How Next.js renders (server-first model)

Introduction

Next.js renders pages first on the server to send ready HTML to the browser. This makes pages load faster and helps search engines understand your site better.

You want your website to load quickly for users on slow connections.

You want your site to be easy for search engines to find and rank.

You want to show content immediately without waiting for JavaScript to load.

You want to keep your page content secure before sending it to the browser.

You want to improve user experience by reducing blank screens during loading.

Syntax

NextJS

export default function Page() {
  return (
    <main>
      <h1>Hello from Server</h1>
    </main>
  )
}

// This component runs on the server first, then sends HTML to the browser.

Next.js uses React components that run on the server first by default.

You can add special functions like getServerSideProps to fetch data on the server before rendering.

Examples

A simple page component rendered on the server first.

NextJS

export default function Home() {
  return <h1>Welcome to Next.js!</h1>
}

This example fetches data on the server before rendering the page.

NextJS

export async function getServerSideProps() {
  return { props: { time: new Date().toISOString() } }
}

export default function TimePage({ time }) {
  return <p>Current server time: {time}</p>
}

This component runs in the browser after the server sends the HTML.

NextJS

'use client'

import { useState } from 'react'

export default function ClientComponent() {
  const [count, setCount] = useState(0)
  return <button onClick={() => setCount(count + 1)}>Clicked {count} times</button>
}

Sample Program

This Next.js page uses getServerSideProps to prepare data on the server. The server sends the complete HTML with the message. The browser shows the message immediately without waiting for JavaScript.

NextJS

import React from 'react'

export async function getServerSideProps() {
  const message = 'Hello from the server!'
  return { props: { message } }
}

export default function Greeting({ message }) {
  return (
    <main>
      <h1>{message}</h1>
      <p>This page was rendered on the server first.</p>
    </main>
  )
}

Important Notes

Server-first rendering means the server creates the HTML before the browser sees it.

After the server sends HTML, React takes over in the browser to make the page interactive.

You can mix server rendering with client-side code for dynamic features.

Summary

Next.js renders pages on the server first to improve speed and SEO.

Use getServerSideProps to fetch data on the server before rendering.

The browser receives ready HTML and then adds interactivity with React.

Practice

1. What is the main reason Next.js renders pages on the server first?

easy

A. To avoid using React components

B. To run JavaScript only on the client

C. To improve page load speed and SEO

D. To prevent any HTML from being sent to the browser

Solution

1. Step 1: Understand server-first rendering purpose

   Next.js renders pages on the server to send fully formed HTML to the browser quickly.

2. Step 2: Connect server rendering to SEO and speed

   Sending ready HTML helps search engines read content and users see pages faster.

3. Final Answer:

   To improve page load speed and SEO -> Option C

4. Quick Check:

   Server-first rendering = better speed and SEO [OK]

Hint: Server rendering means faster pages and better SEO [OK]

Common Mistakes:

• Thinking server rendering delays page load
• Believing React is not used in Next.js
• Assuming HTML is not sent to the browser

2. Which Next.js function is used to fetch data on the server before rendering a page?

easy

A. getServerSideProps

B. componentDidMount

C. useEffect

D. getStaticProps

Solution

1. Step 1: Identify server-side data fetching functions

   Next.js provides getServerSideProps to fetch data on the server at request time.

2. Step 2: Differentiate from other functions

   getStaticProps runs at build time, useEffect and componentDidMount run on client side.

3. Final Answer:

   getServerSideProps -> Option A

4. Quick Check:

   Server data fetch = getServerSideProps [OK]

Hint: Server data fetch uses getServerSideProps [OK]

Common Mistakes:

• Confusing getStaticProps with server-side fetching
• Using client hooks like useEffect for server data
• Thinking componentDidMount runs on server

3. Given this Next.js page code, what will the browser initially receive?

export async function getServerSideProps() {
  return { props: { message: 'Hello from server' } };
}

export default function Page({ message }) {
  return <h1>{message}</h1>;
}

medium

A. HTML with <h1>Hello from server</h1>

B. An empty page with no content

C. JavaScript code only, no HTML

D. A JSON object with the message

Solution

1. Step 1: Understand getServerSideProps role

   This function runs on the server and passes props to the component before rendering.

2. Step 2: Determine what is sent to browser

   The browser receives fully rendered HTML with the message inside an <h1> tag.

3. Final Answer:

   HTML with <h1>Hello from server</h1> -> Option A

4. Quick Check:

   Server props produce HTML output [OK]

Hint: Server props render HTML sent to browser first [OK]

Common Mistakes:

• Expecting raw JavaScript or JSON instead of HTML
• Thinking page is empty initially
• Confusing client-side rendering with server rendering

4. What is wrong with this Next.js page code?

export async function getServerSideProps() {
  const data = await fetch('https://api.example.com/data');
  return { props: { data } };
}

export default function Page({ data }) {
  return <div>{data.title}</div>;
}

medium

A. React components cannot use props

B. getServerSideProps cannot be async

C. Props cannot be passed to components

D. fetch returns a Response object, not JSON data

Solution

1. Step 1: Check fetch usage in getServerSideProps

   fetch returns a Response object; to get JSON, .json() must be called.

2. Step 2: Identify missing JSON parsing

   Without calling await data.json(), data is not the actual JSON, causing errors in rendering.

3. Final Answer:

   fetch returns a Response object, not JSON data -> Option D

4. Quick Check:

   fetch needs .json() to get data [OK]

Hint: Always parse fetch response with .json() in server props [OK]

Common Mistakes:

• Assuming fetch returns JSON directly
• Thinking getServerSideProps can't be async
• Believing props can't be passed to components

5. You want to render a page that shows a list of users fetched from an API on every request. Which Next.js approach correctly ensures the page is server-rendered with fresh data each time?

hard

A. Use getStaticProps to fetch users at build time

B. Use getServerSideProps to fetch users on each request

C. Fetch users inside useEffect in the component

D. Hardcode the user list in the component

Solution

1. Step 1: Understand data freshness needs

   Fetching fresh data on every request requires server-side fetching at request time.

2. Step 2: Match Next.js data fetching methods

   getServerSideProps runs on each request, while getStaticProps runs once at build time.

3. Step 3: Evaluate client-side fetching

   Fetching inside useEffect delays data until after page load, hurting SEO and initial render.

4. Final Answer:

   Use getServerSideProps to fetch users on each request -> Option B

5. Quick Check:

   Fresh server data = getServerSideProps [OK]

Hint: Fresh data each request? Use getServerSideProps [OK]

Common Mistakes:

• Using getStaticProps for dynamic data
• Fetching data only on client side
• Hardcoding data instead of fetching