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404 Page permalink

A 404 page may be accessed very often. Server-rendering an error page for every visit increases the load of the Next.js server. This can result in increased costs and slow experiences.

To avoid the above pitfalls, Next.js provides a static 404 page by default without having to add any additional files.

Customizing The 404 Page permalink

To create a custom 404 page you can create a pages/404.js file. This file is statically generated at build time.

// pages/404.js
export default function Custom404() {
  return <h1>404 - Page Not Found</h1>
}

500 Page permalink

By default Next.js provides a 500 error page that matches the default 404 page’s style. This page is not statically optimized as it allows server-side errors to be reported. This is why 404 and 500 (other errors) are separated.

Customizing The Error Page permalink

500 errors are handled both client-side and server-side by the Error component. If you wish to override it, define the file pages/_error.js and add the following code:

function Error({ statusCode }) {
  return (
    <p>
      {statusCode
        ? `An error ${statusCode} occurred on server`
        : 'An error occurred on client'}
    </p>
  )
}

Error.getInitialProps = ({ res, err }) => {
  const statusCode = res ? res.statusCode : err ? err.statusCode : 404
  return { statusCode }
}

export default Error

pages/_error.js is only used in production. In development you’ll get an error with the call stack to know where the error originated from.

Reusing the built-in error page permalink

If you want to render the built-in error page you can by importing the Error component:

import Error from 'next/error'
import fetch from 'isomorphic-unfetch'

const Page = ({ errorCode, stars }) => {
  if (errorCode) {
    return <Error statusCode={errorCode} />
  }

  return <div>Next stars: {stars}</div>
}

Page.getInitialProps = async () => {
  const res = await fetch('https://api.github.com/repos/zeit/next.js')
  const errorCode = res.statusCode > 200 ? res.statusCode : false
  const json = await res.json()

  return { errorCode, stars: json.stargazers_count }
}

export default Page

The Error component also takes title as a property if you want to pass in a text message along with a statusCode.