JSON to TypeScript
Convert JSON samples into TypeScript interfaces entirely in your browser. No uploads, no accounts, privacy-first.
export interface Root {
id: number;
name: string;
email: string;
active: boolean;
roles: string[];
profile: Profile;
projects: Project[];
}
export interface Profile {
timezone: string;
avatarUrl: null;
}
export interface Project {
id: number;
title: string;
stars?: number;
archived?: boolean;
}
How it works
This converter walks a JSON document recursively and synthesizes TypeScript interfaces from the observed shape. Objects become named interfaces, arrays become typed lists, and primitive values map to string, number, boolean, or null. Nested objects generate additional interfaces so nested data stays readable. Because inference is driven only by the sample you paste, optional fields and unions are approximated from what is present—not from a schema registry. All parsing and code generation run with the browser’s JSON.parse and pure TypeScript string building. Nothing is posted to a server, stored in a database, or logged remotely. That makes the tool safe for sensitive API payloads, internal configs, and customer data during prototyping. Re-run the conversion after editing your JSON to refresh types. Prefer representative samples that include nulls and nested arrays so the generated interfaces match production more closely. Pair the output with manual refinements such as readonly modifiers or branded types when your domain needs stronger guarantees.
Frequently asked questions
Does my JSON leave the browser?
No. Parsing and type generation happen locally with JavaScript. PrivateDevTools never uploads your payload.
Can it handle nested objects and arrays?
Yes. Nested objects become additional interfaces and arrays are typed from their element samples.
Will optional fields be detected?
Yes, for arrays of objects. Every item is merged into one interface, and keys missing from some items are marked optional with ?.
Is the output production-ready?
It is a solid starting point. Review names, tighten unions, and add documentation before shipping types.