JSON vs XML

The same data, two formats

Here is a user object represented in both formats:

JSON:

{
  "user": {
    "id": 1,
    "name": "Ana García",
    "email": "ana@example.com",
    "roles": ["admin", "editor"],
    "active": true
  }
}

XML:

<?xml version="1.0" encoding="UTF-8"?>
<user>
  <id>1</id>
  <name>Ana García</name>
  <email>ana@example.com</email>
  <roles>
    <role>admin</role>
    <role>editor</role>
  </roles>
  <active>true</active>
</user>

The JSON version is 109 characters. The XML version is 227 — more than twice as long for identical data.

Side-by-side comparison

When to use JSON

• REST APIs — JSON is the de facto standard for web APIs
• Configuration files — package.json, tsconfig.json, .eslintrc
• JavaScript / browser apps — no parsing overhead, natively understood
• NoSQL databases — MongoDB, Firebase, CouchDB store JSON documents
• Data with complex nesting — arrays of objects are natural in JSON

When to use XML

• Enterprise systems — SOAP web services, SAP, legacy ERP integrations
• Document formats — Office Open XML (docx, xlsx), SVG, RSS/Atom feeds
• Configuration with comments — Maven pom.xml, Android layouts, Spring
• Publishing and content — DITA, DocBook, XHTML
• When you need attributes — mixing data and metadata on the same element

XML features JSON lacks

XML has capabilities that JSON genuinely does not:

• Attributes — metadata on elements without extra nesting: <price currency="USD">9.99</price>
• Mixed content — text mixed with child elements, common in documents: <p>Hello <b>world</b></p>
• XSLT — transform XML into HTML, other XML, or any text format using stylesheets
• XPath / XQuery — powerful query language for selecting nodes in a document
• DTD and XSD — mature, well-established schema validation languages

The verdict

For most new web development work, JSON is the right choice. It is smaller, faster to parse, and natively understood by JavaScript.

Use XML when you are integrating with systems that require it, working with document formats (SVG, Office), or need XML-specific features like XSLT or XPath.

The choice is rarely both/and — the format is usually dictated by the system or protocol you are integrating with.