Why Z.infer is use in Zod ?

 Without z.infer, you must manually create the TypeScript type.

Without z.infer

import { z } from "zod";

const UserSchema = z.object({
  name: z.string(),
  age: z.number(),
});

type User = {
  name: string;
  age: number;
};

Notice that you're writing the same structure twice:

1. Zod schema (for validation)
2. TypeScript type (for type checking)

---

With z.infer

import { z } from "zod";

const UserSchema = z.object({
  name: z.string(),
  age: z.number(),
});

type User = z.infer<typeof UserSchema>;

Now you only write the structure once (in the schema), and TypeScript generates the type for you.

The problem without z.infer

Suppose you add an email field:

const UserSchema = z.object({
  name: z.string(),
  age: z.number(),
  email: z.string(),
});

You must also remember to update:

type User = {
  name: string;
  age: number;
  email: string;
};

If you forget, your schema and type become inconsistent.

So, without z.infer = manual type creation.
With z.infer = automatic type creation from the schema.