JSON → TypeScript
Generate TypeScript interfaces or Zod schemas from any JSON, automatically and client-side.
TypeScript interfaces vs Zod schemas
TypeScript interfaces exist only at compile time: they validate types during development and are erased at runtime. Zod schemas are runtime objects that can parse and validate data, generate TypeScript types via z.infer<>, and throw detailed errors when data doesn't match.
Use interfaces when you control the data source and just need IDE support. Use Zod (or similar: Valibot, Yup, ArkType) when you receive data from untrusted sources like APIs, form inputs, or config files.
How type inference works
This tool traverses your JSON value recursively. Arrays are typed by their elements: if all elements share the same structure, a single type is inferred; mixed arrays produce union types (string | number). Missing keys across objects are marked optional.
Next steps after generation
The generated types are a starting point. For stricter validation, refine Zod schemas with constraints like z.string().email(), z.number().positive(), or z.array(...).min(1).
For TypeScript interfaces, consider adding readonly modifiers and replacing any with proper union types. If your JSON comes from an API with a published OpenAPI spec, tools like openapi-typescript or Orval can generate more complete, versioned types directly from the spec.