JSON to TypeScript

Auto-infer interfaces and types from sample JSON

Root name: Style: Add readonly All fields optional (?) export

JSON input

TypeScript output

Type inference

number / string / boolean → primitive types
null → null
Object → nested interface or type
Homogeneous array → T[]
Heterogeneous array → union (A | B)[]
Empty array → unknown[]

Tips

Choose interface when you need declaration merging or extension
Choose type alias for unions, mapped or conditional types
readonly for immutable API responses
Mark fields optional (?) when the API may omit them
Pipe into npx prettier if you need stricter formatting