JSON Formatting: How to Read, Fix, and Validate JSON

What Is JSON?

JSON (JavaScript Object Notation) is the universal format for data exchange on the web. APIs return it, config files use it, databases export it. If you work with any web technology, you work with JSON.

Its appeal is simplicity: data is represented as key-value pairs, arrays, and nested objects using a syntax that's both human-readable and machine-parseable.

JSON Structure at a Glance

{
  "name": "ToolForge",
  "version": 2,
  "tools": ["password-generator", "ip-lookup", "json-formatter"],
  "active": true,
  "meta": {
    "created": "2024-01-01",
    "count": 42
  }
}

Six valid JSON data types:

String — "hello" (double quotes only, never single)

Number — 42 or 3.14

Boolean — true or false (lowercase)

Null — null

Array — [1, 2, 3]

Object — {"key": "value"}

The Most Common JSON Errors

1. Trailing comma

{"name": "ToolForge", "active": true,}   // ❌ trailing comma
{"name": "ToolForge", "active": true}    // ✅

2. Single quotes instead of double

{'name': 'ToolForge'}   // ❌ single quotes
{"name": "ToolForge"}   // ✅

3. Unquoted keys

{name: "ToolForge"}     // ❌ key must be quoted
{"name": "ToolForge"}   // ✅

4. Comments JSON does not support comments. // comment and /* comment */ will break parsing. 5. Undefined or function values undefined and functions are not valid JSON values. They'll be stripped or cause errors.

Reading Minified JSON

APIs often return minified JSON — all whitespace stripped to save bandwidth:

{"user":{"id":1234,"name":"Alice","roles":["admin","editor"],"active":true}}

This is valid JSON but nearly impossible to read at a glance. Formatting it with proper indentation makes the structure immediately clear.

How to Format JSON Instantly

ToolForge's JSON Formatter takes any valid JSON — minified, pasted from an API response, or extracted from a log — and formats it with 2-space indentation, syntax highlighting, and instant validation.

If your JSON has an error, the formatter points to the exact line and character where parsing failed, making debugging fast.

Paste in your JSON, hit Format, and you'll have a clean, readable structure in under a second. You can also minify it back down for use in production.