JSON to TypeScript interface

How to use it

1. Enter json input and root type name.
2. The result appears straight away and updates as you edit.
3. Copy the result, or copy a link that keeps the same values to share it.

How it is calculated

string for text, number for every number, boolean for true/false, T[] for lists, and each nested object becomes its own interface. When array items are merged, a key missing from some items becomes optional (?), null adds | null, and a key that is only ever null becomes unknown.

Example

Inputs: Root type name = Root. Result: Generated code: export interface Root { id: number; name: string; email: string; is_active: boolean; balance: number; tags: string[]; address: Address; orders: Order[]; } export interface Address { city: string; postal_code: string; } export interface Order { order_id: string; total: number; coupon: string | null; }; Types generated: 3; Fields: 13.

{
  "id": 1024,
  "name": "Sara Ahmed",
  "email": "sara@example.com",
  "is_active": true,
  "balance": 1520.75,
  "tags": ["vip", "riyadh"],
  "address": { "city": "Riyadh", "postal_code": "12211" },
  "orders": [
    { "order_id": "A-1", "total": 99.5, "coupon": "EID10" },
    { "order_id": "A-2", "total": 120, "coupon": null }
  ]
}

export interface Root {
  id: number;
  name: string;
  email: string;
  is_active: boolean;
  balance: number;
  tags: string[];
  address: Address;
  orders: Order[];
}

export interface Address {
  city: string;
  postal_code: string;
}

export interface Order {
  order_id: string;
  total: number;
  coupon: string | null;
}

Limits and caveats

• Types come from the sample only, so a key that never appears is not generated.
• A key holding different types, such as text in one item and a number in another, becomes unknown.