Convert JSON to Pydantic online, free. JSON is the dominant data-interchange format for web APIs and config. Pydantic BaseModels validate and parse data into typed Python objects. JSON to Pydantic conversion parses your JSON against the ECMA-404 / RFC 8259 grammar (https://www.rfc-editor.org/rfc/rfc8259), builds an in-memory model of its keys, nested objects and arrays, then emits ready-to-use Pydantic types as Pydantic BaseModel classes with typed fields following the Pydantic docs conventions. Processing runs in your browser in JavaScript with no upload or server round-trip — no size limit beyond your device's memory, so multi-megabyte documents convert in milliseconds and sensitive payloads never leave your machine. Typical uses include FastAPI request/response models, settings validation and ETL parsing.
It maps the full structure of your JSON onto idiomatic Pydantic types, following the Pydantic docs conventions. 100% free, no registration, and complete privacy — everything runs locally in your browser, so your data never touches a server.
Paste JSON and generate Pydantic types from Pydantic immediately. Conversion runs client-side, so there is no upload wait and large documents stay fast.
Nested JSON objects, tables and arrays are mapped faithfully onto Pydantic, including nested types and optional fields.
Your JSON never leaves your device — everything is processed locally in JavaScript, with nothing logged or stored.
Unlimited conversions with no account, no quotas, and no watermark. Works on desktop and mobile.
A JSON document and its Pydantic equivalent:
JSON input:
{
"title": "Dune",
"pages": 412,
"available": true
}Output:
from pydantic import BaseModel
class Book(BaseModel):
title: str
pages: int
available: boolPaste your JSON into the editor and press "Convert to Pydantic". The tool parses it against the ECMA-404 / RFC 8259 grammar, then generates Pydantic types following Pydantic docs conventions — instantly and entirely in your browser. You can validate or format the JSON first to be sure it is clean.
JSON already uses objects, arrays and typed scalars, so mapping to Pydantic is close to one-to-one: objects become types or structs, arrays become lists, and numbers, booleans and null keep their types.
Optional or nullable members in the generated Pydantic are inferred from keys missing in some records of your JSON, following Pydantic docs. Include the optional fields in your sample so they are typed correctly.
JSON (JavaScript Object Notation) (JSON) — JSON is the dominant data-interchange format for web APIs and config. Pydantic models (Pydantic) — Pydantic BaseModels validate and parse data into typed Python objects. This converter maps the structure of your JSON onto Pydantic so you can use it for FastAPI request/response models.
Yes. Invalid JSON is flagged with a clear error before anything is converted. Common JSON problems to check are matched braces and brackets, double-quoted keys, and no trailing commas. Starting from clean input keeps the generated Pydantic accurate.
Yes. The entire JSON-to-Pydantic conversion runs locally in your browser in JavaScript — your JSON is never uploaded, logged or stored. That matters when the data is something like REST/GraphQL API payloads, which should not leave your machine.
The generated Pydantic is ready for FastAPI request/response models, settings validation and ETL parsing. Copy or download it and drop it straight into your codebase.
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