Does it generate fromJson/toJson?

Yes — both factory constructors. The generated class round-trips JSON losslessly for the fields the sample documented.

Yes — assumes Dart 2.12+ sound null safety. Nullable fields (those sometimes missing in the sample) become `String?`, non-nullable become `String`.

What about deep nesting?

Each nested object becomes its own class. The tool names them by key (a `user` object becomes class `User`). Rename in your code to match your conventions.

Yes — the output is plain Dart with no Flutter-specific imports. Drop into any Flutter project.

JSON → Dart Class | DevTools Surf

DevTools Surf

Example: JSON → Dart Class

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

{"id":1,"name":"Flutter","stars":165000,"topics":["mobile","cross-platform"]}

Output

class Root {
  final int id;
  final String name;
  final int stars;
  final List<String> topics;

  Root({required this.id, required this.name, required this.stars, required this.topics});

  factory Root.fromJson(Map<String, dynamic> json) => Root(
    id: json['id'],
    name: json['name'],
    stars: json['stars'],
    topics: json['topics'],
  );

  Map<String, dynamic> toJson() => {
    'id': id,
    'name': name,
    'stars': stars,
    'topics': topics,
  };
}

About JSON → Dart Class

JSON → Dart Class preview - Converters tool

Generate a Dart class with fromJson/toJson from a JSON sample. Part of the DevTools Surf developer suite. Browse more tools in the Converters collection.

Use Cases

Flutter developers integrating REST APIs with type-safe models
Mobile teams sharing data classes between iOS and Android via Flutter
Dart backend developers building shelf or dart_frog server applications
Freelancers rapidly prototyping Flutter apps from existing API documentation

Tips

Generated classes include fromJson factory and toJson method for Flutter use
Nested JSON produces separate Dart classes with proper type references
Use the output with Flutter's http package for type-safe API calls

Fun Facts

Dart was originally launched by Google in 2011 as a replacement for JavaScript, but found its true success as the language behind Flutter starting in 2017.
Flutter's hot reload feature can reflect Dart code changes in under 1 second, making fromJson/toJson classes immediately testable during development.
Dart compiles to ARM machine code for mobile, JavaScript for web, and x86 for desktop — all from the same codebase and the same data classes.

FAQ

Does it generate fromJson/toJson?: Yes — both factory constructors. The generated class round-trips JSON losslessly for the fields the sample documented.
Null safety support?: Yes — assumes Dart 2.12+ sound null safety. Nullable fields (those sometimes missing in the sample) become `String?`, non-nullable become `String`.
What about deep nesting?: Each nested object becomes its own class. The tool names them by key (a `user` object becomes class `User`). Rename in your code to match your conventions.
Flutter-compatible?: Yes — the output is plain Dart with no Flutter-specific imports. Drop into any Flutter project.

Related Converters Tools

JSON to XML JSON to CSV JSON to YAML JSON to TSV JSON to String XML to JSON XML to CSV XML to String