How does the tool decide a property is nullable?

When the JSON root is an array of objects, the tool compares the keys present across every item. Any key missing from at least one item, or any key whose value is null on at least one item, becomes a nullable property.

How does the tool name the Dart properties?

JSON keys are converted to camelCase, for example first_name becomes firstName. If the converted name differs from the original key, a comment above the property shows the original JSON key.

What Dart types does it use for numbers and strings?

Strings map to String, whole numbers map to int, decimal numbers map to double, and booleans map to bool.

How are nested objects and arrays handled?

Each nested object gets its own named class, generated from the property name, with its own fromJson/toJson pair. Arrays become List where T is inferred from the array elements.

Does the output include json_serializable or Freezed annotations?

No. The generated classes are plain Dart classes with hand-written fromJson/toJson methods and no external code-generation dependency. Add @JsonSerializable or convert to Freezed yourself if you prefer generated (de)serialization.

Is my JSON sent to a server?

No. Parsing and code generation run entirely in your browser with plain JavaScript. Your data never leaves your device.

JSON to Dart

Name: JSON to Dart
Availability: InStock
Author: Nham Vu

Paste JSON and instantly get matching Dart model classes with fromJson/toJson factories and nullable-safe fields.

Input JSON

Root class name

Use final fields (uncheck for mutable)

Dart Output

Paste JSON and click Generate

Copied!

Summary

Paste JSON and instantly get matching Dart model classes with fromJson/toJson factories and nullable-safe fields.

How it works

Paste or type JSON into the input panel, or load a sample.
Set a root class name (defaults to RootObject).
Click Generate to parse the JSON and build Dart model classes.
Nested objects become their own named classes; arrays of objects are scanned across all items to detect optional fields.
Fields that are missing from some items, or that hold null, become nullable properties.
Click Copy to copy the Dart code to your clipboard.

Use cases

Scaffold model classes for a REST API response before wiring up an http or dio call in Flutter.
Turn a sample config file into a typed Dart settings class.
Generate a starting model with fromJson/toJson without typing every field by hand.
Document a third-party API response shape as Dart types.
Check which fields are optional before writing null-handling logic by hand.
Speed up adding a new Flutter model from sample JSON during prototyping.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu