Validate Everything With Zod: Schemas for Forms and APIs

TypeScript types vanish at runtime, so they can't protect you from bad API responses or user input. Zod validates at runtime AND infers your static types from the same schema — one source of truth.

Define Once, Infer the Type

import { z } from "zod";

const User = z.object({
  name: z.string().min(2),
  email: z.string().email(),
  age: z.number().int().positive().optional(),
});

type User = z.infer<typeof User>; // no duplicate interface needed

Validate Safely

const result = User.safeParse(input);
if (!result.success) {
  return { errors: result.error.flatten().fieldErrors };
}
const user = result.data; // fully typed & validated

Validate Environment Variables at Boot

A favorite production trick: parse process.env through a Zod schema at startup, so a missing variable fails loudly on deploy instead of silently at 3am.