BYTETOOLS

JSON to Dart Converter

Convert JSON to null-safe Dart classes online, with generated fromJson and toJson methods, typed List<T> fields and nested classes — in your browser.

What is the JSON to Dart Converter?

The ByteTools JSON to Dart Converter turns a sample JSON document into null-safe Dart classes complete with fromJson factory constructors and toJson methods.

  • Null-safe types with ? for nullable and optional keys
  • fromJson factory and toJson method generated per class
  • Typed lists with element casts, including lists of objects
  • Nested classes named from their JSON keys
  • num-to-double handling so integer values decode into double fields
  • 100% private — JSON never leaves your browser

How to use the JSON to Dart Converter

  1. 1

    Paste a JSON sample into the input box.

  2. 2

    Set the root class name.

  3. 3

    Click Generate Dart to build the classes with fromJson and toJson.

  4. 4

    Copy the code or download it as a .dart file.

About the JSON to Dart Converter

The ByteTools JSON to Dart Converter turns a sample JSON document into null-safe Dart classes complete with fromJson factory constructors and toJson methods. Fields are typed from the actual values — int, double, bool, String, List<T> — nested objects become their own classes, and nullable or optional keys get Dart's ? types with the matching null-aware parsing code.

It is built for Flutter and Dart developers who want typed models without adding build_runner and code generation to a small project. The output mirrors the style of json_serializable: named constructor parameters marked required when non-null, explicit casts in fromJson, and toJson emitting the original JSON keys.

Everything is computed 100% locally in your browser using JavaScript. The JSON you paste is never uploaded or stored, making the tool safe for private API responses and unreleased app data.

Frequently asked questions

How do I generate Dart classes from JSON?

Paste a JSON sample, name the root class and click Generate Dart. Each object shape becomes a class with typed final fields, a fromJson factory that casts each value, and a toJson method that writes the original JSON keys back out.

Does the generated code work with Flutter?

Yes. The output is plain Dart with no dependencies, so it drops into any Flutter or server-side Dart project. Decode with MyClass.fromJson(jsonDecode(body) as Map<String, dynamic>).

How is null safety handled?

Fields that are null in the sample, or missing from some array elements, get nullable types like String? and null-aware parsing such as (json['x'] as num?)?.toDouble(). Non-nullable fields become required constructor parameters.

Why do double fields parse with (as num).toDouble()?

In Dart, jsonDecode turns 5 into an int and 5.5 into a double. Casting through num and calling toDouble() means a field typed as double will not crash when the API happens to send a whole number.

Is this the same as json_serializable?

The output follows the same conventions, but it is generated once from your sample rather than kept in sync by build_runner. For quick models it saves the tooling setup; for large evolving APIs a code-gen pipeline may still be worth it.

Is my JSON kept private?

Yes. The converter runs entirely in your browser — nothing is uploaded, logged or stored anywhere.

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