Comparing Next.js Vs Astro Rendering Strategies

Next.js is one of the most popular JavaScript frameworks and has been for a few years. On the flip side, Astro is a newer framework that has built a lot of momentum in just the last year. That said, both frameworks provide lots of flexibility in terms of rendering web pages. In this article, we will explore and compare the different ways to render content using Astro and Next.js. By the end, you’ll have a better understanding of the strengths and differences of each framework with regards to rendering strategies.

Static Site Generation (SSG)

With SSG, pages are pre-rendered during the build process and served as static HTML files. This approach offers improved performance and SEO benefits. Both Astro and Next.js support SSG. Here’s a quick comparison.

With Next.js, to query content for a static page, you need to export a getStaticProps function inside of your page component.

export async function getStaticProps() {
  const posts = await getPosts();

  return {
    props: {
      posts,
    },
  };
}

Additionally, if you need to generate dynamic URL paths based on your static content, you can export the getStaticPaths function.

export const getStaticPaths = async () => {
  return {
    paths: [
      { params: { ... } },
      { params: { ... } },
    ],
  };
};

To accomplish this same idea is even simpler in Astro since Astro builds statically generated content by default. This means you don’t have to export a specific function to generate static content. Instead, you can simply use the fetch function to query your data like so:

const response = await fetch('...');

This data will then be available to render in your static page. If you need to generate URL paths based on your static content, you can export a getStaticPaths function similar to Next.js.

export async function getStaticPaths() {
  return [
    { params: { ... } },
    { params: { ... } },
  ];
}

Server-Side Rendering (SSR)

As opposed to SSG, SSR content is generated on the server at request time. This means when the request for a page comes in, the server will generate the HTML for that page and send it back to the client. This approach is ideal for dynamic content that needs to be personalized for each user. Both Astro and Next.js support SSR. Here’s a quick comparison.

With Next.js, to query content for a server rendered page, you need to export a getServerSideProps function inside of your page component.

export async function getServerSideProps() {
  const posts = await getPosts();

  return {
    props: {
      posts,
    },
  };
}

With Astro, it’s a bit different. Because Astro is configured for SSG by default, if you want to render content on the server, you have to enable SSR in your Astro config file by defining the output property to be server.

import { defineConfig } from 'astro/config';

export default defineConfig({
  output: 'server',
});

By configuring your output as server, all of your pages will be rendered on the server instead of statically. If you want to render some pages on the server and some pages statically, you have to explicitly define that for individual pages (more on this shortly).

From there, all of your pages that query data will all do so on the server. This means you don’t have to export a specific function to generate server rendered content. Instead, you can simply use the fetch function to query your data the same as above:

const response = await fetch('...');

Hydration

Earlier, we mentioned that Astro doesn’t send JavaScript to the browser by default. This isn’t the case with Next.js. Although Next.js can handle both statically generated and server rendered content, it still sends JavaScript to the browser every time. This client-side JavaScript is used to do a couple of things:

• Loading additional data
• Handling interactive JavaScript
• Handling client-side routing
• Handling client-side state management

This process of loading JavaScript on the browser after the initial page render is called Hydration. This enables the full power of React in the browser.

Although Astro doesn’t support hydration default, you can enable frontend JavaScript by using the client directive on a given component. This allows you to control when and if JavaScript is loaded into the browser. On really neat aspect of this in Astro is the fact that you can use components written in other libraries: React, Vue, Svelte, etc.

Astro also introduces an important concept called Astro Islands. This essentially means that you can load JavaScript in certain pieces of your application. In other words, you have the ability to load JavaScript in certain “islands” but not others.

For example, you might have a few components that need JavaScript like a header, carousel, model, etc. You can choose to load JavaScript for these specific components, but not for the rest of the page. This is a really powerful concept that allows you to optimize your application for performance.

Hybrid Rendering

In short, both of these frameworks allow you to mix and match all of the strategies above 🥰

Conclusion

Next.js and Astro are both incredible frameworks that have immense flexibility and power. Hopefully this article has helped you understand the different ways to render content using Astro and Next.js. If you have any questions, feel free to reach out on Twitter!