Paste a JSON payload and instantly generate TypeScript interfaces, Python dataclasses, or Go structs — no server, no uploads.
This free online tool turns a sample JSON payload — an API response, a webhook body, a config file — into ready-to-use typed code. Paste your JSON, click Generate, and pick a language tab to get a TypeScript interface, a Python dataclass, or a Go struct that matches the exact shape of your data, including nested objects, arrays, and optional fields.
Hand-typing interfaces for a deeply nested API response is slow and error-prone — a single typo in
a field name silently breaks type safety. This tool infers field types (string, number, boolean,
nested object, array), detects fields that are missing or null in some sample records
and marks them optional or nullable, and generates consistent naming for nested types automatically.
All analysis happens entirely in your browser using JavaScript. Your JSON is never uploaded to a server, which makes this safe to use with real API responses and internal payloads.
Different languages express the same JSON shape differently. Here is what this tool generates for a simple JSON object, and what to expect from each output format.
Nested objects become named interface declarations. Arrays become Type[]. Fields that are missing in some sample records become optional (field?: string); fields that were null become nullable (string | null).
Generates @dataclass classes with type hints from typing (Optional, List, Any). Nested classes are declared before the classes that use them, so the output runs as-is.
Field names are converted to exported PascalCase Go identifiers with matching json:"..." tags so encoding/json unmarshals correctly. Nullable fields use pointer types.
Works with deeply nested objects, arrays of objects with inconsistent fields, mixed number types, and null values — the common shape of real API responses, not just toy examples.
Generate TypeScript interfaces directly from a real API response so your React, Vue, or Angular components are type-safe from day one — no guessing at the shape of the data.
Turn sample JSON payloads (webhooks, third-party API responses, log events) into Python dataclasses for validation, serialization, or documentation.
Skip manually writing struct definitions and json tags for every new API integration — paste the response body and get a working struct instantly.
Working against a third-party API with no published SDK or types? Paste an example response and generate a starting point in your language of choice.
If your JSON is an array of objects and a key is missing from some of the objects, the generated field is marked optional. If a key's value is null in at least one sample, the field is generated as nullable (e.g. string | null in TypeScript, Optional[str] in Python). For a single object with no array of examples, every present key is treated as required.
Yes. Nested objects at any depth become their own named type (interface, dataclass, or struct), named after the parent key. Arrays of nested objects are analyzed element by element and merged into a single type.
The tool merges the shape of every item in the array. Fields present in some items but not others become optional. If the same field has different primitive types across items (e.g. sometimes a number, sometimes a string), it falls back to any / Any / interface{} for that field.
No. All parsing and code generation happens locally in your browser with JavaScript. Nothing is sent to a server, which makes this safe to use with real, sensitive API responses.
Yes — use the dedicated JSON Schema Generator to produce a JSON Schema document (Draft 2020-12 or Draft-07) from the same kind of sample payload.
Built by Deepak Kumar — a developer who wanted a JSON tool that respects your privacy. All processing happens in your browser. Your data never leaves your device.