JSON to TypeScript Converter — free browser tool for developers

#webdev #productivity #tools #javascript

JSON to TypeScript Converter – because typing interfaces by hand is tedious

I built a small tool to save time: JSON to TypeScript Converter.

You paste JSON, and it gives you TypeScript interfaces with inferred types, optional properties (based on null values), and nested object support. That’s it. No fluff.

It handles arrays, unions (like string | null), and nested objects. If your JSON has null in a field, it marks that property as optional. Arrays with mixed types become union types. Pretty standard, but consistent.

Why another one? I tried a few existing tools and kept running into small issues — incorrect typing on empty arrays, no support for duplicate object shapes, or weird formatting. So I made one that just works the way I want.

It’s free to use for basic conversion. Paste, copy, done.

There’s also a Pro tier ($9/month) for people using it regularly. It adds:

Named interface output (instead of just Interface or Type)
Support for enums when values are predictable (e.g., status: "active" | "inactive")
Export all as a module
No ads

I don’t need to sell you on typing your data — if you’re here, you already know. This just removes the repetitive part.

The tool runs entirely in-browser. Your data never hits a server. Even the Pro features are unlocked via local subscription (using Stripe), so no account creation.

Feedback? Issues? GitHub repo is public — open an issue or PR. I’ll keep improving it as I use it myself.

Try it next time you’re staring at API docs or a JSON response:

👉 https://tool-json-to-typescript-converter.vercel.app

No login. No tracking. Just paste and get types.