JSON to TypeScript Converter
Paste any JSON object or array and instantly generate strongly-typed TypeScript interfaces with automatic type inference for strings, numbers, booleans, nested objects, and arrays. Choose between interface or type aliases, toggle strict null checks, enable JSDoc comments, and set a custom root interface name. Conversion runs entirely in your browser — no code or data is sent to a server.
JSON
Options
Code Style
TypeScript
What is JSON to TypeScript Converter?
Manually writing TypeScript interfaces for every API response is one of the most tedious parts of building a typed frontend. Paste the actual JSON response here and get correctly typed interfaces in seconds. The generator infers primitive types (string, number, boolean), detects optional fields when some array items are missing a key, produces array types, and creates separate named interfaces for nested objects — so the result is composable and reusable across your codebase. Fields that appear as null in the sample are typed as T | null. The generated interfaces work immediately with fetch, axios, React Query, and SWR response types, and serve as the input to Zod or Yup schema definitions for runtime validation. For teams adopting TypeScript incrementally, this tool is the fastest way to add type coverage to existing API integrations without rewriting models by hand.
How to Use
- 1
Paste Your JSON Sample
Paste a representative JSON object or array into the editor. Use a sample that contains all expected fields — optional fields should appear as null or with a representative value so the type generator can infer them correctly.
- 2
Configure Type Generation
Set the root interface name, choose between interface and type alias output, enable optional fields (?) for keys that may be absent, and select whether to generate separate named interfaces for nested objects.
- 3
Generate TypeScript Types
Click "Generate Types". The tool analyses value types across all array items to infer union types, detects optional fields, and produces correctly typed interfaces with nested type references.
- 4
Copy into Your Codebase
Copy the generated interfaces and paste them into your .ts or .d.ts file. Import the root type and use it to type API response variables, function parameters, and Zod/Yup schema definitions.
Common Use Cases
API Client Type Safety
Paste a REST API response and instantly generate TypeScript interfaces to type your fetch or axios calls, eliminating "any" types and enabling autocomplete in VS Code and other IDEs.
OpenAPI / Swagger Integration
When an OpenAPI spec is unavailable, generate TypeScript types directly from sample API JSON responses to bootstrap a typed client SDK without needing schema files.
Form & Validation Schema Generation
Derive TypeScript interfaces from your JSON data models to use as the basis for form validation schemas in libraries like Zod, Yup, or Joi, ensuring runtime and compile-time types stay in sync.
Legacy JS to TypeScript Migration
When migrating a JavaScript project to TypeScript, paste your existing JSON data structures to auto-generate interfaces and incrementally add type safety without rewriting models by hand.
Conversion Examples
API Response → TypeScript Interface
A JSON user object generates a typed interface with correct primitive types.
Input JSON
{
"id": 1,
"name": "Alice",
"email": "alice@example.com",
"isPremium": true,
"score": 98.5
}Output CSV
export interface Root {
id: number;
name: string;
email: string;
isPremium: boolean;
score: number;
}Nested JSON → Nested Interfaces
Nested objects generate separate named interfaces with cross-references.
Input JSON
{
"user": {
"id": 1,
"address": { "city": "London", "zip": "EC1A" }
},
"orders": [{ "id": 101, "total": 49.99 }]
}Output CSV
export interface Address {
city: string;
zip: string;
}
export interface User {
id: number;
address: Address;
}
export interface Order {
id: number;
total: number;
}
export interface Root {
user: User;
orders: Order[];
}