JSON to TypeScript Converter

JSON to TypeScript Converter is a free browser tool that turns a JSON sample into TypeScript interfaces or type aliases. You can set the root name, output style, indent and null handling, then use the Generate, Copy, Download .ts and Reset controls.

The page says it needs no account and has no usage cap. Conversion runs in the browser and nothing is sent to a server. Types are inferred from the one sample you paste in.