JSON Validator & Formatter

What is JSON?

JSON (JavaScript Object Notation) is a lightweight data interchange format. Despite its name, JSON is language-independent and used across virtually all modern programming languages. Its simplicity and human readability have made it the dominant format for web APIs, configuration files, and data storage.

JSON syntax uses:

• Objects - Key-value pairs enclosed in curly braces {}
• Arrays - Ordered lists enclosed in square brackets []
• Values - Strings, numbers, booleans, null, objects, or arrays

{
  "name": "John Doe",
  "age": 30,
  "active": true,
  "roles": ["admin", "user"]
}

Common JSON syntax errors

Missing or extra commas:

// Wrong - trailing comma
{"name": "John", "age": 30,}

// Correct
{"name": "John", "age": 30}

Single quotes instead of double:

// Wrong
{'name': 'John'}

// Correct
{"name": "John"}

Unquoted keys:

// Wrong
{name: "John"}

// Correct
{"name": "John"}

Trailing decimal points:

// Wrong
{"price": 10.}

// Correct
{"price": 10.0}

Comments (not allowed in JSON):

// Wrong - comments aren't valid JSON
{
  "name": "John" // This breaks parsing
}

JSON vs JavaScript objects

While JSON syntax is based on JavaScript object literals, they’re not identical:

Why format JSON?

Readability - Minified JSON is nearly impossible to read. Proper indentation reveals structure at a glance.

Debugging - Formatted JSON makes it easier to spot missing brackets, misplaced commas, and structural issues.

Comparison - Consistently formatted JSON can be compared with diff tools to identify changes.

Documentation - Formatted JSON in API documentation is easier for developers to understand.

JSON best practices

Use meaningful key names - "firstName" is clearer than "fn" or "f".

Be consistent - Choose camelCase or snake_case and stick with it throughout your API.

Avoid deep nesting - Deeply nested JSON is hard to work with. Consider flattening structures where sensible.

Keep payloads reasonable - Large JSON responses are slow to parse. Paginate collections and allow field selection.

Validate on input - Always validate JSON from external sources before processing.

JSON in APIs

JSON is the standard format for REST APIs. A typical API response:

{
  "status": "success",
  "data": {
    "user": {
      "id": 123,
      "email": "user@example.com"
    }
  },
  "meta": {
    "timestamp": "2024-01-15T10:30:00Z"
  }
}

HTTP headers should indicate JSON content:

Content-Type: application/json

How this tool works

Paste your JSON to validate its syntax and format it with proper indentation. The validator identifies exactly where syntax errors occur, making them easy to fix. Powered by a QuantCDN Edge Function.