JSON to TypeScript

The Tool Every TypeScript Dev Uses Weekly

You’re integrating with a new API. The docs are sparse, but you’ve got a sample response. You need TypeScript interfaces so your IDE stops screaming about any types and actually gives you autocomplete. Writing the interfaces by hand from a 30-field nested JSON object? Life’s too short.

Paste the JSON, get interfaces. The tool recursively analyzes every value — strings, numbers, booleans, nulls (marked as optional with ?), arrays, and nested objects. Each nested object becomes its own named interface, keeping things modular and clean.

What It Produces

{"name": "John", "age": 30, "address": {"city": "NYC", "zip": "10001"}} becomes:

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

interface Root {
  name: string;
  age: number;
  address: Address;
}

Null values get the ? optional modifier. Arrays are typed from their first element. Nested objects become separate named interfaces.

The Workflow That Saves Hours

Step 1: Hit the API in Postman or your browser’s network tab. Copy the JSON response.

Step 2: Paste it here. Get interfaces.

Step 3: Drop the interfaces into your types.ts file. Rename Root to something meaningful like UserResponse.

Step 4: Refine. The tool infers generic types — you might want to tighten string to a literal union ('active' | 'inactive'), or add readonly modifiers, or replace any with a concrete type.

Where This Fits

React/Next.js data fetching. Your useEffect calls an API. Without types, you’re working with any and hoping for the best. Generate the interface, type your state, and get autocomplete on every field.

API client SDKs. You’re building a typed wrapper around a REST API. Paste each endpoint’s response, generate the interface, and export it from your SDK.

Zod companion. Generate interfaces here for compile-time safety, then use the JSON to Zod converter to create runtime validation schemas from the same JSON. Types at build time, validation at runtime.

Multi-language projects. Same JSON, different language? The JSON to Go Struct and JSON to Python Dataclass converters produce equivalent type definitions for Go and Python.

Works with React, Next.js, Vue, Angular, Node.js — any TypeScript environment. All conversion runs in your browser, and your data stays private.