You can “brand” your types so that TypeScript sees them as unique, even if they’re plain strings or numbers at runtime.

import { z } from 'zod';

const emailSchema = z.string().email().brand<'EmailAddress'>();

type EmailAddress = z.infer<typeof emailSchema>;
// => string & { __brand: "EmailAddress" }

const email = emailSchema.parse('test@example.com');
// Type is EmailAddress

function sendEmail(to: EmailAddress) {
  console.log('Sending email to', to);
}

sendEmail(email);
// Works

sendEmail('unbranded string');
// Type error: not EmailAddress

Zod v4

In Zod v4, z.string().email() is preferably written as z.email(). The .brand() method also accepts an optional second argument ("in", "out", or "inout") to control where the brand appears in the inferred type.

Branding is purely a TypeScript compile-time trick, but it helps you avoid passing, for example, a plain string where an EmailAddress is required. You can brand objects, too.

Steve Kinney

Type Branding with Zod