JSON to TypeScript
Generate TypeScript interfaces from a JSON sample, with nested types inferred, in your browser.
No Data Collection
No database, no accounts. We literally can't see your images.
Blazing Fast
Native browser processing — no upload, no waiting.
100% Free
No limits, no watermarks, no hidden fees. Ever.
No Account Required
Sign in? Never. Just open the tool and use it.
Generate TypeScript Interfaces from JSON
Types from a real payload
When you start consuming a new API, the fastest way to get type safety is to take a real response and turn it into TypeScript interfaces. Doing it by hand is slow and error-prone, especially once objects nest a few levels deep.
Paste a JSON sample and this tool walks the structure to produce matching interfaces, naming nested objects after the keys that hold them so the output reads the way you would have written it.
Optionals, unions, and merged array shapes
Inference goes beyond the obvious. When an array holds objects, their shapes are merged into a single interface: a key missing from some elements becomes optional with a question mark, and a field that holds different types across elements becomes a union such as number | string.
Empty arrays become unknown[] rather than a wrong guess, and keys that are not valid identifiers are quoted so the generated code always compiles.
Readable, ready-to-paste output
Nested interfaces are emitted before the types that use them, and repeated names are disambiguated automatically, so you can paste the result into a .ts file without rearranging anything. You can also rename the root interface to match your domain.
The generator infers from the sample you give it, so the more representative your JSON, including optional and edge-case fields, the more accurate the resulting types.
Processed locally, never uploaded
The whole thing runs in your browser. Your JSON, which often contains real API data, is never uploaded to a server.
Generation is instant and continues to work offline once the page is loaded.
Frequently asked questions
How are nested objects handled?
Each nested object becomes its own interface, named after the key that contains it, and is referenced from the parent. Interfaces are ordered so dependencies appear first.
What about arrays of objects with different fields?
Their shapes are merged into one interface. Keys missing from some elements become optional, and fields with differing types become a union like number | string.
Can I rename the root type?
Yes. The root interface defaults to Root, and you can set any valid TypeScript identifier instead.
Is my JSON uploaded?
No. Type generation happens entirely in your browser and your data never leaves your device.