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JSON to Dart Class

Generate Dart model classes with fromJson and toJson from a sample payload.

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With the methods included there is no build_runner step — the serialisation is written out in full.

Quick Tool Overview

The JSON to Dart Class converter writes Flutter-ready models: final fields, a const constructor with named parameters, and fromJson and toJson methods, all null safe without any build_runner step.

What it does
Generates Dart model classes with JSON serialisation
You give it
A JSON payload, ideally an array of records
You get back
Null-safe classes with fromJson and toJson written out
Best for
Flutter apps consuming a REST API
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About the JSON to Dart Class

Flutter has no reflection, so every model needs its serialisation written out by hand — which is exactly the boilerplate this generates. Each class gets final fields, a const constructor with named parameters, a fromJson factory and a toJson method.

Null safety is handled properly rather than by making everything nullable. A field present in every record is non-nullable and marked required in the constructor; one that is sometimes missing gets a question mark and is optional. Nested objects call their own fromJson, and lists of objects map over the elements with the right cast, so the generated code compiles against a null-safe SDK without edits.

Key features of the JSON to Dart Class

Serialisation already written

fromJson and toJson are generated in full, so there is no code-generation step and no build_runner to keep in sync.

Real null safety

Fields present in every record are non-nullable and required; the rest are nullable and optional. It compiles against Dart 2.12 and later unchanged.

Immutable by default

Final fields and a const constructor, which is what lets Flutter skip rebuilding widgets whose inputs have not changed.

Nested lists handled

A list of objects maps over its elements with the right cast and the element type's fromJson — the pattern the Dart team documents.

Plain-data mode

Skip the methods entirely if you do use a code generator and only want the field declarations.

How to use the JSON to Dart Class

  1. 1

    Paste the JSON

    A real API response is ideal; an array detects optional fields.

  2. 2

    Name the root class

    Nested classes are named from the keys that hold them.

  3. 3

    Choose the methods

    Keep fromJson and toJson, or generate plain data classes if you use a code generator instead.

  4. 4

    Copy into your project

    Paste into a .dart file under lib/models.

Frequently asked questions

No. The point of this output is that the serialisation is already written, so there is no build_runner step. Use json_serializable instead when you have dozens of models and want them regenerated on every schema change.

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