What is Zod?

Zod is a schemaA schema is a structured representation or blueprint that defines the organization, structure, and constraints of data within a database or any other data storage system declaration and validation library for typescript. It allows us to design schemas for any data, including primitive data types, objects, arrays, and more.

Why do we need Zod?

Zod provides runtime schema validation for typescript. Schema validation confirms that data adheres to a standard defined by the developer. It is advantageous when getting user data in forms, sending data to APIs, and more. Typically, typescript provides schema validation at the compile time only, whereas Zod provides validation at runtime.

Zod in code

To start with Zod, ensure node and npm are installed on your machine. We can use npm to install Zod using the command given below:

npm install zod

Now, we’ll define a very simple schema validator. First, we import zod in our file. Next, we define a simple string schema that accepts a string of minimum length 5 and maximum length 10. Now, if we parse a string of length 9, it will be parsed successfully and returned. Run the code below to see the output:

import { z } from "zod"
const userInput = z.string().min(5).max(10);
console.log(userInput.parse("Hello Zod"));

However, if the length of the string is more than 10 or less than 5, an error will be thrown. In the code given below, the length of the string is 24. Run the code to see the output.

import { z } from "zod"
const userInput = z.string().min(5).max(10);
console.log(userInput.parse("Hello Zod and Typescript"));

The output of the code snippet above throws a ZodError. This error interrupts the runtime, which is undesirable in client-server web applications. However, we can avoid this error in Zod as discussed in the next section.

How to avoid errors?

To avoid errors when parsing fails, we can use the safeParse function. It returns status 400 and an object with the success property set to true if the string is parsed successfully, otherwise, it’s set to false. In the latter case, the function also returns an error property containing the error object.

In the code given below, we will use the safeParse function. Run the code to see the output.

import { z } from "zod"
const userInput = z.string().min(5).max(10);
const result = userInput.safeParse("Hello Zod and Typescript");
if (result.success) {
  console.log('Valid Data', result.data);
} else {
  console.error('Invalid Data', result.error.message);
}

The code will print Valid Data along the data if the string is parsed successfully, otherwise it will print Invalid Data along with the message in the error.

Validating and parsing objects

Similarly, we can use Zod to validate a complex object. 

import { z } from 'zod'
import { ZodTypeAny } from 'zod';
const FormData = z.object({
  username: z.string().min(1).max(18),
  email: z.string().email(),
});
const validUserData = { username: 'Alice', email: 'alice@gmail.com' };
const invalidUserData = { username: 'Bob', email: 'bobmail.com' }; 
const validateFormData = (data: any, schema: ZodTypeAny) => {
  const result = schema.safeParse(data);
  if (result.success){
  console.log('Valid Data', result.data);
} else {
  console.error('Invalid Data', result.error.message);
}
};
console.log('Parsing valid user data');
validateFormData(validUserData, FormData);
console.log('Parsing invalid user data');
validateFormData(invalidUserData, FormData);

The code implements the following steps:

  • Lines 4–7: We define an object called FormData that contains two variables, username and email. This object defines our schema for a user.

  • Lines 9–10: We define sample data in variables validUserData and invalidUserData. Note the email in invalidUserData is bobmail.com which is an invalid format.

  • Lines 12–19: We define a validateFormData function. In this function, we have set the schema type to ZodTypeAny so that it accepts any type of structure or data without prior validation. In the function, the result variable stores the object returned by safeParse function. If the data is parsed successfully, it prints Valid Data along with data object. Otherwise, it prints the error message.

  • Lines 22–25: We call the validateFormData function to validate validUserData and invalidUserData against FormData.

Conclusion

Summing it up, Zod is a great way to ensure data validity and integrity in typescript applications. In this answer, we have discussed basic functions to parse and validate data. However, Zod offers a variety of functions to customize validation functions, transform data during validation, asynchronous validation, and more.

Free Resources

Copyright ©2025 Educative, Inc. All rights reserved