What is a JSON file?
JSON is a lightweight text format for structured data, standardised as ECMA-404. It supports objects, arrays, strings, numbers, booleans and null, and nothing else. That deliberate minimalism is why it replaced XML as the default format for web APIs and configuration.
At a glance
- Full name
- JavaScript Object Notation
- Extensions
- .json
- Type
- Data
- Introduced
- 2001 (ECMA-404 in 2013)
- Created by
- Douglas Crockford
- Compression
- None
- MIME type
- application/json
Strengths
- Native support in virtually every programming language
- Human-readable and simple to validate
- Handles nested and hierarchical data cleanly
Limitations
- No comments, which makes it awkward for configuration files
- No date type, so dates are strings by convention
- Verbose compared with binary formats
When to use JSON
API payloads, configuration and any nested data structure.
You need comments or anchors in config (use YAML), or flat tabular data (use CSV).
Convert JSON files
Every tool below runs in your browser unless it is labelled otherwise, so the file stays on your device.
JSON to TypeScript
Turns a JSON object into ready-to-use TypeScript interfaces, inferring nested object types automatically as it walks the structure.
JSON ⇄ CSV
Converts JSON arrays into CSV spreadsheets, or CSV files back into JSON, correctly handling quoted, escaped, and nested values.
JSON Formatter & Validator
Validates and pretty-prints JSON with custom indentation, pointing out the exact line and column of any parse error found.
YAML ⇄ JSON
Converts YAML configuration files into JSON, or JSON objects back into readable, properly indented YAML syntax instantly.
XML ⇄ JSON
Converts XML documents into JSON, or JSON objects back into well-formed XML markup with correct nested element structure.
JSON Diff
Compares two JSON objects side by side and highlights every key, value, and structural difference found between the two.
JSON conversions
Each page states what the target format cannot carry before you run it.
JSON compared
Related data formats
Last updated 2026-08-03