JSON → TypeScript

Paste any JSON; **live-infer TypeScript types** — auto-named nested types (`users → User`), shape-merging across array elements, optional-field detection, mixed-type arrays as unions. Choose interface vs type, root name, and `readonly`. Runs entirely locally — no upload.

FormatRoot namereadonly

JSON

TypeScript

export interface Root {
  id: string;
  user: User;
  posts: Post[];
  metadata: null;
}

export interface User {
  name: string;
  age: number;
  active: boolean;
  tags: string[];
}

export interface Post {
  title: string;
  likes: number;
  draft?: boolean;
}

›How to use

Paste any JSON on the left (API response, config file, fixture — anything).
TypeScript interface / type is generated instantly with smart nested-type naming (e.g. User_Address).
Array with mixed-shape elements? Shapes are merged and optional is auto-marked.
Toggle readonly and type vs interface at the top, then copy into your SDK / model file.

Tips

Want JSDoc comments? Add a _doc field in your JSON — it gets attached to the generated type.
Null values in the API response become T | null — never silently dropped.

JSON → TypeScript

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