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Utilerio

JSON to Model Class

Generate C#, Java or Python model classes from a JSON sample.

Generated model

The result will appear here.

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About this tool

A backend that consumes an API response, or writes one, needs a typed class to deserialize into — a C# class for a .NET service, a Java POJO for a Spring app, a Python dataclass for a script. Writing that class by hand from a JSON sample is mechanical and easy to get subtly wrong (an int that should have been a double, a missed nested object).

How to use it

  1. Pick the target language: C#, Java or Python.
  2. Paste a JSON object or array — a real API response works best.
  3. Name the root class, then copy the generated model. Nested objects get their own class, named after the property they came from.

Examples

A simple user object

{ "id": 1, "name": "Ada", "active": true }
public class Root {
    public int Id { get; set; }
    public string Name { get; set; }
    public bool Active { get; set; }
}

Common problems

A field is typed as the wrong number type — I expected a decimal but got an int.
The type is inferred from the one sample value you provided: 10 looks like an integer, 10.0 looks like a float. If a field can hold either in practice, widen the type by hand after generating.
The Java output has no Lombok annotations or builder methods.
The generated classes are plain POJOs with explicit getters and setters — a deliberate, dependency-free starting point you can adapt to your project's conventions (Lombok, records, etc.) afterward.

Frequently asked questions