JSON to TypeScript Converter — free browser tool for developers

JSON to TypeScript Converter – Paste JSON, Get Interfaces

I built a small tool to save time when working with APIs: JSON to TypeScript Converter.

You paste JSON, and it gives you clean TypeScript interfaces—no setup, no install. It handles nested objects, arrays, optional fields (based on null values), and even generates union types when values vary.

It’s something I’ve used daily for the past few months while integrating third-party APIs or mocking responses. Instead of writing interfaces by hand, I drop in sample JSON and copy the output. Cuts down on typos and speeds up typing setup.

The tool runs entirely in-browser—your data never hits a server. That means it’s fast, private, and works offline once loaded.

There’s a free tier that covers basic use: single JSON input, interface generation, and basic formatting.

For heavier use, there’s a $9/month Pro tier that adds:

• Multi-file output (generate multiple interfaces at once)
• Export as .ts files
• Support for enums and literal types
• Priority processing

No credit card needed to try Pro—just a GitHub login to authenticate.

I’ve kept the UI minimal because I didn’t want another flashy tool with distractions. Just paste, convert, copy.

It’s not perfect—edge cases exist, especially with irregular or sparse JSON—but it handles most real-world payloads I’ve thrown at it.

If you’re tired of manually writing interface User { id: number; name: string | null; } after every API response, give it a try.

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

Open source? Not yet—but I’m considering it based on feedback.

Built with Svelte and TypeScript (fitting, right?). Let me know if you find it useful or run into issues.