Data Interchange Formats Guide

Why Data Formats Matter

Data interchange formats are the lingua franca of software, they let different systems talk to each other. Choosing the right format affects file size, readability, parsing speed, and schema validation. Here's a practical comparison of the most common formats.

Format Comparison

Format   Human-Readable   Comments   Schema     Best For
─────────────────────────────────────────────────────────
JSON     ✓ Good           ✗ No       JSON Schema APIs, configs, data
YAML     ✓ Excellent      ✓ Yes      JSON Schema Config files, k8s
XML      ✓ Verbose        ✓ Yes      XSD/DTD    Enterprise, SOAP
TOML     ✓ Excellent      ✓ Yes      Partial    App config (Cargo, pyproject)
CSV      ✓ Simple         ✗ No       ✗ No       Tabular data, exports

JSON

JavaScript Object Notation is the web's default data format. It's simple, widely supported, and has excellent tooling:

{
  "name": "BuildUtilities",
  "version": "2.0",
  "tools": ["json-formatter", "regex-tester"],
  "config": {
    "darkMode": true,
    "maxResults": 50
  }
}

Limitations: No comments, no trailing commas, no date type, keys must be quoted strings. See the JSON Formatting Guide for more.

XML

XML is verbose but extremely powerful, it supports namespaces, attributes, mixed content, and formal schemas:

<?xml version="1.0" encoding="UTF-8"?>
<project name="BuildUtilities">
  <version>2.0</version>
  <tools>
    <tool id="json-formatter">JSON Formatter</tool>
    <tool id="regex-tester">Regex Tester</tool>
  </tools>
</project>

Convert XML data to JSON with the XML to JSON Converter.

TOML

TOML (Tom's Obvious Minimal Language) is designed for config files. It's more readable than JSON and less error-prone than YAML:

[project]
name = "BuildUtilities"
version = "2.0"

[config]
dark_mode = true
max_results = 50

[[tools]]
id = "json-formatter"

[[tools]]
id = "regex-tester"

TOML supports native date/time types and has unambiguous semantics. Convert with the TOML to JSON Converter.

JSON Schema

JSON Schema lets you validate the structure of JSON data, required fields, types, ranges, patterns, and more:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "required": ["name", "version"],
  "properties": {
    "name": { "type": "string", "minLength": 1 },
    "version": { "type": "string", "pattern": "^\\d+\\.\\d+$" },
    "tools": {
      "type": "array",
      "items": { "type": "string" }
    }
  }
}

Generate schemas automatically with the JSON Schema Generator.

Converting Between Formats

Most data formats can be losslessly converted to JSON (the common denominator). Some conversions lose metadata. XML attributes become awkward in JSON, YAML anchors don't have a JSON equivalent.

Choosing the Right Format

APIs & web data: JSON (universal client support)
Config files: TOML or YAML (human-friendly, supports comments)
Enterprise / legacy systems: XML (schema validation, namespaces)
Tabular data: CSV (spreadsheet-friendly, compact)
Complex nested data: JSON or YAML (recursive nesting)