XML was the default data format for web services in the early 2000s, but JSON has become the overwhelming default for new APIs. The shift wasn't arbitrary — JSON solves several real pain points XML had.

Where JSON wins

• Smaller payload size, since there's no closing tag for every element
• Native compatibility with JavaScript, which runs both the browser and a huge share of backend services
• Simpler, more human-readable structure for nested data

Where XML still holds on

Some enterprise systems, older SOAP-based services, and document-centric formats like RSS still rely on XML, largely because of its strong schema validation and long-standing infrastructure investment that's expensive to replace.

Working with either format

When you're consuming a JSON API response, formatting it with proper indentation makes nested structures far easier to read than the minified, single-line blob most servers return by default — a formatter turns that dense string into a readable, navigable tree in one click.