JSON to TypeScript Interfaces

Paste a JSON blob and get TypeScript interface declarations. Handles nested objects, arrays, and union types. Runs in your browser.

Runs 100% in your browser — nothing is uploaded.

JSON input

Root interface name

TypeScript (3 interfaces)

interface Root {
  user: User;
}

interface User {
  id: number;
  name: string;
  email: string;
  active: boolean;
  roles: string[];
  profile: Profile;
}

interface Profile {
  avatar: string;
  joinedAt: string;
}

Frequently asked

How does it handle arrays of mixed types?

It creates a union: Array<string | number> for a mixed array. If all elements share the same shape, you get T[] for that T.

What about optional fields?

The tool assumes every field is required based on the example JSON. If your real data sometimes omits fields, mark them optional (?:) manually — one common enhancement to add later.

Nested interface names?

Named after the JSON key in PascalCase. "user.profile" becomes interface Profile. Duplicate names re-use the same interface.

Frequently asked

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