▲Next.js

Custom App Component

Updated 2026-04-20

2 min read

Custom App Component in Next.js

Introduction

In this tutorial, we will explore the concept of a custom App component in Next.js. The App component is a special file that allows you to customize the behavior and appearance of your entire application. It's an essential part of Next.js for advanced use cases such as global state management, error handling, and custom routing.

What is the App Component?

The App component is a top-level component in Next.js applications. By default, every Next.js app has an App component located at pages/_app.js. This file is automatically created when you initialize a new Next.js project with create-next-app.

Default Behavior

By default, the App component looks like this:

// pages/_app.js
import { AppProps } from 'next/app'

function MyApp({ Component, pageProps }: AppProps) {
  return <Component {...pageProps} />
}

export default MyApp

In this default setup:

Component: The current page being rendered.
pageProps: The initial props passed to the page component.

Customizing the App Component

You can customize the App component to add global styles, wrap your application with providers (like Redux or Context API), and handle custom error handling. Let's explore how to do this step-by-step.

Adding Global Styles

To add global styles, you can import them in the _app.js file:

// pages/_app.js
import '../styles/globals.css'
import { AppProps } from 'next/app'

function MyApp({ Component, pageProps }: AppProps) {
  return <Component {...pageProps} />
}

export default MyApp

Wrapping with Providers

If you're using a state management library like Redux or Context API, you can wrap your application in the provider component:

// pages/_app.js
import { Provider } from 'react-redux'
import store from '../store'
import '../styles/globals.css'
import { AppProps } from 'next/app'

function MyApp({ Component, pageProps }: AppProps) {
  return (
    <Provider store={store}>
      <Component {...pageProps} />
    </Provider>
  )
}

export default MyApp

Custom Error Handling

Next.js provides a built-in error boundary that catches errors in your application. You can customize this behavior by overriding the componentDidCatch method:

// pages/_app.js
import { AppProps } from 'next/app'
import '../styles/globals.css'

class MyApp extends App {
  componentDidCatch(error, errorInfo) {
    // Log the error to an error reporting service
    console.error('Caught an error', error, errorInfo)
  }

  render() {
    const { Component, pageProps } = this.props

    return <Component {...pageProps} />
  }
}

export default MyApp

Customizing the Document

The Document component is another special file in Next.js that allows you to customize the <html> and <body> tags. It's located at pages/_document.js. You can extend this component to add custom head elements or scripts:

// pages/_document.js
import { Html, Head, Main, NextScript } from 'next/document'

export default function Document() {
  return (
    <Html>
      <Head>
        <link rel="icon" href="/favicon.ico" />
        <meta name="description" content="Generated by create next app" />
        <meta charSet="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
      </Head>
      <body className="bg-gray-100">
        <Main />
        <NextScript />
      </body>
    </Html>
  )
}

Best Practices

Keep It Lightweight: The App component should remain lightweight to avoid unnecessary overhead.
Use Providers Wisely: Only wrap your application with necessary providers to prevent performance issues.
Error Handling: Implement robust error handling to provide a better user experience and easier debugging.
Document Customization: Use the _document.js file judiciously, as it can affect SEO and performance.

Conclusion

The App component in Next.js is a powerful tool for customizing your application's behavior and appearance. By understanding how to use it effectively, you can build more robust and maintainable applications. Remember to follow best practices to ensure optimal performance and user experience.

Feel free to experiment with the App component and customize it according to your project's needs. Happy coding!