YAML to JSON Converter Free Online Tool 2026

Last updated March 22, 2026

YAML vs JSON

YAML (YAML Ain't Markup Language) and JSON (JavaScript Object Notation) represent the same data structures but with different syntax. YAML is designed for human readability — it uses indentation instead of braces, allows comments, and supports multi-line strings natively. JSON is designed for machine parsing — it's strict, unambiguous, and universally supported.

Syntax Comparison

YAML to JSON Conversion

// Using js-yaml library
import yaml from 'js-yaml';

function yamlToJson(yamlString, pretty = true) {
  try {
    const parsed = yaml.load(yamlString);
    return JSON.stringify(parsed, null, pretty ? 2 : 0);
  } catch (e) {
    throw new Error(`YAML parse error: ${e.message}`);
  }
}

// Example
const yamlInput = `
name: John Doe
age: 30
address:
  street: 123 Main St
  city: Springfield
hobbies:
  - reading
  - coding
`;

console.log(yamlToJson(yamlInput));
// {
//   "name": "John Doe",
//   "age": 30,
//   "address": { "street": "123 Main St", "city": "Springfield" },
//   "hobbies": ["reading", "coding"]
// }

YAML Gotchas

• Norway problem: NO is parsed as boolean false in YAML 1.1. Use quotes: "NO".
• Octal numbers: 010 is parsed as 8 (octal) in YAML 1.1. Use 0o10 in YAML 1.2.
• Tabs: YAML does not allow tabs for indentation — only spaces.
• Duplicate keys: YAML allows duplicate keys; the last value wins (behavior is undefined).