Logo Learn By Doing Light Mode
Validate everything with Zod in NextJS, Angular, Qwik, ...
Validate everything with Zod in NextJS, Angular, Qwik, ...

Add validation to NextJS Server actions, Forms, Angular HttpClient ....


# Introduction

Zod is a TypeScript-first schema declaration and validation library that simplifies validations tasks with an elegant, developer-friendly API. Born from the need for strong static typing, Zod allows developers to define the shape and constraints of their data using TypeScript's powerful type system.
Unlike other validation libraries that often require runtime type reflection or additional decorators, Zod leverages TypeScript’s compile-time features to ensure that data conforms to specified schemas without sacrificing performance.
In the world of software development, ensuring data integrity and validation is crucial, especially when dealing with complex applications.

Example. Try it

Let me show you a simple example.
In the next snippet I use Zod to create a Schema and validate a string that should have a minimum of 3 characters and a maximum of 10.
You can use this approach to validate Forms, your HTTP response using fetch or Angular HttpClient, validate React Server actions and much more...
Some snippets can be opened in a playground. Play with them!
Click or of the editor to practice
This approach not only helps in catching errors early in the development cycle but also enhances code readability and maintainability.
Whether you're validating API responses, parsing client-side inputs, or structuring backend data processes, Zod provides a robust, efficient toolkit that seamlessly integrates into any TypeScript project.
By the end of this article, you’ll appreciate how Zod’s concise syntax and comprehensive features make it an indispensable tool for modern TypeScript applications, helping developers enforce data validation rules and build safer, more predictable software.

# Next.js & Zod

Next.js, a leading React framework, offers out-of-the-box features for server-side rendering, static site generation, API routes and more...
With the introduction of Next.js v. 13/14 , developers can leverage Zod to validate form data by using server actions or create custom route handlers (I mean endpoints and REST API) , ensuring that the data conforms to the expected schema before it's processed or sent to the backend.
This is particularly useful in scenarios like user registrations, settings changes, or any form-based interaction where data integrity is paramount.
Using Zod in Next.js can streamline client-side validations by defining a schema that automatically checks the type and format of incoming data. This method reduces the amount of boilerplate code and increases the reliability of the application by catching errors early in the submission process.
Here’s a quick example of how you might use Zod to validate a simple user login REST API created in a Next.js application:

# Qwik & Zod

Qwik , a "new" fullstack framework known for its resume-able applications optimized for edge deployment, also integrates well with Zod to provide form validations. In Qwik, forms are a critical part of creating interactive applications, especially when dealing with user-generated content.
Zod's integration allows Qwik developers to define schemas that validate data on server but can also validate form inputs on the client side before they ever hit the server, greatly improving the user experience by ensuring that only valid data is processed.
The use of Zod in Qwik helps in maintaining a clean and manageable codebase, as validation logic is centralized and decoupled from UI logic. This makes the application easier to maintain and test

# Zod in Angular

Angular , a robust framework for building dynamic web applications, includes a well-equipped HTTP client for making requests to servers.
By leveraging Zod, developers can validate these server responses directly within Angular services or components, ensuring that the data structures received match the expected schemas.
This approach is a proactive defense mechanism that prevents potential bugs and errors that could arise from mismatched or malformed data.


  • Type Safety: Zod enhances Angular's built-in type safety by validating the runtime data against predefined schemas, thereby ensuring that the data conforms to the specified types.
  • Error Handling: By catching data errors as soon as a response is received, developers can handle them gracefully, providing better user feedback and avoiding runtime errors that might be harder to debug.
  • Development Efficiency: Defining schemas for server responses makes the code more predictable and easier to understand. It reduces the need for manual checks scattered throughout the application.
Our friend, Luca del Puppo , created an amazing video about this topic:

More resources from Luca:

# Installation

More info about installation and the whole documentation is available on Zod Website .

# Fetch Data in Vanilla JS

Now let me show you and example where we validate an object provided by the JSON Placeholder Users API website.
I'm using fetch but you can also axios or any other strategies / libraries to fetch data.
The response is just an object with an User, some primitives and nested object.

# Object Validation

How can we use this Schema to validate this object?
I won't explain describe every instruction because it's self-explanatory. For more information, consult the ZOD documentation .
Anyway, as you can see, you can validate each property, object or arrays by defining some validation rules:
Click or of the editor to practice


If we remove the comment in line 20 (where we check the website property), we can see how the parse function of Zod generates an error:
npm run dev with inspect
The safeParse function would simply generates an object like this: {success: false } that you can use to know if validation are passed or not

# Quiz Time

Validate Fields

What is the right syntax to validate an email address?
  • checkbox
  • checkbox
  • checkbox
  • checkbox

# Array Validation

Of course we can also validate arrays.
First we load an array of users from JSON Placeholder Users API
We can then simply create a new Schema to validate the array:
  • the array should contains User objects only
  • the array must not be empty
  • it should have exactly 10 users
background handwritten
Read the full article!
Sign Up
It's completely free!
Don’t have an account yet?
Sign Up!

Did you like this content?

Your feedback is very important to us!