SYS.TOOLS
Free JSON to TypeScript converter: paste JSON and instantly get TypeScript interfaces. Handles nested objects, arrays, and primitives, all locally in your browser.
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Paste a JSON object and the converter walks it recursively, turning every object into a named TypeScript interface and inferring types for arrays and primitives. It runs entirely in your browser, so nothing gets uploaded.
I built this for anyone wiring up an API response and tired of hand-typing interfaces. Frontend and backend devs get correct types from one paste, then rename the root interface to match their own domain.
The tool parses your JSON and recursively generates TypeScript interfaces. Objects become interfaces, arrays infer their element type, and primitives map to string, number, boolean, or null.
Yes. Nested objects generate separate named interfaces (named after their key), and arrays infer the type from the first element.
Yes, 100% client-side. Your JSON never leaves your browser. There is no API call. The conversion happens instantly as you type.
Absolutely. Click the copy button and paste the interfaces directly into your TypeScript project. You may want to rename the root interface to match your domain.
