JSON Formatter & Validator

Paste JSON below to pretty print, validate, or minify it instantly — everything runs locally in your browser. Working with typed frontends? Convert the same JSON into types with the JSON to TypeScript interface generator.

Reference

JSON notes

What is JSON?

JSON (JavaScript Object Notation) is a lightweight data format for structured objects, arrays, strings, numbers, booleans, and null values. It is widely used in REST APIs, configuration files, logs, and frontend applications.

How does the JSON tool work?

The JSON formatter parses the input with the browser-native JSON parser. Valid JSON can be pretty printed with indentation for readability or minified into a compact one-line string for transport and storage. Invalid JSON returns the parser error so you can quickly find syntax problems.

When should you use JSON?

  • Formatting API responses from REST and GraphQL services
  • Validating JSON payloads before sending them to an endpoint
  • Debugging package, app, and infrastructure configuration files
  • Pretty printing compact JSON logs for easier reading
  • Minifying JSON data before copying it into tests or requests

What are the limitations of JSON?

  • JSON does not allow comments or trailing commas
  • Object property names must be wrapped in double quotes
  • Dates are represented as strings, not native date values
  • Undefined, NaN, Infinity, functions, and classes are not valid JSON values
  • Very large JSON documents may be slow to format in the browser

JSON examples

format {"name":"John","age":30} -> { "name": "John", "age": 30 }
minify { "name": "John", "age": 30 } -> {"name":"John","age":30}
validate {"status":"ok","items":[1,2,3]} -> Valid JSON
invalid {"name":"John",} -> Unexpected token } in JSON
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