JSON to TypeScript Interface Generator

Input

Output

Ready

Ln 1, Col 1

Convert JSON to TypeScript in one step

Paste an API response or config file and get TypeScript interfaces that describe it, so your editor can autocomplete and type-check the data instead of treating it as any.

How to use it

Paste a JSON sample into the Input panel, open a file, or drop it onto the page. A sample is already loaded so you can see the result.
The TypeScript code appears instantly in the Output panel and updates as you type.
Rename the top-level type under Settings → Root type name, and use Sort keys to order fields alphabetically.
Copy the code or Download it as Root.ts.

What the TypeScript generator produces

An export interface for every object shape; nested objects get their own named interface (for example users becomes User).
Keys missing from some array items become optional with ?.
Mixed arrays become union types such as (string | number)[].
Keys that are not valid identifiers are quoted; identical shapes are reused instead of duplicated.

Using the generated TypeScript code

Save the interfaces to a file and use them to type parsed data:

import type { Root } from './types';

const res = await fetch('/api/data');
const data: Root = await res.json();
console.log(data.users[0].name);

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JSON to TypeScript FAQ

Does it generate types or interfaces?

Interfaces for every object, plus a type alias when the top-level value is an array or a primitive.

How are optional properties detected?

If a key appears in some objects of an array but not in others, it is marked optional with ?. Values that are sometimes null get a | null union.

Is my data uploaded to a server?

No. The JSON to TypeScript runs entirely in your browser using JavaScript. Your data is never uploaded, logged or stored, and the tool keeps working offline after your first visit.