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JSON to Types

Turn a JSON sample into TypeScript interfaces, Go structs, Python models, C# classes, Rust structs or a JSON Schema.

Root name: Mark missing keys optional

How to Use

1. Paste JSON into the left box, for example an API response, or press Sample.
2. Choose the Output: TypeScript, Go, Python (Pydantic), Python (dataclass), C#, Rust (serde) or JSON Schema.
3. Set the Root name for the top-level type. For TypeScript, choose interface or type.
4. Keep Mark missing keys optional on to make fields that are missing from some array items optional.
5. Copy the generated code.

Nested objects become their own named types, and identical shapes share one type. Everything runs in your browser.

Frequently Asked Questions

How are optional and nullable fields detected?

From the sample itself. In an array of objects, a key that appears in some items but not others becomes optional, and a value that is null in one item makes the field nullable.

Why is a field typed as unknown or Any?

Its values had different types in the sample, such as a number in one item and a string in another, or it was always null. Check the API documentation and set the type by hand.

How are nested objects named?

After their key in PascalCase, and items of an array after the singular of its key, so orders gives Order. Objects with the same shape reuse one name.

Is the JSON sent to a server?

No. The types are generated in your browser, so API responses with real data stay on your device.

How reliable is a type made from one sample?

It is only as complete as the sample. Paste a response that contains every field, or an array with several varied items, for the most accurate types.

JSON to Types - TypeScript, Go, Python, C#, Rust and JSON Schema

Updated September 30, 2026 · By Saman

Paste a JSON sample, such as a response from an API, and get the type definitions to go with it: TypeScript interfaces, Go structs with JSON tags, Pydantic models or dataclasses, C# classes, Rust structs for serde, or a JSON Schema. Nested objects become their own named types, so the result reads like code a person would write.

API responses often contain real customer data, tokens and internal IDs. The conversion runs entirely in your browser, so none of it is sent anywhere.

How to use it

Paste JSON into the left box, or press Sample to see an example.
Choose the Output language.
Set the Root name of the top-level type; for TypeScript, choose interface or type.
Copy the result into your project.

How the types are worked out

Numbers become integers when every value is whole, and floating-point otherwise: 42 and 18.5 in the same field give a float.
Arrays of objects are merged: every key seen in any item appears in the type.
Optional fields: with Mark missing keys optional on, a key missing from some items becomes optional (coupon?: string, omitempty, Option, = None).
Nullable fields: a value that is null in one item makes the field nullable, for example string | null or *string in Go.
Mixed types, such as a number in one item and a string in another, give unknown, Any or interface{}, so you can decide by hand.
Names come from the keys: address gives Address, and the items of orders give Order. Objects with the same shape share one type.

Per language

Output	What you get
TypeScript	`export interface` or `export type`; keys that are not valid names are quoted
Go	Exported structs with `json` tags, `int64` and `float64`, and common initialisms such as `ID` and `URL`
Python (Pydantic)	`BaseModel` classes; snake_case fields with `Field(alias=...)` when the JSON key differs
Python (dataclass)	`@dataclass` classes, with optional fields placed last as dataclasses require
C#	Classes with `[JsonPropertyName]` for System.Text.Json, `long`, `double` and `List<T>`
Rust	Structs deriving `Serialize` and `Deserialize`, with `#[serde(rename)]` where needed
JSON Schema	A draft 2020-12 schema with `required` lists, ready for validators

Get the most accurate types

A type is only as complete as the sample it came from. Use a response that includes every optional field at least once, and paste an array with several different items rather than one, so the merging can see which fields vary. Dates arrive in JSON as strings and stay strings; convert them in your code where you need real date types.

Related tools

To tidy or validate the JSON first, use the JSON formatter. To turn it into YAML, CSV or XML, use the JSON converter. The task pages open this tool with a language chosen: JSON to TypeScript, JSON to Go, JSON to Python, JSON to C# and JSON Schema generator.

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.