Does it handle nested objects and lists?

Yes — nested objects become their own classes and arrays are typed as List using the first element as the sample.

Should I enable json_serializable?

Use it if your project already runs build_runner. It adds the @JsonSerializable() annotation and the json_annotation import; otherwise the hand-written fromJson/toJson works with no codegen.

Why are fields nullable by default?

Real API responses often omit fields, so nullable fields avoid runtime crashes. Turn the switch off for required non-nullable fields.

Is my data uploaded to a server?

No. This tool runs entirely in your browser using standard web APIs, so your input never leaves your device and nothing is logged or stored on our servers.

Does it work offline and on mobile?

Yes. Once the page has loaded it keeps working without a network connection, and the layout is responsive so it stays usable on phones and tablets.

JSON to Dart / Flutter Model

Generate Dart model classes with fromJson and toJson from JSON.

Support

Works Offline

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No API

JSON input

Paste an API response to generate Flutter model classes

Root class name

Nullable fields

Uses String? style optional fields

json_serializable

Adds @JsonSerializable() and the import

Dart model

class Model {
  final int? id;
  final String? name;
  final double? score;
  final bool? active;
  final List<String>? tags;
  final Profile? profile;

  const Model({
    this.id,
    this.name,
    this.score,
    this.active,
    this.tags,
    this.profile,
  });

  factory Model.fromJson(Map<String, dynamic> json) => Model(
      id: json['id'] as int?,
      name: json['name'] as String?,
      score: json['score'] as double?,
      active: json['active'] as bool?,
      tags: (json['tags'] as List<dynamic>? ?? const []).cast<String>(),
      profile: json['profile'] == null ? null : Profile.fromJson(json['profile'] as Map<String, dynamic>),
      );

  Map<String, dynamic> toJson() => {
        'id': id,
        'name': name,
        'score': score,
        'active': active,
        'tags': tags,
        'profile': profile?.toJson(),
      };
}

class Profile {
  final String? city;
  final String? zip;

  const Profile({
    this.city,
    this.zip,
  });

  factory Profile.fromJson(Map<String, dynamic> json) => Profile(
      city: json['city'] as String?,
      zip: json['zip'] as String?,
      );

  Map<String, dynamic> toJson() => {
        'city': city,
        'zip': zip,
      };
}

About the JSON to Dart / Flutter Model

Paste any API response and get idiomatic Dart model classes for Flutter, complete with a const constructor, a fromJson factory, a toJson map, nested classes for nested objects and typed lists. Optionally emit null-safe fields or json_serializable annotations. Everything runs in your browser.

Examples

Simple object

{ "id": 1, "name": "Ada" }

Output

class Model { final int? id; final String? name; ... }

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

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Version 1.0.0 · Updated 2026-08-24 · Runs entirely in your browser