JSON to TypeScript — Instant Interface Generator

JSON to TypeScript is a free browser-based tool that converts any JSON object or array into clean, production-ready TypeScript interfaces or type aliases in real time. No backend, no login, no friction.

The Problem

Every TypeScript developer knows the routine: you get a new API response back, paste the JSON into your editor, and then spend the next ten minutes manually writing out interfaces. You type interface User {, enumerate every key, guess whether nested objects need their own types, debate optional vs required, and eventually end up with something that mostly works — until the API changes.

It's tedious, error-prone, and a solved problem. You shouldn't be writing TypeScript boilerplate by hand in 2026.

How It Works

Paste JSON, Get TypeScript

Open the tool, paste any JSON into the left panel, and TypeScript interfaces appear instantly on the right. The conversion is live — it updates as you type.

{
  "id": 1,
  "name": "Alice Johnson",
  "email": "alice@example.com",
  "isActive": true,
  "address": {
    "street": "123 Main St",
    "city": "San Francisco"
  },
  "orders": [
    { "orderId": "ORD-001", "total": 149.99, "shipped": true }
  ]
}

Becomes:

export interface Order {
  orderId: string;
  total: number;
  shipped: boolean;
}
 
export interface Address {
  street: string;
  city: string;
}
 
export interface Root {
  id: number;
  name: string;
  email: string;
  isActive: boolean;
  address: Address;
  orders: Order[];
}

Flexible Options

Four toggles give you full control over the output:

• Interface vs Type Alias — Switch between interface Foo {} and type Foo = {} with a single click
• Export Types — Prefix every type with export for module-ready output
• Optional Properties — Mark properties as optional (key?: Type) when working with partial objects
• Readonly — Add readonly to every property for immutable type definitions

You can also set a custom root interface name — handy when the default "Root" doesn't match your domain model.

Nested Object Extraction

Nested JSON objects are automatically extracted into separately named interfaces. The naming uses PascalCase derived from the property key: address → Address, userProfile → UserProfile. This produces clean, idiomatic TypeScript rather than deeply nested inline types.

Array Type Inference

Arrays of primitive values generate typed arrays (string[], number[]). Arrays of objects generate a named interface for the element type and return a typed array reference. Arrays with mixed types produce union types: (string | number)[].

Copy to Clipboard

One click copies all generated TypeScript to the clipboard. Paste directly into your .ts file.

Key Features

• Real-time conversion — No submit button, output updates as you edit the JSON
• Nested object support — Extracts sub-interfaces automatically with PascalCase naming
• Union type inference — Mixed-type arrays become proper union types
• Optional property detection — Marks optional keys when processing object arrays
• Interface & type alias output — Switch between both with a toggle
• Export keyword — Makes output paste-ready for module files
• Readonly modifier — For immutable type definitions
• Custom root name — Rename the top-level interface
• 100% client-side — Your JSON never leaves the browser

Technical Implementation

• Next.js 16 with App Router
• TypeScript strict mode — the converter itself is fully typed
• Tailwind CSS v4 with OKLCH color tokens
• shadcn/ui components
• Framer Motion for UI animations
• Zero external API calls — pure browser logic

Use Cases

TypeScript Developers

Stop writing interface boilerplate for every API response. Paste the response JSON and get ready-to-use types.

Frontend Engineers

Working with a REST API that has no TypeScript SDK? Generate your own type definitions instantly from the actual JSON payloads.

Full-Stack Teams

Quickly create shared types from database records, webhook payloads, or configuration objects.

API Documentation

Generate type definitions that serve as lightweight API documentation. Clear, readable interfaces communicate the shape of your data better than raw JSON.

Try it now: json-to-typescript.tools.jagodana.com