JSON to TypeScript Converter

What does JSON to TypeScript conversion do?

Given a JSON sample — typically an API response — this tool infers TypeScript interfaces that describe its shape: nested objects become their own named interfaces, arrays are typed by their element type, and primitives map to string, number, boolean, or null. Instead of hand-writing types while squinting at a payload, you paste the payload and get the types.

Inference runs locally in your browser, so it's safe to paste responses from internal or authenticated APIs.

When to use it

The most common moment: you've just integrated a third-party API that has no official TypeScript SDK. Grab a real response from the docs or your Network tab, convert it, and drop the interfaces into your codebase — then tighten them by hand where you know more than the sample shows (union types, optional fields, enums).

It's also useful for typing configuration files, seeding types for a legacy JavaScript module you're migrating, or checking your mental model of a payload: if the generated interface surprises you, the data doesn't look like you thought it did.

Example and limitations

Converting {"id": 42, "tags": ["a"], "owner": {"name": "Ada"}} with root name ApiItem produces an ApiItem interface plus a nested Owner interface, with tags typed as string[]. Remember that inference only sees your sample: a field that happens to be null in the sample types as null, and a field absent from the sample won't appear at all. Convert a representative payload, then review — generated types are a starting point, not a contract.