JSON to Dart Class Generator

Convert JSON payloads to Dart classes with named required constructor parameters and nullable fields

Root class:

Input

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Output

Output will appear here...

What is JSON to Dart Class Generator

Last reviewed: April 18, 2026

JSON (JavaScript Object Notation) is a lightweight, human-readable data format used almost everywhere on the web for APIs, config files, and log output.

JSON to Dart Class Generator emits idiomatic Dart classes with `final` fields, named constructor parameters (marked `required` for non-nullable fields), and `?` suffix for nullable types.

Perfect for Flutter apps consuming JSON APIs — paste your sample, pick a root name, and get classes that compile in a null-safe project.

Why use it

Scaffold DTOs for Flutter apps.
Port TypeScript types to Dart.
Generate fixture models for widget tests.
Teach Dart null-safety conventions.
Prototype screens with realistic data.

Features

final fields
required constructor params
Null-safe type annotations
List<T> for JSON arrays
JSON to Dart Class Generator is handled entirely in-browser

How to use JSON to Dart Class Generator

Paste JSON. Any object or array-of-objects.
Set root class. Via toolbar.
Run. Copy the Dart classes.

Example (before/after)

JSON

{ "slug": "welcome", "title": "Hello Dart", "categories": ["intro"] }

Dart

class Article {
  final String slug;
  final String title;
  final List<String> categories;

  Article({
    required this.slug,
    required this.title,
    required this.categories,
  });
}

Common errors

fromJson / toJson

Serialization helpers aren't generated.

Fix: Add them manually or use json_serializable.

Freezed output

Not generated — this tool emits plain classes.

Fix: Copy field definitions into a Freezed class manually.

FAQ

Is null-safety respected?

Yes — nullable fields get `?` suffix; non-null are marked `required` in the constructor.

Does it generate fromJson / toJson?

No — add manually or use json_serializable.

Are nested classes generated?

Yes — each nested object becomes its own class.

Does it support Freezed?

Not directly — copy the fields into a Freezed class.

Is input uploaded?

No — Dart classes are emitted locally in your browser from the pasted JSON.

Related tools

Pair with other POJO generators and JSON tools. You can also browse the full POJO & Schema Generators category for more options.

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