getStaticProps

Exporting a function called getStaticProps will pre-render a page at build time using the props returned from the function:

import type { InferGetStaticPropsType, GetStaticProps } from 'next'
 
type Repo = {
  name: string
  stargazers_count: number
}
 
export const getStaticProps = (async (context) => {
  const res = await fetch('https://api.github.com/repos/vercel/next.js')
  const repo = await res.json()
  return { props: { repo } }
}) satisfies GetStaticProps<{
  repo: Repo
}>
 
export default function Page({
  repo,
}: InferGetStaticPropsType<typeof getStaticProps>) {
  return repo.stargazers_count
}

You can import modules in top-level scope for use in getStaticProps. Imports used will not be bundled for the client-side. This means you can write server-side code directly in getStaticProps, including fetching data from your database.

Context parameter

The context parameter is an object containing the following keys:

getStaticProps return values

The getStaticProps function should return an object containing either props, redirect, or notFound followed by an optional revalidate property.

props

The props object is a key-value pair, where each value is received by the page component. It should be a serializable object so that any props passed, could be serialized with JSON.stringify.

export async function getStaticProps(context) {
  return {
    props: { message: `Next.js is awesome` }, // will be passed to the page component as props
  }
}

revalidate

The revalidate property is the amount in seconds after which a page re-generation can occur (defaults to false or no revalidation).

// This function gets called at build time on server-side.
// It may be called again, on a serverless function, if
// revalidation is enabled and a new request comes in
export async function getStaticProps() {
  const res = await fetch('https://.../posts')
  const posts = await res.json()
 
  return {
    props: {
      posts,
    },
    // Next.js will attempt to re-generate the page:
    // - When a request comes in
    // - At most once every 10 seconds
    revalidate: 10, // In seconds
  }
}

Learn more about Incremental Static Regeneration.

The cache status of a page leveraging ISR can be determined by reading the value of the x-nextjs-cache response header. The possible values are the following:

• MISS - the path is not in the cache (occurs at most once, on the first visit)
• STALE - the path is in the cache but exceeded the revalidate time so it will be updated in the background
• HIT - the path is in the cache and has not exceeded the revalidate time

notFound

The notFound boolean allows the page to return a 404 status and 404 Page. With notFound: true, the page will return a 404 even if there was a successfully generated page before. This is meant to support use cases like user-generated content getting removed by its author. Note, notFound follows the same revalidate behavior described here.

export async function getStaticProps(context) {
  const res = await fetch(`https://.../data`)
  const data = await res.json()
 
  if (!data) {
    return {
      notFound: true,
    }
  }
 
  return {
    props: { data }, // will be passed to the page component as props
  }
}

Good to know: notFound is not needed for fallback: false mode as only paths returned from getStaticPaths will be pre-rendered.

redirect

The redirect object allows redirecting to internal or external resources. It should match the shape of { destination: string, permanent: boolean }.

In some rare cases, you might need to assign a custom status code for older HTTP clients to properly redirect. In these cases, you can use the statusCode property instead of the permanent property, but not both. You can also set basePath: false similar to redirects in next.config.js.

export async function getStaticProps(context) {
  const res = await fetch(`https://...`)
  const data = await res.json()
 
  if (!data) {
    return {
      redirect: {
        destination: '/',
        permanent: false,
        // statusCode: 301
      },
    }
  }
 
  return {
    props: { data }, // will be passed to the page component as props
  }
}

If the redirects are known at build-time, they should be added in next.config.js instead.

Reading files: Use process.cwd()

Files can be read directly from the filesystem in getStaticProps.

In order to do so you have to get the full path to a file.

Since Next.js compiles your code into a separate directory you can't use __dirname as the path it returns will be different from the Pages Router.

Instead you can use process.cwd() which gives you the directory where Next.js is being executed.

import { promises as fs } from 'fs'
import path from 'path'
 
// posts will be populated at build time by getStaticProps()
function Blog({ posts }) {
  return (
    <ul>
      {posts.map((post) => (
        <li>
          <h3>{post.filename}</h3>
          <p>{post.content}</p>
        </li>
      ))}
    </ul>
  )
}
 
// This function gets called at build time on server-side.
// It won't be called on client-side, so you can even do
// direct database queries.
export async function getStaticProps() {
  const postsDirectory = path.join(process.cwd(), 'posts')
  const filenames = await fs.readdir(postsDirectory)
 
  const posts = filenames.map(async (filename) => {
    const filePath = path.join(postsDirectory, filename)
    const fileContents = await fs.readFile(filePath, 'utf8')
 
    // Generally you would parse/transform the contents
    // For example you can transform markdown to HTML here
 
    return {
      filename,
      content: fileContents,
    }
  })
  // By returning { props: { posts } }, the Blog component
  // will receive `posts` as a prop at build time
  return {
    props: {
      posts: await Promise.all(posts),
    },
  }
}
 
export default Blog

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