This guide will help you understand how to transition from an existing Gatsby project to Next.js. Migrating to Next.js will allow you to:
And more! Let’s walk through a series of steps to complete the migration.
package.json and dependenciesThe first step towards migrating to Next.js is to update package.json and dependencies. You should:
react and react-dom).next.scripts. One is next dev, which runs a development server at localhost:3000. You should also add next build and next start for creating and starting a production build.Here's an example package.json (view diff):
{
"scripts": {
"dev": "next dev",
"build": "next build",
"start": "next start"
},
"dependencies": {
"next": "latest",
"react": "latest",
"react-dom": "latest"
}
}
Gatsby uses the public directory for the compiled output, whereas Next.js uses it for static assets. Here are the steps for migration (view diff):
.cache/ and public from .gitignore and delete both directories.static directory as public..next to .gitignore.Both Gatsby and Next support a pages directory, which uses file-system based routing. Gatsby's directory is src/pages, which is also supported by Next.js.
Gatsby creates dynamic routes using the createPages API inside of gatsby-node.js. With Next, we can use Dynamic Routes inside of pages to achieve the same effect. Rather than having a template directory, you can use the React component inside your dynamic route file. For example:
createPages API inside gatsby-node.js for each blog post, then have a template file at src/templates/blog-post.js.pages/blog/[slug].js which contains the blog post template. The value of slug is accessible through a query parameter. For example, the route /blog/first-post would forward the query object { 'slug': 'first-post' } to pages/blog/[slug].js (learn more here).With Gatsby, global CSS imports are included in gatsby-browser.js. With Next, you should create a custom _app.js for global CSS. When migrating, you can copy over your CSS imports directly and update the relative file path, if necessary. Next.js has built-in CSS support.
The Gatsby Link and Next.js Link component have a slightly different API.
// Gatsby
import { Link } from 'gatsby'
export default function Home() {
return <Link to="/blog">blog</Link>
}
// Next.js
import Link from 'next/link'
export default function Home() {
return (
<Link href="/blog">
<a>blog</a>
</Link>
)
}
Update any import statements, switch to to href, and add an <a> tag as a child of the element.
The largest difference between Gatsby and Next.js is how data fetching is implemented. Gatsby is opinionated with GraphQL being the default strategy for retrieving data across your application. With Next.js, you get to choose which strategy you want (GraphQL is one supported option).
Gatsby uses the graphql tag to query data in the pages of your site. This may include local data, remote data, or information about your site configuration. Gatsby only allows the creation of static pages. With Next.js, you can choose on a per-page basis which data fetching strategy you want. For example, getServerSideProps allows you to do server-side rendering. If you wanted to generate a static page, you'd export getStaticProps / getStaticPaths inside the page, rather than using pageQuery. For example:
// src/pages/[slug].js
// Install remark and remark-html
import { remark } from 'remark'
import html from 'remark-html'
import { getPostBySlug, getAllPosts } from '../lib/blog'
export async function getStaticProps({ params }) {
const post = getPostBySlug(params.slug)
const markdown = await remark()
.use(html)
.process(post.content || '')
const content = markdown.toString()
return {
props: {
...post,
content,
},
}
}
export async function getStaticPaths() {
const posts = getAllPosts()
return {
paths: posts.map((post) => {
return {
params: {
slug: post.slug,
},
}
}),
fallback: false,
}
}
You'll commonly see Gatsby plugins used for reading the file system (gatsby-source-filesystem), handling markdown files (gatsby-transformer-remark), and so on. For example, the popular starter blog example has 15 Gatsby specific packages. Next takes a different approach. It includes common features directly inside the framework, and gives the user full control over integrations with external packages. For example, rather than abstracting reading from the file system to a plugin, you can use the native Node.js fs package inside getStaticProps / getStaticPaths to read from the file system.
// src/lib/blog.js
// Install gray-matter and date-fns
import matter from 'gray-matter'
import { parseISO, format } from 'date-fns'
import fs from 'fs'
import { join } from 'path'
// Add markdown files in `src/content/blog`
const postsDirectory = join(process.cwd(), 'src', 'content', 'blog')
export function getPostBySlug(slug) {
const realSlug = slug.replace(/\.md$/, '')
const fullPath = join(postsDirectory, `${realSlug}.md`)
const fileContents = fs.readFileSync(fullPath, 'utf8')
const { data, content } = matter(fileContents)
const date = format(parseISO(data.date), 'MMMM dd, yyyy')
return { slug: realSlug, frontmatter: { ...data, date }, content }
}
export function getAllPosts() {
const slugs = fs.readdirSync(postsDirectory)
const posts = slugs.map((slug) => getPostBySlug(slug))
return posts
}
Next.js has a built-in Image Component and Automatic Image Optimization.
The Next.js Image Component, next/image, is an extension of the HTML <img> element, evolved for the modern web.
The Automatic Image Optimization allows for resizing, optimizing, and serving images in modern formats like WebP when the browser supports it. This avoids shipping large images to devices with a smaller viewport. It also allows Next.js to automatically adopt future image formats and serve them to browsers that support those formats.
Instead of optimizing images at build time, Next.js optimizes images on-demand, as users request them. Unlike static site generators and static-only solutions, your build times aren't increased, whether shipping 10 images or 10 million images.
This means you can remove common Gatsby plugins like:
gatsby-imagegatsby-transformer-sharpgatsby-plugin-sharpInstead, use the built-in next/image component and Automatic Image Optimization.
The
next/imagecomponent's default loader is not supported when usingnext export. However, other loader options will work.
import Image from 'next/image'
import profilePic from '../public/me.png'
export default function Home() {
return (
<>
<h1>My Homepage</h1>
<Image
src={profilePic}
alt="Picture of the author"
// When "responsive", similar to "fluid" from Gatsby
// When "intrinsic", similar to "fluid" with maxWidth from Gatsby
// When "fixed", similar to "fixed" from Gatsby
layout="responsive"
// Optional, similar to "blur-up" from Gatsby
placeholder="blur"
// Optional, similar to "width" in Gatsby GraphQL
width={500}
// Optional, similar to "height" in Gatsby GraphQL
height={500}
/>
<p>Welcome to my homepage!</p>
</>
)
}
With Gatsby, your site's metadata (name, description, etc) is located inside gatsby-config.js. This is then exposed through the GraphQL API and consumed through a pageQuery or a static query inside a component.
With Next.js, we recommend creating a config file similar to below. You can then import this file anywhere without having to use GraphQL to access your site's metadata.
// src/config.js
export default {
title: 'Starter Blog',
author: {
name: 'Lee Robinson',
summary: 'who loves Next.js.',
},
description: 'A starter blog converting Gatsby -> Next.',
social: {
twitter: 'leeerob',
},
}
Most Gatsby examples use react-helmet to assist with adding meta tags for proper SEO. With Next.js, we use next/head to add meta tags to your <head /> element. For example, here's an SEO component with Gatsby:
// src/components/seo.js
import { Helmet } from 'react-helmet'
export default function SEO({ description, title, siteTitle }) {
return (
<Helmet
title={title}
titleTemplate={siteTitle ? `%s | ${siteTitle}` : null}
meta={[
{
name: `description`,
content: description,
},
{
property: `og:title`,
content: title,
},
{
property: `og:description`,
content: description,
},
{
property: `og:type`,
content: `website`,
},
{
name: `twitter:card`,
content: `summary`,
},
{
name: `twitter:creator`,
content: twitter,
},
{
name: `twitter:title`,
content: title,
},
{
name: `twitter:description`,
content: description,
},
]}
/>
)
}
And here's the same example using Next.js, including reading from a site config file.
// src/components/seo.js
import Head from 'next/head'
import config from '../config'
export default function SEO({ description, title }) {
const siteTitle = config.title
return (
<Head>
<title>{`${title} | ${siteTitle}`}</title>
<meta name="description" content={description} />
<meta property="og:type" content="website" />
<meta property="og:title" content={title} />
<meta property="og:description" content={description} />
<meta property="og:site_name" content={siteTitle} />
<meta property="twitter:card" content="summary" />
<meta property="twitter:creator" content={config.social.twitter} />
<meta property="twitter:title" content={title} />
<meta property="twitter:description" content={description} />
</Head>
)
}
Take a look at this pull request for more details on how an app can be migrated from Gatsby to Next.js. If you have questions or if this guide didn't work for you, feel free to reach out to our community on GitHub Discussions.