What is JSON to TypeScript Converter?
JSON to TypeScript is a developer tool that automatically generates TypeScript interfaces and type definitions from JSON data. Instead of manually writing type declarations for API responses, configuration objects, or database records, this tool analyzes your JSON structure and produces clean, properly typed interfaces. It handles nested objects by creating separate named interfaces, detects array element types for accurate typing, and supports all JSON primitives including strings, numbers, booleans, and null values.
How to Use This Tool
Enter a name for your root interface in the text field (defaults to "Root"). Paste your JSON data into the input area, then click "Convert" to generate TypeScript interfaces. The tool creates a separate exported interface for each nested object, using PascalCase naming derived from the property keys. Arrays are typed based on their element values, and union types are generated when array elements have mixed types. Copy the generated TypeScript code with one click, or press "Clear" to start fresh.
Common Use Cases
- Generating type definitions for REST API responses to enable type-safe data handling in front-end code
- Creating interfaces from sample JSON payloads during the early stages of API integration
- Producing type declarations for configuration files, feature flags, and settings objects
- Converting database query results or mock data into TypeScript types for testing and development
Why Use a Client-Side Type Generator?
JSON data from your APIs often contains real user information, internal field names, and business logic structures. Pasting this data into an online tool that processes it server-side exposes your data model and potentially sensitive values. This converter runs entirely in your browser with zero network requests. Your JSON input and generated TypeScript output never leave your device. This makes it safe for use with production API responses, proprietary data schemas, and any JSON containing confidential information.
Frequently Asked Questions
How does the tool handle nested JSON objects?
Each nested object in your JSON is extracted into its own named TypeScript interface. The interface name is derived from the property key using PascalCase conversion. For example, a property called "shipping_address" containing an object would generate a separate "ShippingAddress" interface, and the parent interface would reference it by that type name. This produces clean, modular type definitions that are easy to maintain and reuse.
What happens with arrays that contain mixed types?
When an array contains elements of different types, the tool generates a union type. For example, an array with both strings and numbers would be typed as (string | number)[]. If the array contains objects with different structures, each unique shape is analyzed separately. Empty arrays are typed as unknown[] since the element type cannot be inferred without sample data. You can manually refine these types after generation.
Can I customize the root interface name?
Yes. The text field above the input area lets you specify any name for the root interface. The name is automatically converted to PascalCase and sanitized to be a valid TypeScript identifier. For example, entering "api-response" produces an interface named "ApiResponse". If you leave the field empty or enter an invalid name, it defaults to "Root". Nested interfaces derive their names from their respective property keys regardless of the root name.