Does this handle nested objects?

Yes. Each nested object becomes a separate named interface. The names are derived by PascalCasing the parent property name.

How are arrays typed?

For uniform arrays (all elements the same primitive type) the output is e.g. string[]. For arrays of objects, a separate interface is generated. If array elements have different keys, missing keys are marked optional with ?.

What happens with null values?

A null value produces a type union like string | null, preserving the base type inference from other array elements or defaulting to null if that is the only value.

Does this support JSON arrays at the root?

Yes. If the root JSON is an array, the tool infers the element type and produces a Root type alias of the form type Root = ElementType[].

Are the generated types safe to use directly?

They are a best-effort inference based on the sample JSON you paste. If your API can return additional shapes not present in the sample, you should review and adjust the generated types accordingly.

JSON to TypeScript

Developer Tools· 33 tools

Free JSON to TypeScript interface generator. Paste any valid JSON object and get fully typed TypeScript interfaces with correct primitive types, nested object interfaces, array types, null unions, and optional keys inferred from mixed array elements. Root interface name is configurable. The generator is deterministic and runs entirely in your browser — no data is sent to a server.

Root interface name

Input JSON

TypeScript Output

Frequently Asked Questions

References

TypeScript Handbook — Object Types — TypeScript
JSON specification — ECMA-404 — Ecma International

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Frequently Asked Questions

References and sources

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