JSON vs YAML vs XML: When to Use What?

When creating config files or deciding on an API response format, have you ever wondered "which one should I use?" JSON, YAML, XML—all three express data, but when is each one the best choice?

Side-by-Side Comparison

Let's represent the same data in all three formats.

JSON

{
  "name": "John Doe",
  "age": 30,
  "skills": ["JavaScript", "Python"],
  "address": {
    "city": "New York",
    "zip": "10001"
  }
}

YAML

name: John Doe
age: 30
skills:
  - JavaScript
  - Python
address:
  city: New York
  zip: "10001"

XML

<person>
  <name>John Doe</name>
  <age>30</age>
  <skills>
    <skill>JavaScript</skill>
    <skill>Python</skill>
  </skills>
  <address>
    <city>New York</city>
    <zip>10001</zip>
  </address>
</person>

You can already see the difference. YAML is the most concise, XML the most verbose.

JSON: The Web Standard

Pros:

• Native to JavaScript (it's literally JavaScript Object Notation)
• Supported by virtually every programming language
• Fast parsing
• De facto standard for web APIs

Cons:

• No comments (inconvenient for config files)
• Strict syntax (quotes, commas required)
• Tedious for humans to edit manually

When to use: API responses, web data exchange, programmatic data storage

YAML: Human-Friendly

Pros:

• Best readability (structure via indentation)
• Supports comments (with #)
• Quotes usually optional
• Multiline string support

Cons:

• Indentation errors break things (watch for tab/space mixing)
• Parsing slower than JSON
• Advanced features (anchors, aliases) can be confusing

When to use: Config files (Docker Compose, Kubernetes, GitHub Actions), files humans edit frequently

XML: Still Alive

Pros:

• Schema validation (strict type checking with XSD)
• Supports attributes
• Namespaces prevent collisions
• XSLT for transformations

Cons:

• Verbose (sometimes more tags than data...)
• Complex and slow parsing
• Rarely used in modern web

When to use: Legacy systems, SOAP APIs, when strict schemas are required, office document formats (docx is internally XML)

Summary Table