~/frontend-tools/json-to-typescript-converter
JSON to TypeScript Converter
Paste JSON and get TypeScript types for it. Nested objects become their own named interfaces, arrays get element types, fields missing from some array items become optional, and mixed values become unions, so the types match your real data.
Using the JSON to TypeScript Converter
How types are inferred
Strings, numbers and booleans map to string, number and boolean. Each nested object becomes a separate interface named after its key in PascalCase, such as Customer, which keeps the output readable and reusable.
Arrays and optional fields
For an array of objects, every item is inspected. A field present in some items and missing in others is marked optional with ?, which is exactly the kind of detail that is easy to miss by hand. Arrays of mixed primitives become union arrays like (string | number)[].
Null and empty values
A null value cannot tell you its real type, so it becomes null and is worth reviewing; in practice it is often string | null. Empty arrays become unknown[] for the same reason.
Interface or type
Interfaces can be extended and merged; type aliases can express unions and mapped types. For plain data shapes either works. Pick whichever your codebase already uses.
Validating real data
Types describe what your code expects, but they are erased when the code runs, so an API that returns something unexpected will still break things. Treat these generated types as a starting point, test them against several real responses, and add runtime validation at the boundaries where data enters your app.
Frequently asked questions
Does it detect dates?
No. Dates in JSON are strings, so they are typed as string. Convert them to Date objects in your code if needed.
Can it generate Zod schemas?
Not yet; the output is plain TypeScript types.
Is my JSON uploaded?
No, it is processed in your browser.