How to Convert JSON to TypeScript Interfaces Automatically

Why Convert JSON to TypeScript?

TypeScript interfaces give you compile-time safety when working with JSON from APIs. Without them, accessing a missing field silently returns undefined. With interfaces, TypeScript flags the error before you ship.

Manual Conversion

// JSON
{
  "id": 1,
  "name": "Alice",
  "email": "alice@example.com",
  "roles": ["admin", "user"]
}

// TypeScript Interface
interface User {
  id: number;
  name: string;
  email: string;
  roles: string[];
}

Handling Nested Objects

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

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

Optional Fields

interface User {
  id: number;
  name: string;
  email?: string;  // optional — may be undefined
  avatar: string | null;  // present but can be null
}

Using AI to Generate Interfaces

For large or nested JSON, generating interfaces manually is tedious. The JSON to TypeScript converter at jsondecode.com uses GPT-4o mini to generate accurate interfaces from any JSON in seconds.

Adding Runtime Validation with Zod

import { z } from 'zod';

const UserSchema = z.object({
  id: z.number(),
  name: z.string(),
  email: z.string().email().optional(),
});

type User = z.infer<typeof UserSchema>;

// Parse and validate at runtime
const user = UserSchema.parse(apiResponse);

Generate a Zod schema directly from JSON using the JSON to Zod converter →