JSON to TypeScript

No. Parsing and type generation run entirely in your browser using the built-in JSON parser. Nothing you paste is sent to a server, so it is safe to use with private or production data.

Each nested object becomes its own named interface, referenced by name from the parent. Arrays of objects are merged into a single element interface, and keys missing from some elements are marked optional with a ?. Arrays of primitives become a typed array such as string[], and empty arrays become unknown[].

Interface mode emits TypeScript interface declarations; type mode emits type aliases (type X = { … }). Both describe the same shape — pick whichever your codebase prefers. You can also choose 2-space, 4-space, or tab indentation and name the root type.

A field that is null in one sample and a value in another becomes a union with null kept last, like string | null. An array mixing several primitive types becomes a parenthesised union such as (string | number)[]. Because JSON has no integer type, every number is typed as number.