Zod · Type Alias

z.infer

z.infer extracts a static TypeScript type from a Zod schema. Use z.infer<typeof schema> to create a reusable alias that reflects the schema, including its output type when transformations are present.

How it works

z.infer is a TypeScript utility type that extracts the static type represented by a Zod schema. Apply it with typeof to a schema value, then reuse the resulting alias for compile-time checks; for transformed schemas, it corresponds to the schema's output type.

Syntax

type Inferred = z.infer<typeof schema>;

Parameters

Name	Type	Description
`schema`	`typeof Schema`	The Zod schema value whose static TypeScript type should be extracted.

Returns

The static TypeScript type inferred from the supplied Zod schema; for transformed schemas, this is the output type.

Key points

It derives a compile-time TypeScript type from the schema definition.
Use the utility type to extract the schema's static type and reuse that alias throughout TypeScript code.
The utility is applied to a schema value with typeof, as in z.infer<typeof Player>.
For transformed schemas, z.infer<typeof schema> is equivalent to the schema's output type.

Example: Infer a TypeScript type from a schema

import { z } from "zod";

const Player = z.object({
  username: z.string(),
  xp: z.number(),
});

type Player = z.infer<typeof Player>;

const player: Player = { username: "billie", xp: 100 };
console.log(player);

The type alias is inferred from the object schema, so the variable must have a string username and numeric xp.

When to use it

Synchronize validation and types

Define a TypeScript type from an object schema without duplicating its fields.

Compile-time assignment checking

Type variables or function inputs according to a schema's declared structure.

Model transformed output

Represent the result of a schema that transforms parsed data.

Interview questions

QWhat does z.infer do, and why is typeof used?

z.infer<typeof Schema> derives a static TypeScript type from the schema value Schema. The schema is written first, and the alias stays synchronized with its declared structure.

Follow-up: How do you obtain the pre-transformation type? Use z.input<typeof Schema>; z.infer<typeof Schema> corresponds to the output type.

QWhat type does z.infer produce for an object schema?

For an object schema containing username: z.string() and xp: z.number(), z.infer<typeof Player> produces a type requiring a string username and numeric xp. Assignments are then checked by TypeScript at compile time.

Follow-up: What happens if a value has xp: "100"? It is rejected because the inferred property type is number, regardless of runtime parsing.

QHow does z.infer behave with transformed schemas?

A schema with a transform can have different input and output types. z.infer<typeof mySchema> is equivalent to z.output<typeof mySchema>, while z.input<typeof mySchema> describes the input.

Follow-up: For a string-to-length transform, what are the two types? The input is string, and the output is number.

z.input
z.output
z.object
z.string
z.number

Source: Basic usage | Zod. Checked 2026-10-15.