JSON to TypeScript Interface Generator

How to Generate TypeScript Interfaces from JSON

What Are TypeScript Interfaces?

interface User {
  id: number;
  name: string;
  email: string;
  isActive: boolean;
  address: Address;
}

interface Address {
  street: string;
  city: string;
  zip: string;
}

How the Generator Works

Generated Interface Examples

{
  "id": 42,
  "name": "Alice",
  "active": true
}

interface Root {
  id: number;
  name: string;
  active: boolean;
}

[
  { "id": 1, "name": "Alice", "role": "admin" },
  { "id": 2, "name": "Bob" }
]

// Top-level JSON is an array: Root[]

interface Root {
  id: number;
  name: string;
  role?: string;
}

{
  "user": {
    "id": 1,
    "address": {
      "city": "New York"
    }
  }
}

interface Root {
  user: User;
}

interface User {
  id: number;
  address: Address;
}

interface Address {
  city: string;
}

Limitations to Be Aware Of

• ⚠Single sample: Inference is based on the values in the JSON you provide. If an API sometimes returns a field and sometimes omits it, use multiple samples or mark the field optional manually.
• ⚠Null widens to null only: A field that is null in the sample gets type null. If the field can also be a string in other responses, change it to string | null manually.
• ⚠No integer vs float distinction: JSON numbers — whether integers or decimals — all map to number in TypeScript since JavaScript makes no distinction.
• ⚠Enum detection: String fields that are actually enums (e.g., "status": "active") generate as string. Narrow them to a union type or enum manually if needed.