🔨 JSON to TypeScript Converter

What is JSON to TypeScript Conversion?

JSON to TypeScript conversion is the process of analyzing a JSON data structure and generating corresponding TypeScript interfaces or type aliases that describe the shape of that data. TypeScript is a statically typed superset of JavaScript that adds type annotations, enabling better tooling, autocompletion, and compile-time error detection. When working with API responses, configuration files, or any external JSON data, having accurate TypeScript types ensures that your code correctly handles the data structure and catches mismatches before runtime.

Manually writing TypeScript interfaces for complex JSON structures is tedious and error-prone. A single API response might contain deeply nested objects, arrays of mixed types, optional fields, and null values. This converter automates the entire process by recursively walking the JSON structure, detecting types for each field, creating named interfaces for nested objects, and handling edge cases like arrays containing objects with varying keys. The result is clean, production-ready TypeScript code that you can paste directly into your project.

How to Use This Tool

1. Paste your JSON data into the input panel on the left, or click "Load Sample" to try the tool with example data.
2. Configure the settings: set a root interface name, choose between interface and type style, toggle optional properties, and select your preferred indentation size.
3. The TypeScript output updates automatically as you type. You can also click "Convert" to trigger the conversion manually.
4. Click "Copy TypeScript" to copy the generated code to your clipboard, ready to paste into your project.
5. Use "Format JSON" to beautify your input JSON if it is minified or poorly formatted.

Key Features

• Recursive Object Handling - Nested objects automatically generate their own named interfaces using PascalCase names derived from the JSON keys.
• Smart Array Detection - Arrays of primitives become typed arrays (string[], number[]). Arrays of objects merge all element keys into a single unified interface. Mixed-type arrays produce union types.
• Interface or Type Style - Choose between TypeScript interface declarations and type alias declarations depending on your project conventions.
• Configurable Output - Customize the root name, toggle export keywords, mark all properties as optional, and choose your indent size.
• Syntax Highlighting - The output panel displays color-coded TypeScript with highlighted keywords, types, and property names for easy reading.
• Auto-Convert with Debounce - The tool converts automatically as you edit the JSON input, with a short debounce delay to keep things responsive.

Frequently Asked Questions

What is the difference between interface and type in TypeScript?

Both interface and type can describe object shapes in TypeScript. Interfaces support declaration merging and can be extended with the extends keyword, making them ideal for defining object contracts that might be augmented later. Type aliases are more flexible and can represent unions, intersections, tuples, and primitive types. For most object definitions, the choice comes down to project convention and personal preference.

How does the tool handle null values?

When a JSON field has a null value, the converter types it as null. If you know the field should be a specific type, you can edit the generated TypeScript to add the expected type as a union, for example: fieldName: string | null. The tool provides a starting point that accurately reflects the data it receives.

Can it handle arrays with mixed types?

Yes. When an array contains elements of different types, the converter creates a union type. For example, an array containing strings and numbers becomes (string | number)[]. Arrays containing a mix of objects and primitives will also produce accurate union types reflecting all the element types found in the data.

Does the tool detect date strings?

The converter checks string values against common ISO 8601 date patterns. When a date string is detected, the field is typed as string with an inline comment noting that it appears to be a date. This helps you decide whether to use a Date type or a custom date string type in your project.

Is my data safe when using this tool?

Absolutely. All conversion happens entirely in your browser using client-side JavaScript. Your JSON data is never sent to any server, stored, or logged. The tool works offline after the page loads, so you can safely convert sensitive API responses, configuration files, and proprietary data structures.