The tool analyzes your JSON structure and infers TypeScript types from the data. It detects primitives (string, number, boolean), objects, arrays, and nullable values, then generates matching interface or type definitions.

Use interfaces for object shapes and classes. Use type aliases for unions, intersections, and primitive aliases. Interfaces can be extended and merged, while types are more flexible with complex types.

When enabled, all properties are marked with '?' making them optional. This is useful when not all fields are guaranteed to be present in every object instance.

Arrays are detected and typed based on their elements. Homogeneous arrays get a single type (string[], number[]), while mixed arrays get union types (string | number)[].

Yes, nested objects are automatically detected and can generate separate named interfaces. Enable 'Extract nested types' to create reusable type definitions for nested structures.

Null values are typed as 'null', and when combined with other values they create union types (e.g., 'string | null'). This ensures type safety with potentially missing data.

The tool examines the actual JSON values. Numbers (including integers and floats) become 'number', strings become 'string'. Numeric strings are typed as 'string'.

Readonly marks all properties as immutable (readonly fieldName: type). Use this for configuration objects, API responses, or any data that shouldn't be modified after creation.

Yes, the tool handles JSON of any size entirely in your browser. Complex nested structures are fully supported with proper indentation and formatting.

Copy the output and paste it into a .ts or .d.ts file in your project. The generated types work with TypeScript's type checking and provide autocomplete in your IDE.

JSON Input

TypeScript Output

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