About Us

There is not much to explain about JSONTS. It is a JSON to TypeScript converter, and its job is turning a JSON sample into TypeScript interfaces and types, handling nested objects, unions and optional fields. What follows is how it works, why it exists, and what it does with your data.

Why we built this

There is no shortage of developer tools online; what is scarce is one that respects your time. JSONTS is deliberately narrow — it turns a JSON sample into TypeScript interfaces and types, handling nested objects, unions and optional fields and stops there. A small, honest tool beats a sprawling page that buries the answer under advertising.

How the calculation works

The whole calculation is client-side JavaScript. What happens is this: it infers a type for every value in the sample, widens arrays whose elements differ into a union, and marks a field optional when it is absent from some objects in an array — so the generated types reflect the sample rather than a hand-written guess. Because the method is published here, any disagreement you find can be traced to a particular step instead of being blamed on a black box.

Privacy by default

This is a local tool by construction. The JSON sample you paste never leaves your device; there is no endpoint to receive it and no log to read it back from. Disconnecting from the internet after the page loads changes nothing about how it behaves.

Who this is for

• developers who need an answer between two builds.
• engineers verifying output before it is committed.
• anyone who values a tool that needs no account.

Keeping it free

JSONTS is free to use and supported by advertising. Adverts are kept off the working part of the page, and no advertiser receives anything you type. If a page ever becomes slow or intrusive, that is a bug worth reporting.

Get in touch

Spotted a mistake or missing a feature? The contact page takes it. The suggestions that get acted on usually come from people who actually use the JSON to TypeScript converter.