Security & Quality

Zod Input Validation

Define and validate data schemas with Zod for type-safe input validation in TypeScript applications.

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Overview

Zod is a TypeScript-first schema validation library that lets you define schemas and automatically infer TypeScript types from them. It eliminates the need to write types and validation logic separately, providing a single source of truth for data shapes. Zod schemas are composable, allowing you to build complex validations from simple building blocks.

The library supports all JavaScript primitives plus complex types like objects, arrays, unions, intersections, tuples, records, maps, and sets. It provides built-in validators for common patterns like email, URL, UUID, CUID, regex, and numeric ranges. Transform functions allow you to coerce and modify data during parsing, while refinements let you add custom validation logic.

Zod integrates with popular frameworks and libraries including React Hook Form, tRPC, Astro, Next.js, and Hono. For API input validation, Zod schemas can validate request bodies, query parameters, and path parameters, returning detailed error messages with the exact path to invalid fields. The `.safeParse()` method provides non-throwing validation, returning a discriminated union of success or error results.

Who Is This For?

Validate API request bodies with detailed error messages
Define form schemas with React Hook Form integration
Parse and transform environment variables at startup
Create reusable validation schemas for shared data models

Installation

Setup for Claude Code

npm install zod

Configuration

import { z } from "zod"

const UserSchema = z.object({
  name: z.string().min(2).max(100),
  email: z.string().email(),
  age: z.number().int().positive().optional(),
  role: z.enum(["admin", "user", "moderator"]),
})

type User = z.infer<typeof UserSchema>

const result = UserSchema.safeParse(requestBody)
if (!result.success) {
  return res.status(400).json({ errors: result.error.issues })
}