JSON to TypeScript interface generator

How the shape becomes types

Typing an API response by hand is tedious and easy to get subtly wrong. This generator does the mechanical part: it walks a sample document and emits matching interfaces — an object becomes a named interface, a nested object becomes its own interface named after its key, and an array becomes a typed array (User[]). When an array holds several objects, it merges them, so a key that's present in some and absent in others is correctly marked optional with ?, and values with more than one type become a union like string | number.

Why the output is a starting point, not the final word

The important caveat with any sample-based generator: it can only describe the data it's shown. If a field is nullable but happens to be non-null in your sample, the inferred type won't know it's optional. If an enum-like string only ever shows one value here, you'll get string, not the literal union you might want. And an empty array can't reveal its element type, so it falls back to any[]. Treat the result as a fast, accurate scaffold of the shape you pasted — then tighten the types your API contract actually guarantees.

TypeScript or Go

This emits TypeScript interfaces, which lean on the language's structural typing, optional members and union types. If you're working in Go instead, the JSON to Go generator produces structs with the right field tags, and the JSON formatter is handy for confirming your sample is valid before you generate from it.