Almost every API, export button, or data pipeline eventually asks you to pick a format, and JSON, XML, and CSV are the three you'll run into constantly. They're not interchangeable — each one makes different trade-offs around structure, size, and what tools can read it.
JSON: the default for APIs and nested data
JSON (JavaScript Object Notation) represents data as nested objects and arrays — keys, values, and the ability to nest structures inside each other arbitrarily deep. This makes it the natural fit for anything with a real structure: a user object with an address that has its own fields, a list of orders each containing line items. Virtually every modern web API returns JSON by default, and every mainstream programming language parses it natively without extra libraries.
XML: verbose, but with real validation tooling
XML (Extensible Markup Language) also represents nested data, using opening and closing tags instead of JSON's braces and brackets — which makes it noticeably more verbose for the same data. Its advantage is a mature ecosystem of validation tools: XML Schema (XSD) lets you define a strict contract for what a valid document must look like, which is why XML is still standard in industries with strict document requirements — finance, healthcare records, and many enterprise systems that predate JSON's dominance.
CSV: flat, and only flat
CSV (Comma-Separated Values) is rows and columns, full stop — no nesting, no structure beyond a flat table. That simplicity is exactly why it opens directly in Excel or Google Sheets with zero setup, and why it's the standard format for any tabular export: a list of transactions, a contact list, a spreadsheet of inventory. The moment your data has a nested relationship — an order with multiple line items, for instance — CSV forces you to either flatten it awkwardly or split it across multiple files.
A practical way to decide
- Talking to a modern API, or your data has nested structure? Use JSON.
- Working with a legacy enterprise system, or need strict schema validation? Use XML.
- The data is genuinely tabular — rows and columns, nothing nested? Use CSV, since it's the easiest format for a non-technical person to open and use directly.
Convert between them
Plexto has direct converters for every combination — JSON to CSV, CSV to JSON, and JSON to XML — so you're not stuck reformatting data by hand when a tool or API expects a different shape than what you have.