XML vs JSON: Full Comparison for Developers in 2026

JSON has dominated API development since the 2010s, but XML is far from gone. This comparison helps you understand which to use and how to work with both.

Syntax comparison

The same data in both formats:

<!-- XML -->
<user id="123">
  <name>Alice</name>
  <age>28</age>
  <tags>
    <tag>developer</tag>
    <tag>python</tag>
  </tags>
</user>

// JSON
{
  "id": "123",
  "name": "Alice",
  "age": 28,
  "tags": ["developer", "python"]
}

JSON is 40% smaller and lacks the verbosity of opening/closing tags.

Key differences

• Attributes: XML supports <user id="123">. JSON has no attribute concept — id is just another key.
• Comments: XML supports <!-- comment -->. JSON does not support comments at all.
• Data types: JSON has native types (number, boolean, null, array). XML everything is text — types are defined via schema.
• Namespaces: XML has namespace support for merging documents. JSON has no equivalent.
• Mixed content: XML can mix text and elements. JSON cannot.

Performance

JSON consistently parses faster than XML. Benchmarks typically show JSON parsing at 3–10× the speed of equivalent XML. For high-throughput APIs, this is significant.

When JSON wins

• REST APIs — JSON is the universal standard
• JavaScript frontends — native parsing
• NoSQL databases — MongoDB, DynamoDB
• Microservices — lightweight, fast
• Configuration (alongside YAML)

When XML still wins

• SOAP web services — enterprise legacy systems
• Office documents — .docx, .xlsx are XML internally
• SVG graphics — Scalable Vector Graphics
• RSS/Atom feeds
• Android layouts
• Financial reporting (XBRL)
• Document-centric data with mixed content

Convert between XML and JSON