Router cache on client in NextJS

Introduction

Router cache on client helps your app load pages faster by remembering data and components you already visited. It avoids reloading everything from the server each time.

When users navigate back and forth between pages quickly.

When you want to reduce loading time and improve user experience.

When your app has many pages with repeated visits.

When you want to save bandwidth by not fetching the same data again.

When you want smooth transitions without flickering or delays.

Syntax

NextJS

import { useRouter } from 'next/navigation';

const router = useRouter();

router.prefetch('/page');

router.prefetch() tells Next.js to load the page in the background before the user visits it.

This caching happens automatically for visited pages, but prefetch helps prepare pages early.

Examples

This example preloads the About page so it opens faster when clicked.

NextJS

'use client';

import React from 'react';
import { useRouter } from 'next/navigation';

export default function Home() {
  const router = useRouter();

  // Prefetch about page when component mounts
  React.useEffect(() => {
    router.prefetch('/about');
  }, []);

  return <button onClick={() => router.push('/about')}>Go to About</button>;
}

Here, prefetch is turned off for the Contact link to save bandwidth if you don't expect users to visit it soon.

NextJS

import Link from 'next/link';

export default function Nav() {
  return <nav>
    <Link href="/contact" prefetch={false}>Contact</Link>
  </nav>;
}

Sample Program

This component preloads the About page when the Home page loads. Clicking the button navigates instantly because the page is cached.

NextJS

'use client';

import { useRouter } from 'next/navigation';
import React from 'react';

export default function Home() {
  const router = useRouter();

  React.useEffect(() => {
    // Prefetch the About page to cache it on client
    router.prefetch('/about');
  }, []);

  return (
    <main>
      <h1>Home Page</h1>
      <button onClick={() => router.push('/about')}>Go to About</button>
    </main>
  );
}

Important Notes

Next.js automatically caches pages you visit, so you usually don't need to manage cache manually.

Use router.prefetch() to improve speed for pages users are likely to visit next.

Be mindful of network usage when prefetching many pages.

Summary

Router cache on client speeds up navigation by storing visited pages.

Use router.prefetch() to load pages before users click links.

This improves user experience with faster page loads and smoother transitions.

Practice

1. What is the main purpose of router cache on the client in Next.js?

easy

A. To disable client-side navigation completely

B. To speed up navigation by storing visited pages locally

C. To increase server load by fetching pages repeatedly

D. To prevent users from accessing certain pages

Solution

1. Step 1: Understand router cache concept

   Router cache stores pages visited by the user on the client side to avoid reloading them from the server.

2. Step 2: Identify the effect on navigation speed

   By storing pages locally, navigation becomes faster and smoother because the browser doesn't need to fetch the page again.

3. Final Answer:

   To speed up navigation by storing visited pages locally -> Option B

4. Quick Check:

   Router cache = faster navigation [OK]

Hint: Router cache means storing pages locally for faster navigation [OK]

Common Mistakes:

• Thinking router cache increases server load
• Confusing cache with disabling navigation
• Assuming cache blocks page access

2. Which Next.js router method is used to prefetch a page and cache it on the client?

easy

A. router.prefetch()

B. router.load()

C. router.cache()

D. router.fetch()

Solution

1. Step 1: Recall Next.js router methods

   Next.js provides a method called router.prefetch() to load pages in advance.

2. Step 2: Match method to caching behavior

   router.prefetch() loads the page and stores it in the client cache for faster navigation.

3. Final Answer:

   router.prefetch() -> Option A

4. Quick Check:

   Prefetch method caches pages [OK]

Hint: Prefetch means load ahead to cache page [OK]

Common Mistakes:

• Using non-existent methods like router.load()
• Confusing fetch with prefetch
• Assuming cache() is a router method

3. Given this code snippet in a Next.js component:

import { useRouter } from 'next/router';

export default function Home() {
  const router = useRouter();
  router.prefetch('/about');
  return <button onClick={() => router.push('/about')>Go to About</button>;
}

What happens when the user clicks the button?

medium

A. An error occurs because prefetch cannot be called inside the component

B. The /about page reloads from the server every time

C. The button does nothing because prefetch disables navigation

D. The /about page loads instantly from client cache

Solution

1. Step 1: Understand router.prefetch usage

   The code calls router.prefetch('/about') inside the component, which loads and caches the /about page on the client.

2. Step 2: Analyze button click behavior

   When clicking the button, router.push('/about') navigates to the cached page, making the load instant without server fetch.

3. Final Answer:

   The /about page loads instantly from client cache -> Option D

4. Quick Check:

   Prefetch + push = instant load [OK]

Hint: Prefetch before push means instant page load [OK]

Common Mistakes:

• Thinking prefetch disables navigation
• Assuming page reloads from server always
• Believing prefetch causes errors inside components

4. Identify the error in this Next.js code that tries to prefetch a page:

import { useRouter } from 'next/router';

export default function Page() {
  const router = useRouter();

  function handleClick() {
    router.prefetch('/contact')
  }

  return <button onClick={handleClick}>Load Contact</button>;
}

medium

A. router.prefetch must be called outside event handlers

B. Missing semicolon after router.prefetch call causes syntax error

C. No error; code correctly prefetches on button click

D. useRouter cannot be used inside functional components

Solution

1. Step 1: Check router.prefetch usage

   Calling router.prefetch('/contact') inside an event handler is valid and triggers prefetch when the button is clicked.

2. Step 2: Verify syntax and hooks usage

   The code has correct syntax and useRouter is properly used inside the functional component.

3. Final Answer:

   No error; code correctly prefetches on button click -> Option C

4. Quick Check:

   Prefetch in event handler is valid [OK]

Hint: Prefetch can run inside event handlers safely [OK]

Common Mistakes:

• Thinking prefetch must run only on mount
• Assuming missing semicolon breaks code
• Believing useRouter is invalid in functional components

5. You want to improve user experience by preloading multiple pages on client side in Next.js. Which approach correctly prefetches pages for /about and /contact when the homepage loads?

hard

A. Call router.prefetch('/about') and router.prefetch('/contact') inside a useEffect hook with empty dependency array

B. Call router.prefetch('/about') and router.prefetch('/contact') directly in the component body

C. Call router.push('/about') and router.push('/contact') inside useEffect

D. Use getServerSideProps to prefetch pages on the server

Solution

1. Step 1: Understand prefetch timing

   Prefetching pages on client should happen after component mounts to avoid blocking rendering, so useEffect with empty dependencies is ideal.

2. Step 2: Avoid direct calls in component body or pushing pages

   Calling router.prefetch() directly in the component body runs on every render, which is inefficient. Using router.push() navigates instead of prefetching. getServerSideProps runs on server, not client cache.

3. Final Answer:

   Call router.prefetch('/about') and router.prefetch('/contact') inside a useEffect hook with empty dependency array -> Option A

4. Quick Check:

   Prefetch in useEffect = best practice [OK]

Hint: Prefetch pages inside useEffect to run once on mount [OK]

Common Mistakes:

• Prefetching directly in component body causing repeated calls
• Using router.push instead of prefetch
• Trying to prefetch on server side with getServerSideProps