JSON to Dart Converter

Convert JSON to Dart model classes

JSON to Dart conversion is useful when an application receives structured data and you want Dart classes to represent that data in a more organised way. Instead of typing every field and conversion method manually, provide a representative JSON object and generate a starting set of model classes. The output is intended to help you work with decoded data in Dart projects; it is not a complete description of every response an application might return.

How to generate the Dart code

1. Paste a JSON object into the input box, or select a local .json file.
2. Enter a root class name such as User or ApiResponse. Use a clear class name that starts with a letter.
3. Select Generate Dart, then inspect the generated code. Copy it or download the resulting .dart file when it looks suitable.

Choosing a file only loads its text into the editor. You must run Generate Dart after loading or editing the input. If the input changes, generate the code again to avoid using an outdated result. The sample button provides a small example containing scalar values, a nested object, and a list, so you can see how different JSON shapes are represented.

What the generated classes contain

The converter infers field types from the values present in your sample. Text values become String, whole numbers become int, decimal numbers become double, and true or false values become bool. Nested objects can produce additional classes, and a list containing objects can produce a list of the inferred class. Empty lists and null values do not provide enough information to infer a specific item type, so the output may use dynamic in those cases.

Generated classes include fields and fromJson/toJson helpers. These helpers provide a useful starting point for converting between a JSON map and a Dart object. Review the class and field names, especially when source keys contain spaces, punctuation, abbreviations, or names that are not valid Dart identifiers. The generated property name may be adjusted to form a usable identifier while the JSON key remains the original key.

Why a representative sample matters

A JSON example only shows one possible response. If a field is absent in another response, has a different type, or changes from a number to a string, the generated code may need changes. For example, a field that is always an integer in your sample might arrive as null in a real response. Likewise, an empty list does not reveal whether future items will be strings, numbers, or objects. Include realistic examples and compare the generated model with actual data.

Errors and practical checks

JSON syntax must be valid before Dart classes can be generated. Check that property names and string values use double quotes, commas separate properties correctly, and braces and brackets are balanced. A trailing comma or an unquoted property name can prevent parsing. The root must be an object or an array containing at least one object so the converter has fields to infer; a simple number or string alone cannot define a model class.

After generation, run the code in your project and test it against representative responses. Pay special attention to nullable fields, lists, nested objects, and fields whose values may be missing. You may need custom handling for dates, enums, union-shaped values, or API-specific rules. This converter generates code from the supplied sample; it does not connect to your service or verify its schema. Processing happens in your browser, so the JSON you paste or select is not uploaded to DataFrog.