How are interfaces named?

Top-level is `Root`; nested objects use the PascalCase form of their parent key. Rename in your editor afterwards if you prefer.

Are optional fields detected?

A single JSON sample assumes every field is present. For union / optional inference across multiple samples, edit the result manually.

Only plain TypeScript interfaces today. If you need runtime validation, convert the result into a Zod schema as a separate step.

Example

{
  "id": 1,
  "name": "yutils",
  "active": true,
  "owner": { "email": "hello@yutils.dev", "verified": false }
}

interface Root {
  id: number;
  name: string;
  active: boolean;
  owner: Owner;
}

interface Owner {
  email: string;
  verified: boolean;
}

Nested objects become separate interfaces. Arrays are typed from their first element. Mixed nulls produce union types.

Usage / FAQ

Q.How are interfaces named?: A.Top-level is `Root`; nested objects use the PascalCase form of their parent key. Rename in your editor afterwards if you prefer.
Q.Are optional fields detected?: A.A single JSON sample assumes every field is present. For union / optional inference across multiple samples, edit the result manually.
Q.Can it produce Zod or io-ts schemas?: A.Only plain TypeScript interfaces today. If you need runtime validation, convert the result into a Zod schema as a separate step.

Fun facts

TypeScript was announced by Microsoft's Anders Hejlsberg in 2012 — the same person who built Turbo Pascal (1983), Delphi (1995), and C# (2000). Critics dubbed it 'C# for JavaScript,' but the genuine motivation was 'JavaScript doesn't scale to large codebases.'
Wikipedia — TypeScript history
TypeScript uses structural typing (duck typing) — compatibility is determined by shape (properties, methods), not by the class name like Java/C#'s nominal typing. That's why interfaces inferred from JSON map cleanly onto runtime objects.
TS Handbook
JSON → TypeScript inference falls down on never-seen cases. Is an empty array `[]` an `unknown[]`? `never[]`? `any[]`? Good generators use context (key names, sibling samples), but the deterministic answer ultimately needs human judgment.
TS — Everyday Types