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JSON to Python Classes

Turn a JSON sample into Pydantic models or dataclasses.

Root name: Mark missing keys optional

How to Use

Paste the JSON into the left box.
Python (Pydantic) is already chosen; switch to Python (dataclass) if you prefer.
Set the Root name for the top-level class.
Copy the classes into your code.

Frequently Asked Questions

Pydantic or dataclass?

Pydantic validates and converts data when it loads it, which suits API input. Dataclasses are plain containers from the standard library with no validation.

What happens to keys like firstName or 2nd key?

Fields are renamed to snake_case. Pydantic keeps the original key with Field(alias=...); dataclasses get a comment naming it.

Which Pydantic version is it for?

The models use BaseModel and Field in a way that works with Pydantic 2 and also with version 1.

Is my JSON sent anywhere?

No. Everything happens in your browser.

Generate Python Classes from JSON

Updated September 30, 2026 · By Saman

Typed models make API data easier to work with and catch mistakes early. This page opens JSON to Types with Pydantic chosen, and dataclasses one click away.

Types used

Values map to str, int, float, bool and List[...]. Fields that are missing or null in the sample become Optional[...] with a default of None.

Related tools

To validate the same data with any language, generate a JSON Schema. To convert the JSON to YAML or CSV, use the JSON converter.

Guides

How to Type an API Response in TypeScript fetch gives you data typed as any, which switches TypeScript off exactly where bugs come from. Here is how to give API data a real type, quickly and safely.

JSON to Python Classes

Generate Python Classes from JSON

Types used

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