JSON to TypeScript Interface

Convert JSON into TypeScript interfaces or type aliases instantly. Handles nested objects, arrays, unions, and optional keys. Free, runs in your browser.

Root type name

Output

Treat null as optional

JSON sample

TypeScript

export interface User {
  id: number;
  name: string;
  email: null;
  roles: string[];
  posts: Post[];
}

export interface Post {
  id: number;
  title: string;
  draft?: boolean;
  tags?: string[];
}

Frequently asked questions

How are optional fields detected?

When an array contains objects, keys missing from some items are marked optional with ?.

What happens with null values?

By default null becomes part of a union type. Turn on 'Treat null as optional' to mark those keys optional instead.

Interface or type?

Both work for object shapes. Interfaces can be extended and merged; type aliases can express unions.