JSON to Dart, Kotlin & Swift Converter
Paste any JSON API response and instantly generate type-safe model classes for Dart (Flutter), Kotlin (Android), and Swift (iOS). Handles nested objects, arrays, snake_case conversion, and serialization methods.
How the JSON to Model Class Converter Works
This tool parses your JSON input using the browser's native JSON parser and analyzes the structure to determine the correct type for every field. It then generates strongly-typed model classes in your chosen language. Nested objects automatically produce separate classes, arrays are typed based on their contents, and snake_case keys are converted to idiomatic camelCase property names with the appropriate serialization annotations to maintain JSON compatibility.
Type Mapping
JSON strings map to String in all three languages. JSON integers map to int (Dart), Int (Kotlin), and Int (Swift). JSON floats map to double (Dart), Double (Kotlin), and Double (Swift). JSON booleans map to bool (Dart), Boolean (Kotlin), and Bool (Swift). Arrays become List<T> (Dart/Kotlin) or [T] (Swift). Nested objects become references to generated child classes.
Why Generate Model Classes from JSON?
Working with raw JSON dictionaries in mobile applications leads to runtime crashes, typos in key names, and missing type checks. By generating typed model classes, you catch data mismatches at compile time rather than in production. Every property has an explicit type, every nested object has its own class, and serialization logic is generated automatically so you never manually write repetitive parsing code again.
Dart and Flutter
Flutter developers commonly use plain Dart classes with fromJson factory constructors and toJson methods for JSON serialization. This converter generates those methods automatically, including correct type casting with as int, as String, and List<T>.from() patterns. The generated code works directly with dart:convert and packages like http without any additional dependencies.
Kotlin and Android
Kotlin data classes are the standard pattern for API response models on Android. The converter generates concise data class declarations with val properties. When JSON keys use snake_case, the generator adds @SerializedName annotations for Gson compatibility while keeping property names in idiomatic camelCase. The output is ready for use with Retrofit, Moshi, or Kotlinx Serialization.
Swift and iOS
Swift structs conforming to Codable are the modern approach to JSON parsing on Apple platforms. The converter generates struct definitions with let properties and automatically creates CodingKeys enums when JSON keys differ from Swift property names. The generated code works directly with JSONDecoder and JSONEncoder from Foundation without any third-party libraries.
Privacy and Security
All parsing and code generation runs entirely in your browser using JavaScript. Your JSON data, which may contain sensitive API responses, authentication tokens, or user records, is never transmitted to any external server. You can safely use this tool with production data. Verify by monitoring the network tab in your browser developer tools.