Programmatic navigation (useRouter) in NextJS - Performance & Optimization

Performance: Programmatic navigation (useRouter)

MEDIUM IMPACT

This affects page load speed and interaction responsiveness by controlling client-side navigation without full page reloads.

Navigating between pages in a Next.js app

NextJS

import { useRouter } from 'next/router';
const router = useRouter();
router.push('/about');

Performs client-side navigation without full reload, preserving state and faster rendering.

📈 Performance GainNon-blocking navigation, reduces load time by 200-500ms, improves INP

Navigating between pages in a Next.js app

NextJS

window.location.href = '/about';

Triggers a full page reload, blocking rendering and losing React state.

📉 Performance CostBlocks rendering for 200-500ms depending on network, triggers full reload

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
window.location.href navigation	Full DOM reload	Multiple reflows	High paint cost	[X] Bad
useRouter.push navigation	Partial DOM update	Minimal reflows	Low paint cost	[OK] Good

Rendering Pipeline

Programmatic navigation with useRouter updates the URL and fetches only the changed page data, avoiding full reload and reinitializing the React app.

→JavaScript Execution

→Network Fetch

→DOM Update

→Paint

→Composite

⚠️ BottleneckNetwork Fetch for new page data

Core Web Vital Affected

INP

This affects page load speed and interaction responsiveness by controlling client-side navigation without full page reloads.

Optimization Tips

1Avoid full page reloads for navigation to improve interaction speed.

2Use useRouter.push for client-side navigation in Next.js apps.

3Prefetch pages and use shallow routing to minimize network delays.

Performance Quiz - 3 Questions

What is the main performance benefit of using useRouter.push over window.location.href in Next.js?

A It disables network requests

B It reduces JavaScript bundle size

C It avoids full page reloads, improving interaction speed

D It automatically caches all pages

DevTools: Performance

How to check: Record a session while navigating using window.location.href vs useRouter.push. Compare time between input and next paint.

What to look for: Look for long tasks and full page reloads in the timeline for window.location.href; faster interaction and partial updates for useRouter.

Practice

1. What does the useRouter hook from next/navigation allow you to do in a Next.js app?

easy

A. Navigate between pages programmatically using code

B. Automatically reload the page on data change

C. Fetch data from an API endpoint

D. Style components with CSS modules

Solution

1. Step 1: Understand the purpose of useRouter

   The useRouter hook provides methods to change pages in code, not by user clicking links.

2. Step 2: Identify what useRouter does not do

   It does not handle data fetching, styling, or auto-reloading pages.

3. Final Answer:

   Navigate between pages programmatically using code -> Option A

4. Quick Check:

   useRouter = programmatic navigation [OK]

Hint: useRouter lets you move pages by code, not by clicking [OK]

Common Mistakes:

• Confusing useRouter with data fetching hooks
• Thinking useRouter styles components
• Assuming useRouter reloads pages automatically

2. Which of the following is the correct way to import useRouter from Next.js 14+ for programmatic navigation?

easy

A. import { useRouter } from 'next/navigation';

B. import useRouter from 'next/navigation';

C. import { useRouter } from 'next/router';

D. import { useRouter } from 'next/navigation/useRouter';

Solution

1. Step 1: Recall the correct import path for useRouter in Next.js 14+

   In Next.js 14+, useRouter is imported from next/navigation, not next/router.

2. Step 2: Check syntax correctness

   import { useRouter } from 'next/navigation'; uses named import from the correct module. import useRouter from 'next/navigation'; misses braces, causing syntax error. import { useRouter } from 'next/navigation/useRouter'; uses a wrong path.

3. Final Answer:

   import { useRouter } from 'next/navigation'; -> Option A

4. Quick Check:

   Correct import = import { useRouter } from 'next/navigation'; [OK]

Hint: Use named import from 'next/navigation' for useRouter [OK]

Common Mistakes:

• Importing from 'next/router' instead of 'next/navigation'
• Missing curly braces in import
• Using incorrect import paths

3. Given this code snippet in a Next.js component, what will happen when the button is clicked?

import { useRouter } from 'next/navigation';

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

medium

A. The page will navigate to '/about' replacing the current history entry

B. The page will reload but stay on the same URL

C. The page will navigate to '/about' adding a new entry in browser history

D. Nothing happens because router.push is invalid

Solution

1. Step 1: Understand router.push behavior

   The router.push('/about') method navigates to the '/about' page and adds a new entry in the browser history stack.

2. Step 2: Confirm the code triggers navigation on button click

   The button's onClick calls router.push correctly, so navigation happens as expected.

3. Final Answer:

   The page will navigate to '/about' adding a new entry in browser history -> Option C

4. Quick Check:

   router.push adds history entry = The page will navigate to '/about' adding a new entry in browser history [OK]

Hint: router.push adds new history entry and navigates [OK]

Common Mistakes:

• Confusing router.push with router.replace
• Thinking router.push reloads current page
• Assuming router.push does nothing without await

4. Identify the error in this Next.js component using useRouter for navigation:

import { useRouter } from 'next/navigation';

export default function Page() {
  const router = useRouter;
  return (
    <button onClick={() => router.push('/contact')}>Contact</button>
  );
}

medium

A. useRouter should be imported from 'next/router'

B. router.push should be router.replace

C. Button onClick should be onClick={router.push('/contact')}

D. Missing parentheses when calling useRouter hook

Solution

1. Step 1: Check how useRouter is assigned

   The code assigns const router = useRouter; without calling it as a function. It should be useRouter().

2. Step 2: Verify other parts

   router.push is valid for navigation. onClick syntax is correct. Import path is correct.

3. Final Answer:

   Missing parentheses when calling useRouter hook -> Option D

4. Quick Check:

   useRouter must be called as a function [OK]

Hint: Always call useRouter() with parentheses [OK]

Common Mistakes:

• Assigning useRouter without parentheses
• Using router.push incorrectly in onClick
• Importing useRouter from wrong module

5. You want to navigate to a new page without adding a new entry in the browser history (so the back button skips the current page). Which method of useRouter should you use and how?

const router = useRouter();
// Your code here

hard

A. Use router.push('/newpage') to add a new history entry

B. Use router.replace('/newpage') to replace current history entry

C. Use router.reload() to reload current page

D. Use router.back() to go back to previous page

Solution

1. Step 1: Understand difference between push and replace

   router.push() adds a new entry to browser history, while router.replace() swaps the current entry.

2. Step 2: Choose method to avoid adding history entry

   To navigate without adding a new history entry, use router.replace('/newpage').

3. Final Answer:

   Use router.replace('/newpage') to replace current history entry -> Option B

4. Quick Check:

   replace swaps history entry = Use router.replace('/newpage') to replace current history entry [OK]

Hint: Use router.replace() to avoid adding history entry [OK]

Common Mistakes:

• Using router.push when replace is needed
• Confusing reload with navigation
• Using router.back instead of forward navigation