JSON Validator & Formatter 2025

Professional JSON validation and formatting tool for developers, API designers, and data analysts. Validate JSON syntax, beautify with proper indentation, minify for production, fix common errors, and validate against JSON schemas. Essential for API development, configuration management, and data processing.

Paste or type JSON data. Syntax errors are highlighted as you type.
Choose formatting style
Choose output format
Optional: Validate against JSON Schema

Professional JSON Development Tools

JSON is the backbone of modern APIs and data exchange. Our validator ensures your JSON is valid, well-formatted, and follows best practices for maintainability and performance.

Syntax Validation

Real-time syntax checking with precise error location, helpful error messages, and suggestions for common mistakes.

Smart Formatting

Beautify JSON with customizable indentation or minify for production. Maintains data integrity while optimizing format.

Schema Validation

Validate JSON against schemas to ensure API contracts are met. Support for draft-07 JSON Schema with detailed error reporting.

Error Fixing

Automatically fix common JSON errors like trailing commas, single quotes, and missing quotes around keys.

Path Explorer

Navigate complex JSON structures with path notation. Extract specific values and understand nested data relationships.

Multiple Formats

Convert between JSON, JavaScript objects, CSV, and other formats. Perfect for data migration and integration tasks.

JSON Best Practices & Common Errors

Master JSON syntax and avoid common pitfalls

❌ Common Errors

  • • Single quotes instead of double quotes
  • • Trailing commas in arrays/objects
  • • Comments (// or /* */) not allowed
  • • Unquoted keys
  • • JavaScript expressions
  • • Undefined, NaN, or Infinity values

✓ Valid JSON Types

  • • String: "Hello World"
  • • Number: 123, 45.67, -89
  • • Boolean: true, false
  • • Null: null
  • • Array: [1, 2, 3]
  • • Object: {"key": "value"}

💡 Best Practices

  • • Use consistent indentation
  • • Keep nesting levels reasonable
  • • Use meaningful key names
  • • Validate against schemas
  • • Escape special characters
  • • Use ISO 8601 for dates

🔧 String Escaping

  • • Quotes: \"
  • • Backslash: \\
  • • Newline: \n
  • • Tab: \t
  • • Unicode: \u0041
  • • Carriage return: \r

JSON Examples & Patterns

Common JSON structures and use cases

API Response

{
  "status": "success",
  "data": {
    "users": [
      {
        "id": 1,
        "name": "John Doe",
        "email": "[email protected]"
      }
    ],
    "total": 1,
    "page": 1
  },
  "timestamp": "2025-01-15T10:30:00Z"
}

Configuration File

{
  "app": {
    "name": "MyApp",
    "version": "2.0.0",
    "debug": false
  },
  "database": {
    "host": "localhost",
    "port": 5432,
    "credentials": {
      "username": "admin",
      "password": null
    }
  }
}

Nested Arrays

{
  "categories": [
    {
      "name": "Electronics",
      "products": [
        {
          "id": "P001",
          "name": "Laptop",
          "specs": {
            "cpu": "Intel i7",
            "ram": "16GB"
          }
        }
      ]
    }
  ]
}

Error Response

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid input data",
    "details": [
      {
        "field": "email",
        "message": "Invalid email format"
      }
    ]
  }
}

JSON Schema Validation

Ensure data integrity with schema validation

Example: User Profile Schema

Schema Definition

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "username": {
      "type": "string",
      "minLength": 3,
      "maxLength": 20
    },
    "email": {
      "type": "string",
      "format": "email"
    },
    "age": {
      "type": "integer",
      "minimum": 18,
      "maximum": 120
    },
    "roles": {
      "type": "array",
      "items": {
        "type": "string",
        "enum": ["admin", "user", "guest"]
      }
    }
  },
  "required": ["username", "email"]
}

Valid JSON Example

{
  "username": "johndoe",
  "email": "[email protected]",
  "age": 25,
  "roles": ["user", "admin"]
}

Invalid JSON Example

{
  "username": "jo",  // Too short
  "email": "invalid-email",  // Wrong format
  "age": 150,  // Exceeds maximum
  "roles": ["superuser"]  // Not in enum
}

Frequently Asked Questions

Expert answers to common JSON questions

What makes JSON invalid and how do I fix it? ▼

Common JSON errors include: 1) Using single quotes instead of double quotes - JSON requires double quotes for strings and keys, 2) Trailing commas - remove commas after the last element in arrays/objects, 3) Comments - JSON doesn't support // or /* */ comments, 4) Unquoted keys - all object keys must be strings in double quotes, 5) JavaScript expressions - functions, undefined, NaN are not valid JSON, 6) Incorrect escape sequences in strings. Our validator pinpoints exact error locations and can auto-fix many common issues.

What's the difference between JSON and JavaScript objects? ▼

JSON is a strict subset of JavaScript object notation. Key differences: JSON requires double quotes around all strings and keys (JS allows single quotes and unquoted keys), JSON doesn't allow trailing commas (JS does), JSON has no undefined type (JS does), JSON can't contain functions or methods (JS objects can), JSON doesn't support comments (JS does), dates must be strings in JSON (JS has Date objects). This strictness makes JSON universally parseable across all programming languages.

How does JSON schema validation work? ▼

JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It defines: data types (string, number, boolean, array, object, null), constraints (minimum/maximum values, string patterns, array lengths), required fields, default values, and complex validation rules. Schema validation ensures your JSON data conforms to expected structure, making APIs more reliable and catching errors early. It's especially useful for API contracts, configuration validation, and data quality assurance.

Should I minify JSON for production? ▼

Minifying JSON removes unnecessary whitespace, reducing file size by 20-30% typically. This is beneficial for: API responses (faster transmission), configuration files in production (smaller deployment size), client-side storage (localStorage limits), and mobile applications (bandwidth savings). However, keep formatted versions for: development and debugging, configuration files that humans edit, documentation examples, and logging/troubleshooting. Many systems use formatted JSON in development and minified in production.

How do I handle large JSON files efficiently? ▼

For large JSON files: 1) Use streaming parsers that process data incrementally rather than loading everything into memory, 2) Consider JSON Lines format (one JSON object per line) for better streaming, 3) Implement pagination in APIs instead of returning massive arrays, 4) Use compression (gzip) for transmission, 5) Split large objects into smaller, related files, 6) For validation, process in chunks rather than validating the entire file at once. Our tool handles files up to 10MB effectively in the browser.

What are JSON path expressions? ▼

JSON path expressions allow you to navigate and extract data from JSON structures. Similar to XPath for XML, JSONPath uses dot notation ($.store.book[0].title) or bracket notation ($['store']['book'][0]['title']) to access nested values. Common operators include: $ (root), . (child), [] (array index or key), * (wildcard), .. (recursive descent), and filters like [?(@.price < 10)]. This is invaluable for extracting specific data from complex JSON documents without parsing the entire structure.