What is JSON vs XML in API testing and what are the differences?

Answer

JSON vs XML in API Testing

JSON (JavaScript Object Notation)

JSON is a lightweight, human-readable data format using key-value pairs.

JSON

{
  "user": {
    "id": 1,
    "name": "John Doe",
    "email": "john@example.com",
    "roles": ["admin", "editor"],
    "active": true
  }
}

XML (eXtensible Markup Language)

XML is a self-describing markup language using tags.

XML

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

Comparison

Feature	JSON	XML
Readability	Easier to read	More verbose
Size	Smaller payload	Larger payload
Parsing speed	Faster	Slower
Browser support	Native	Needs XML parser
Data types	String, number, boolean, array, object	Strings only (need schema for types)
Comments	Not supported	Supported
Attributes	No attributes	Supports attributes
Used in	REST APIs	SOAP, some legacy REST
Schema validation	JSON Schema	XSD (XML Schema Definition)

Parsing XML in Rest Assured

Java

// XML response — use XmlPath
given()
    .header("Accept", "application/xml")
    .when()
    .get("/api/users/1")
    .then()
    .statusCode(200)
    .body("user.name", equalTo("John Doe"))
    .body("user.email", equalTo("john@example.com"));

// Extract using XmlPath
XmlPath xmlPath = given()
                      .when()
                      .get("/api/users/1")
                      .then()
                      .extract()
                      .xmlPath();

String name = xmlPath.getString("user.name");

Parsing JSON in Rest Assured

Java

// JSON response — use JsonPath
given()
    .when()
    .get("/api/users/1")
    .then()
    .statusCode(200)
    .body("user.name", equalTo("John Doe"))
    .body("user.roles[0]", equalTo("admin"));

In Interviews

"Most modern REST APIs use JSON because it's lightweight, fast to parse, and natively supported by JavaScript. XML is still used in enterprise SOAP services and some legacy systems. When testing, Rest Assured supports both — JsonPath for JSON and XmlPath for XML."