Pre-rendering and Data Fetching

Two Forms of Pre-rendering

Next.js has two forms of pre-rendering: Static Generation and Server-side Rendering. The difference is in when it generates the HTML for a page.

  • Static Generation is the pre-rendering method that generates the HTML at build time. The pre-rendered HTML is then reused on each request.
  • Server-side Rendering is the pre-rendering method that generates the HTML on each request.

In development mode (when you run npm run dev or yarn dev), pages are pre-rendered on every request. This also applies to Static Generation to make it easier to develop. When going to production, Static Generation will happen once, at build time, and not on every request.

Per-page Basis

Importantly, Next.js lets you choose which pre-rendering form to use for each page. You can create a "hybrid" Next.js app by using Static Generation for most pages and using Server-side Rendering for others.

When to Use Static Generation v.s. Server-side Rendering

We recommend using Static Generation (with and without data) whenever possible because your page can be built once and served by CDN, which makes it much faster than having a server render the page on every request.

You can use Static Generation for many types of pages, including:

  • Marketing pages
  • Blog posts
  • E-commerce product listings
  • Help and documentation

You should ask yourself: "Can I pre-render this page ahead of a user's request?" If the answer is yes, then you should choose Static Generation.

On the other hand, Static Generation is not a good idea if you cannot pre-render a page ahead of a user's request. Maybe your page shows frequently updated data, and the page content changes on every request.

In that case, you can use Server-side Rendering. It will be slower, but the pre-rendered page will always be up-to-date. Or you can skip pre-rendering and use client-side JavaScript to populate frequently updated data.

We’ll Focus on Static Generation

In this lesson, we’ll focus on Static Generation. On the next page, we’ll talk about Static Generation with and without data.

Quick Review: When would you use Server-side rendering?