JSON to TypeScript Type Generator
Generate clean TypeScript interfaces and type declarations from single or multiple sample JSON payloads with optional/nullable field merging.
export interface Address {
street: string;
city: string;
postalCode: number;
country: string;
}
export interface Metadata {
lastLogin: string;
loginCount: number;
}
export interface User {
id: number;
name: string;
email: string;
role: string;
verified: boolean;
address: Address;
tags: string[];
metadata: Metadata;
}JSON to TypeScript Type Generator
Generate clean TypeScript interfaces and type declarations from sample JSON.
Overview
The JSON to TypeScript Type Generator analyzes JSON objects, nested trees, and arrays of heterogeneous sample payloads to generate clean, idiomatic TypeScript interfaces or type aliases. It intelligently distinguishes missing properties (marking them optional with "?") from explicit null values ("| null"), quotes non-identifier property keys, infers union types for heterogeneous array elements, and extracts nested objects into modular sub-interfaces.
How to Generate TypeScript Types from JSON
Input a single JSON object or an array of sample records (e.g. API responses) to analyze shape variations across multiple entries.
Customize the root interface name (e.g. "User", "ApiResponse"), choose between "interface" or "type alias" syntax, and toggle the "export" keyword prefix.
Inspect the generated TypeScript declarations. Missing fields across records are automatically marked optional, nullable values are typed with "| null", and nested objects are extracted into clean child interfaces.
Copy the TypeScript code to your clipboard or download it as a ready-to-use .d.ts definition file for your project.
[{"id": 1, "name": "Alice", "bio": "Writer"}, {"id": 2, "name": "Bob", "bio": null}, {"id": 3, "name": "Charlie"}]export interface User {
id: number;
name: string;
bio?: string | null;
}Because "bio" was string in sample 1, null in sample 2, and missing in sample 3, the generator correctly combines optionality (?) and nullability (| null).
- Local Execution: Evaluates JSON structures purely in-browser with zero network calls.
- Union Handling: Automatically infers union types for mixed-type arrays.
- Quoted Identifiers: Keys with dashes or spaces are quoted safely (e.g. 'content-type').
- Zero payload data is uploaded to Draftsbook servers or third parties.
- All type inference algorithms execute strictly within client-side memory.