Everything happens in your browser — your data stays private.
Validation results will appear here...
About YAML
YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files, data exchange, and infrastructure-as-code tools like Docker Compose, Kubernetes, Ansible, and GitHub Actions.
Unlike JSON, YAML uses indentation to denote structure, supports comments with #, and provides a more readable syntax for complex nested data. This tool validates your YAML syntax, reports errors with line numbers, and can convert to JSON for interoperability.
Features
- Validate YAML syntax with detailed error messages and line numbers
- Format and beautify YAML with consistent indentation
- Convert YAML to JSON for use with APIs and other tools
- Supports key-value pairs, nested objects, arrays, strings, numbers, booleans, null, comments, and multiline strings
- 100% client-side — your data never leaves your browser
YAML vs JSON Comparison
| Feature | YAML | JSON |
|---|---|---|
| Comments | Supported (#) |
Not supported |
| Readability | Highly readable, minimal syntax | Verbose with braces and quotes |
| Data types | Strings, numbers, booleans, null, dates, lists, maps | Strings, numbers, booleans, null, arrays, objects |
| Quoting strings | Optional (most cases) | Always required (double quotes) |
| Multiline strings | Native support (| and >) |
Must use \n escape |
| Structure | Indentation-based | Brace-based |
| Trailing commas | N/A (no commas used) | Not allowed |
| Common use cases | Config files, Docker, Kubernetes, CI/CD | APIs, web services, data storage |
| File extensions | .yaml, .yml |
.json |
YAML Syntax Quick Reference
| Syntax | Example | Description |
|---|---|---|
| Key-value pair | name: John |
Basic mapping entry |
| Nested object | server: |
Indented child keys |
| List / Array | items: |
Dash-prefixed items |
| Comment | # This is a comment |
Lines starting with # |
| Boolean | debug: true |
true, false, yes, no, on, off |
| Null | value: null |
null, ~, or empty value |
| Multiline (literal) | text: | |
Preserves newlines |
| Multiline (folded) | text: > |
Joins lines with spaces |
| Quoted string | name: "hello: world" |
Required when value contains special chars |
| Inline list | tags: [a, b, c] |
JSON-style flow sequence |
| Inline object | point: {x: 1, y: 2} |
JSON-style flow mapping |