JSON to Dart Converter
Convert JSON data to Dart class definitions with null safety, fromJson/toJson methods, and immutable properties. Generate Flutter-ready models with proper type mappings and modern Dart syntax for seamless API integration.
Conversion Options
Recommended Settings
Dart & Flutter Best Practices
- •Use final fields for immutability - essential for Flutter widgets and state management
- •Enable null safety (Dart 2.12+) to prevent null reference errors at compile time
- •Generate fromJson/toJson for JSON serialization with packages like json_serializable
- •Use camelCase for field names and PascalCase for class names (Dart convention)
- •Add copyWith methods for immutable state updates in BLoC, Provider, or Riverpod
Type Mapping & Null Safety
- •JSON strings → String, numbers → int/double, booleans → bool
- •JSON arrays → List<T> with proper element type inference
- •JSON null values → Type? (nullable) when null safety is enabled
- •Nested objects create separate class definitions with proper dependencies
- •Use required keyword in constructors for non-nullable fields
Pro Tips
- •Generated classes use PascalCase naming and fields use camelCase (Dart standard)
- •fromJson/toJson methods work seamlessly with json.decode() and json.encode()
- •copyWith enables immutable state updates without modifying original objects
- •All processing happens in your browser - your JSON never leaves your device
Most Popular
Most users enable fromJson, toJson, and final fields for production Flutter apps
When to Use This Tool
Generate Dart model classes from JSON API responses for Flutter apps. Create type-safe data models with proper null safety, immutable properties, and serialization methods. Perfect for REST APIs, Firebase, GraphQL, or any JSON-based backend.
Create immutable state classes for BLoC, Provider, Riverpod, or Redux patterns. Generated copyWith methods enable efficient state updates without mutations. Works seamlessly with popular Flutter state management solutions.
Use generated classes as foundation for json_serializable, freezed, or built_value packages. The fromJson/toJson methods provide basic serialization, which can be enhanced with code generation tools for production apps.
Build type-safe API clients for Flutter apps by converting API response schemas to Dart models. Ensure data consistency, catch type errors at compile time, and improve developer experience with auto-complete and type inference.
How It Works
Paste your JSON data into the input field on the left
Configure options: fromJson/toJson, final fields, null safety, copyWith, toString
Click 'Convert to Dart' to generate the Dart class definition
The tool maps JSON types to Dart types with proper null safety annotations
Nested objects create separate class definitions in dependency order
Arrays generate List<T> types with proper element type casting in fromJson
Copy the Dart code to clipboard or download as a .dart model file
All processing happens in your browser - your JSON data never leaves your device
100% Private
Files never leave your device. All processing happens locally in your browser.
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Powered by Pure JavaScript for optimal performance on modern browsers.
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No data collection, no tracking, no sign-up required.
Frequently Asked Questions
What is null safety in Dart?
Null safety (Dart 2.12+) prevents null reference errors at compile time by distinguishing nullable (Type?) and non-nullable (Type) types. With null safety enabled, the tool marks fields as nullable (?) if they have null values in the JSON, helping catch potential null errors before runtime.
When should I use the copyWith method?
Use copyWith for immutable state updates in Flutter state management (BLoC, Provider, Riverpod). Instead of modifying objects directly, copyWith creates a new instance with updated values while keeping original fields unchanged. Essential for functional programming patterns and Flutter rebuilds.
How do fromJson and toJson methods work?
fromJson is a factory constructor that deserializes JSON (Map<String, dynamic>) into a Dart object. toJson serializes the object back to JSON. These methods work with json.decode() and json.encode() for API communication and data persistence in Flutter apps.
Can nested JSON objects be converted?
Yes! Nested objects automatically create separate Dart classes. The tool generates all classes in proper dependency order - nested classes first, then parent classes. Each nested class gets its own fromJson/toJson methods for complete serialization support.
What's the difference between final and const in Dart?
final means the variable can only be set once and is initialized at runtime. const means the value is a compile-time constant. For model classes, use final (not const) because object instances are created at runtime from JSON data.
Should I use json_serializable package instead?
This tool provides basic serialization for quick prototyping. For production Flutter apps, consider json_serializable, freezed, or built_value packages for advanced features like code generation, union types, and better performance. Use this tool to create initial models, then enhance with packages.
How are JSON arrays handled in Dart?
JSON arrays become List<T> in Dart where T is the element type. For primitive arrays like ["a", "b"], it's List<String>. For object arrays, it's List<ClassName> with proper fromJson mapping. Empty arrays default to List<dynamic>.
Why use camelCase for field names?
camelCase is the Dart naming convention for variables and properties, while PascalCase is for classes. The tool automatically converts JSON keys (often snake_case from APIs) to camelCase for Dart fields, following the Dart Style Guide and making code consistent with Flutter ecosystem.