JSON to TypeScript

A free online converter that takes any JSON object — from a raw API response, a config file, or a database row — and generates typed TypeScript interfaces and types for it. Paste JSON on the left, get ready-to-use type definitions on the right. When you're building a TypeScript app, hand-writing interfaces for large or unfamiliar payloads is tedious and error-prone. This tool reads the structure of your JSON and infers the shape: objects become interfaces, arrays get typed by their first element, nullables are marked optional, and deeply nested data produces properly named, hierarchical types. It handles common scenarios like union types (a field that can be string or number), arrays of mixed types, and optional properties inferred from missing keys. Typical workflow: copy a sample response from Postman or your browser's network tab, paste it in, and immediately get interfaces you can paste into a .ts file. Use the generated types with fetch wrappers, React props, Zod schemas, or API client generators. The tool also offers naming options — choose interface vs type alias, configure root type naming, and toggle between readonly and mutable properties. Everything runs client-side, so even proprietary or internal API shapes never leave your machine. It's a daily time-saver for frontend and full-stack developers working in typed codebases.