Convert JSON to Code Classes Online — 10 Languages Supported

Polymorpher's JSON to Code Classes converter instantly transforms any JSON payload into strongly-typed classes for C#, Java, Python, TypeScript, Go, Kotlin, Dart, Ruby, Swift, and Rust. Whether you need to cast JSON into C# records, convert JSON to Python dataclasses, generate TypeScript interfaces, or transform JSON into Go structs — this tool handles it all in one click.

Simply paste your JSON, select a target language, and get production-ready code with proper naming conventions, type inference, and nested class support. The reverse transform feature lets you convert code classes back into JSON schema, making it a true bi-directional JSON converter.

No data is stored — your JSON stays in your browser. This is the fastest free online JSON to class generator available, powered by .NET 10 for sub-millisecond conversions.

How to use

1. Paste your JSON data into the input field
2. Select the target language (C#, Java, Python, etc.)
3. Get instantly generated code classes
4. Copy the output and use it in your project

Live Examples

{ "id": 42, "name": "Polymorpher", "active": true }

public sealed record Root(long Id, string Name, bool Active);

{ "user": { "email": "[email protected]", "roles": ["admin","editor"] } }

export interface User {
    email: string;
    roles: string[];
}
export interface Root {
    user: User;
}

{ "items": [{ "sku": "A1", "price": 9.99 }] }

@dataclass
class ItemsItem:
    sku: str
    price: float

@dataclass
class Root:
    items: List[ItemsItem]

Edge Cases Handled

• null values map to nullable types (object? in C#, Optional[object] in Python, Any? in Kotlin)
• Empty arrays produce generic list types (List<object>)
• Mixed-type numbers: integers become long/int/Int, decimals become double/float/Double
• Deeply nested objects generate separate named classes at each depth level
• Property names with underscores/hyphens are normalized to each language's naming convention (PascalCase, camelCase, snake_case)

When to Use This Tool

• Bootstrapping DTOs from a REST API response
• Generating models for JSON deserialization in any language
• Converting JSON configs to typed settings classes
• Quickly scaffolding domain models from sample data

When Not to Use

• The JSON contains deeply inconsistent structures (e.g., same field is sometimes an object, sometimes a string) — manual modeling is safer
• You need validation attributes or ORM annotations — use SQL to Classes for EF Core entities

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