XML vs JSON: Choosing a Data Interchange Format

XML used to be the default choice for data exchange; today, JSON dominates most new APIs. Understanding why that shift happened — and where XML still holds its ground — clarifies when each is actually the better tool.

Structural differences

XML wraps data in opening and closing tags (<name>VN Tools</name>), while JSON uses a more compact key-value syntax ({"name": "VN Tools"}) borrowed from JavaScript object literals. The tag-based approach makes XML inherently more verbose for the same data.

Why JSON became the default for APIs

Factor	XML	JSON
Verbosity	Higher — repeated closing tags	Lower — more compact
Native JavaScript support	Requires parsing	Native — JSON maps directly to JS objects
Schema validation	Mature (XSD, DTD)	Available but less standardized (JSON Schema)
Attributes vs elements	Supports both, adds complexity	Only key-value pairs, simpler model
Comments	Supported	Not supported in standard JSON

JSON's rise closely tracked JavaScript's rise as a dominant language for both frontend and backend development — a format that required no parsing step in JavaScript had an obvious advantage over one that did.

Where XML still holds ground

XML remains common in enterprise systems, document formats (like Office Open XML, the format behind .docx files), and contexts requiring rigorous schema validation — its maturity in that area is still ahead of JSON's ecosystem. SOAP-based web services, still used in some legacy enterprise integrations, are also XML-based by design.

A practical rule

For new web APIs and JavaScript-heavy applications, JSON is almost always the better default. For legacy enterprise integration, document formats, or contexts needing strict schema enforcement, XML may still be the required or more appropriate choice.

Frequently asked questions