🧠 What Is TypeScript in Next.js? A Beginner’s Guide

If you’ve been building web apps with React or Next.js, chances are you’ve come across something called TypeScript. You might be wondering, “Do I really need it?” or “How does it even work with Next.js?”

This post breaks it all down—what TypeScript is, why it matters, and how it integrates beautifully with Next.js.

🔍 What is TypeScript?

TypeScript is a typed superset of JavaScript developed by Microsoft. That means it builds on top of JavaScript by adding static type checking.

Here’s a super simple example:

let name: string = "Next.js";
// TypeScript will catch this error:
name = 123; // ❌ Error: Type 'number' is not assignable to type 'string'

In JavaScript, that wouldn’t throw an error until runtime. But TypeScript catches it at development time—helping you avoid bugs before they happen.

🚀 Why Use TypeScript with Next.js?

Next.js is already a modern React framework, so adding TypeScript gives you superpowers:

✅ Error-catching at compile time
✅ Autocomplete and IntelliSense
✅ Self-documenting code
✅ Better collaboration in teams
✅ Confidence during refactoring

And the best part? Next.js has first-class TypeScript support built in. It just works.

⚙️ How to Add TypeScript to a Next.js Project

Already have a Next.js project in JavaScript?

You can convert it in seconds.

1. Install TypeScript and types:

npm install --save-dev typescript @types/react @types/node

2. Create a `tsconfig.json` file:

Just run:

npx tsc --init

Or, if you’re using Next.js, you can just rename a page (like index.js → index.tsx) and Next.js will auto-generate the tsconfig.json for you.

📂 File Naming in Next.js + TypeScript

File Type	Extension
Page Components	`.tsx`
Logic-only files	`.ts`
API Routes	`.ts`
Types/Interfaces	`.ts`

Use .tsx for files that include JSX. Otherwise, .ts is fine.

✍️ Declaring Types and Interfaces

Types help define how your data should look.

Example: Props in a Component

type ButtonProps = {
  label: string;
  onClick: () => void;
};

const Button = ({ label, onClick }: ButtonProps) => (
  <button onClick={onClick}>{label}</button>
);

This ensures the label is a string, and onClick is a function.

🧱 Real Example in Next.js

Let’s look at a full functional component in a Next.js + TypeScript app:

// pages/index.tsx

import type { NextPage } from 'next';

const Home: NextPage = () => {
  return (
    <div>
      <h1>Hello from TypeScript!</h1>
    </div>
  );
};

export default Home;

The NextPage type helps with better typing and autocomplete in Next.js pages.

🧰 Helpful TypeScript Tools in Next.js

getStaticProps, getServerSideProps, getInitialProps all support typed return types
You can strongly type your API routes using NextApiRequest and NextApiResponse
Use interface or type to create reusable types across components

🤔 Should You Use TypeScript in Your Next.js App?

If you:

Want better tooling
Care about clean, readable code
Are building anything more than a simple landing page

Then yes, TypeScript is 100% worth it.

It might feel verbose at first, but once you’re used to it, you’ll wonder how you ever lived without it.

✅ Final Thoughts

TypeScript + Next.js = a powerful combo for building scalable, maintainable, and bug-resistant React applications. It’s beginner-friendly and future-proof.

If you’re just getting started, you don’t need to go full TypeScript all at once. Migrate gradually, or start with new files.

💡 Want More?

Let me know if you’d like a follow-up post on:

Converting an entire JS Next.js project to TS
Creating a global types folder
Using TypeScript with Zustand or Supabase

Happy coding! ✨