What JSON structures are supported?

Supports objects, arrays, nested objects, and basic types (string/number/boolean/null). Types are automatically inferred.

Can the generated interfaces be used directly?

Yes. The generated TypeScript interface code follows standard syntax. Copy and paste directly into a .ts file.

How are null values handled?

Null values are marked as union types like string | null.

Is my data uploaded to a server?

No. All type inference and code generation is done locally in your browser.

Does it support array type inference?

Yes. Arrays are inferred as Type[] based on element types. Mixed-type arrays become union type arrays.

Free JSON to TypeScript Interface

Automatically convert JSON data to TypeScript interface/type definitions, supporting nested objects and arrays

What Can the JSON to TypeScript Interface Tool Do?

The JSON to TypeScript Interface tool is a free online developer tool that automatically converts JSON data into TypeScript interface or type definitions. It supports nested objects, arrays, and basic type inference, automatically generating multiple interface definitions. Options like export and readonly can be configured. Suitable for API response type definitions, data model generation, and TypeScript project initialization. All processing is done locally in your browser.

Core Features

Auto Type Inference: string/number/boolean/null automatically identified
Nested Objects: Automatically split into separate interface definitions
Array Types: Infer element types, support union type arrays
Configurable: export/readonly/root interface name adjustable
Complete Code: Generate ready-to-use TypeScript code

How to Use

1. Paste JSON data in the input box.

2. Adjust options (interface name, export, readonly).

3. Click "Generate Interface" to see TypeScript code.

4. Click "Copy Code" or "Download TS" to get the result.

Use Cases

Case 1: API Type Definitions

Automatically convert API response JSON to TypeScript interfaces for quick type safety.

Case 2: Data Models

Generate TypeScript type definitions from JSON configuration or data samples.

Case 3: Project Migration

Convert JavaScript project JSON data to TypeScript interfaces, accelerating typed migration.

Technical Background

TypeScript interfaces define the shape of objects, providing compile-time type checking. When inferring types from JSON, null values generate union types (e.g., string | null), arrays are inferred based on elements (e.g., number[]), and nested objects are automatically split into separate interfaces. The difference between type and interface: interfaces support declaration merging, while types support union/intersection types. In real projects, consider combining with JSDoc for property documentation, and using tools like json-schema-to-typescript for more complex scenarios.

🔷 JSON to TypeScript Interface

📥 JSON Input

📋 TypeScript Interface