As your React projects grow, organizing validation logic becomes essential for maintainability and scalability. A clear structure for Zod schemas helps you avoid duplication, promote reuse, and make it easier for your team to collaborate. Typically, you should keep Zod schemas out of your component files and place them in dedicated directories, such as a validation or schemas folder at the root or within feature modules. This separation allows you to import and update validation logic without cluttering your UI code.

When multiple forms share similar validation rules—like email addresses or user profiles—it is best practice to define reusable schema fragments. For example, you might create a fields.ts file containing common Zod definitions, such as emailSchema or passwordSchema. These fragments can then be composed into larger schemas using Zod's .merge() or .extend() methods, making your code DRY (Don't Repeat Yourself) and consistent across the application.

Sharing and reusing validation logic is often achieved by exporting these schema fragments or utility functions. You might group related schemas by feature (such as userSchemas.ts for all user-related forms) or by domain (like authSchemas.ts for authentication). This approach enables you to update validation rules in a single place and apply them across multiple forms, reducing the chance of inconsistencies or errors.

For example, you could define a reusable email schema in a shared file:

// fields.ts
import { z } from "zod";

export const emailSchema = z.string().email("Invalid email address");

Then, use it in different form schemas:

// userSchemas.ts
import { z } from "zod";
import { emailSchema } from "./fields";

export const registerSchema = z.object({
  email: emailSchema,
  password: z.string().min(8, "Password must be at least 8 characters"),
});

export const loginSchema = z.object({
  email: emailSchema,
  password: z.string(),
});

This pattern allows you to maintain a single source of truth for shared validation logic, making updates straightforward and reducing code duplication.