Data & Developer

JSON to Dart Class Generator

Generate Dart classes from JSON payloads.

Files never leave your device — all processing is in-browser.

Generated Dart

class Model {
  final int? id;
  final String? name;
  final String? email;
  final Address? address;
  final List<String>? tags;

  Model({
    this.id,
    this.name,
    this.email,
    this.address,
    this.tags,
  });

  factory Model.fromJson(Map<String, dynamic> json) {
    return Model(
      id: json['id'] as int?,
      name: json['name'] as String?,
      email: json['email'] as String?,
      address: json['address'] == null ? null : Address.fromJson(json['address'] as Map<String, dynamic>),
      tags: (json['tags'] as List?)?.cast<String>(),
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'name': name,
      'email': email,
      'address': address?.toJson(),
      'tags': tags,
    };
  }
}

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

  Address({
    this.city,
    this.zip,
  });

  factory Address.fromJson(Map<String, dynamic> json) {
    return Address(
      city: json['city'] as String?,
      zip: json['zip'] as String?,
    );
  }

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

Paste a JSON sample and get idiomatic Dart classes with fromJson and toJson serialization, ready to drop into your Flutter project. Nested objects and arrays are turned into nested classes automatically.

See also: JSON to Go Struct, JSON to SQL, JSON to Excel.

How to use the JSON to Dart tool

  1. STEP 1

    Paste a JSON sample (a single object works best).

  2. STEP 2

    Set a root class name.

  3. STEP 3

    Copy or download the generated Dart file.

What is JSON to Dart?

JSON to Dart is a free online converter that turns JSON files into Dart files directly in your browser. It is designed as a fast, zero-friction alternative to installing desktop software or trusting your files to an anonymous upload server.

FameConvert runs entirely in your browser. There is no signup, no queue, no watermark and no ten-file daily limit — the whole tool loads once and then works offline. Because the conversion happens on your device, output files are ready the moment the browser finishes processing.

Why use JSON to Dart?

Most online converters require you to upload the file to a random server, sit through an ad-heavy queue and then download a watermarked result. JSON to Dart takes the opposite approach:

  • Preserves the source — your original JSON file is untouched, so you can convert as many times as you like.
  • 100% private — files are processed on your device and never uploaded to a server.
  • Free forever — no accounts, no watermarks, no size caps and no hidden usage limits.
  • Instant results — output downloads the moment the browser finishes; no waiting in a queue.
  • Works offline — once the page has loaded, the tool keeps working without a network connection.
  • No install — nothing to download, update or hand admin rights to; any modern browser is enough.

Key features

  • Drag-and-drop upload with instant client-side validation for file type and size.
  • Batch support — process multiple files in one go, then download them individually or as a ZIP.
  • Clear file-size and MIME-type checks so you know immediately if a file is not supported.
  • Built-in conversion history so you can re-download recent results without repeating the work.
  • Shareable links that preserve your tool settings, perfect for teammates and support requests.
  • Responsive design that works equally well on desktop, tablet and mobile browsers.

When JSON to Dart is useful

  • Generate typed Flutter model classes from an API sample in seconds.
  • Prepare files for email attachments, client hand-offs or CMS uploads that only accept certain formats.
  • Archive assets in a lossless, widely-supported format so they remain readable years from now.
  • Batch-convert an entire folder before importing into another application.
  • Convert on a locked-down work laptop where installing new desktop software is not allowed.
  • Handle sensitive documents that must never leave the device for compliance reasons.

About the formats

JSON (JavaScript Object Notation) — JSON is the default data-exchange format of the modern web. Its lightweight, human-readable structure of objects and arrays maps directly to programming language types, which is why virtually every API speaks JSON.

Dart (Dart class definitions) — Dart is the language behind Flutter. Strongly-typed model classes with fromJson / toJson boilerplate are the backbone of every Flutter app that talks to a REST or GraphQL API.

  • Best of JSON: Human-readable, Native to JavaScript, Supported everywhere.
  • Best of Dart: Type-safe Flutter models, Null safety built in.

Tips for the best results

  • Convert on a modern browser (Chrome, Edge, Firefox, Safari) for the fastest results — old browsers lack some of the underlying APIs.
  • For very large batches, close other heavy tabs so the browser can dedicate more memory to the conversion.
  • Keep an original copy of your source file until you have opened the output and confirmed it looks correct.

Is it private and safe?

Yes. JSON to Dart is a fully client-side tool. When you drop a file into the upload area it is decoded in your browser's memory, converted with JavaScript running on your device, and the result is offered as a direct download. No copy of the file is sent to FameConvert, uploaded to cloud storage or logged in a database — you can even switch off your network after the page loads and the tool will continue to work.

This makes FameConvert a good fit for legal contracts, medical scans, financial statements, ID documents and any other file you would not want passing through an unknown server.

Frequently asked questions

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