JSON to TypeScript Interface Generator

Typed models from real data

Writing interfaces by hand for a large API response is slow and error-prone. This generator reads your JSON and produces TypeScript declarations that match it. Unlike simple converters that only look at the first element of an array, it merges every element: if a property exists in some objects but not others it becomes optional (archived?: boolean), and if a property holds different kinds of values it becomes a union (string | null).

Nested objects get their own named interfaces (derived from the property name, e.g. profile → Profile, projects → Project), and identical shapes are reused instead of being duplicated.

How to use it

1. Paste a representative JSON sample — the more array items it contains, the more accurate the optional fields will be.
2. Set the root type name, choose interface or type, and toggle export / readonly.
3. Copy the result into a .ts file or download it.

Example

{
  "id": 1,
  "tags": ["a"],
  "items": [
    {"sku": "A", "qty": 1},
    {"sku": "B", "qty": 2, "note": "gift"}
  ]
}

export interface Root {
  id: number;
  tags: string[];
  items: Item[];
}

export interface Item {
  sku: string;
  qty: number;
  note?: string;
}

Type mapping

Dates arrive in JSON as strings, so they are typed as string. Convert them to Date in your code if needed.