JSON to TypeScript Interface

Paste a JSON sample and get TypeScript interfaces, with nested objects, arrays, optional fields and union types worked out for you.

Root name Add export

JSON

TypeScript

Convert JSON to TypeScript Interfaces

Writing TypeScript types for an API response by hand is slow. Paste a sample of the JSON and this tool infers the interfaces for you.

Nested objects become their own interfaces, arrays of objects are merged into one, fields that are missing in some items become optional, and mixed values become union types.

Key features

Nested objects as separate, named interfaces
Arrays of objects merged, with optional fields where items differ
null and union types
Choose the root name and whether to add export

Example output

export interface User {
  id: number;
  name: string;
  address: Address;
}

export interface Address {
  city: string;
}

How to use

Paste a JSON sample.
Set the root name, for example User.
Copy the interfaces into your project.

Use cases

Typing API responses
Creating models from sample data or fixtures
Starting a type definition for a config file

Frequently Asked Questions (FAQ)

How are types inferred?+

From the values in your sample. A sample cannot show every possible value, so review the result, especially for null and optional fields.

How are arrays handled?+

All objects in an array are merged into one interface. A property that is missing from some of them is marked optional.

What about keys that are not valid identifiers?+

They are quoted, for example "first-name": string.

Is my JSON uploaded?+

No. It stays in your browser.