Programming Language Tools

JSON to TypeScript

Generate a TypeScript interface from JSON, inferring property types automatically.

Paste JSON below - this tool infers property types and generates a matching TypeScript interface, with nested interfaces for nested objects.

JSON Root Interface Name

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Type inference from a single JSON sample is a best guess - review the generated types, especially for fields that could reasonably be optional or a union of types.

What Does This Tool Do?

It analyzes your JSON's structure and generates a TypeScript interface declaration with property types inferred from the actual values - strings, numbers, booleans, arrays, and nested objects (as their own nested interfaces).

Why Use This Tool?

Writing TypeScript interfaces by hand for a large API response is tedious and error-prone - this tool generates a solid starting point instantly from a real example response.

How to Use It

Paste a sample JSON object (ideally a realistic, representative example).
Click Convert.
Copy the generated interface(s) into your TypeScript project.

Limitations

Type inference from one JSON sample is necessarily a best guess - a field that's sometimes null, sometimes a number, won't be perfectly captured from a single example. Review and adjust the generated types (especially optional fields marked with ?) for your actual data's full range.

Frequently Asked Questions

From the values in your sample JSON: strings, numbers, booleans, arrays and nested objects each become the matching TypeScript type, with nested objects turned into their own interfaces.

A single sample cannot show that, so check the result and mark such fields as optional (field?: type) or add | null yourself.

No. Interfaces only exist at compile time. Use a runtime validator such as Zod if you need to check API responses.