Image optimization with next/image in NextJS - Mini Project: Build & Apply

Image optimization with next/image

📖 Scenario: You are building a simple Next.js website that shows a product image. You want to use Next.js's built-in image optimization to make the page load faster and look good on all devices.

🎯 Goal: Create a Next.js component that displays an optimized image using the next/image component with proper width, height, and alt text.

📋 What You'll Learn

Import the Image component from next/image

Use the Image component to display an image from the public folder

Set the image src to /product.jpg

Set the image width to 400 and height to 300

Add an alt attribute with the text Product image

💡 Why This Matters

🌍 Real World

Optimizing images on websites improves loading speed and user experience, especially on mobile devices and slow networks.

💼 Career

Knowing how to use Next.js's image optimization is valuable for frontend developers working on performance-focused React applications.

1

Setup the Next.js component

Create a new React functional component called ProductImage that returns an empty fragment <></>.

NextJS

function ProductImage() {
  return ;
  // Your code here
}

Hint

Start by writing a simple React function that returns an empty fragment.

2

Import the Image component

Add an import statement at the top to import Image from next/image.

NextJS

import Image from 'next/image';

function ProductImage() {
  return ;
  // Your code here
}

Hint

Use import Image from 'next/image' to get the optimized image component.

3

Add the Image component with src, width, height, and alt

Inside the ProductImage component's return, replace the empty fragment with the Image component. Set src to "/product.jpg", width to 400, height to 300, and alt to "Product image".

NextJS

import Image from 'next/image';

function ProductImage() {
  return (
    
  );
}

Hint

Use the Image component with the exact props for source, size, and alt text.

4

Export the component as default

Add a default export statement for the ProductImage component at the end of the file.

NextJS

import Image from 'next/image';

function ProductImage() {
  return (
    
  );
}

// Your code here

Hint

Use export default ProductImage; to make the component usable in other files.

Practice

1. What is the main benefit of using next/image in a Next.js project?

easy

A. It only works with SVG images.

B. It converts images to text for SEO purposes.

C. It disables image loading to save bandwidth.

D. It automatically optimizes images for faster loading and better quality.

Solution

1. Step 1: Understand the purpose of next/image

   The next/image component is designed to optimize images automatically, improving loading speed and quality.

2. Step 2: Compare options with the purpose

   Only It automatically optimizes images for faster loading and better quality. correctly describes this benefit. Other options describe unrelated or incorrect features.

3. Final Answer:

   It automatically optimizes images for faster loading and better quality. -> Option D

4. Quick Check:

   Image optimization = D [OK]

Hint: Remember next/image optimizes images automatically [OK]

Common Mistakes:

• Thinking next/image converts images to text
• Believing it disables image loading
• Assuming it only supports SVG

2. Which of the following is the correct way to import and use the Image component from Next.js for image optimization?

easy

A. import { Image } from 'react';

B. import Image from 'next/image';

C. import Img from 'next/image';

D. import Image from 'next/image';

Solution

1. Step 1: Check import syntax

   The correct import for Next.js image optimization is import Image from 'next/image';.

2. Step 2: Verify usage with required props

   The Image component requires src, alt, and explicit width and height for optimization. import Image from 'next/image';
   includes all correctly.

3. Final Answer:

   import Image from 'next/image'; with src, alt, width, and height props -> Option B

4. Quick Check:

   Correct import and props = B [OK]

Hint: Always import Image from 'next/image' with width and height [OK]

Common Mistakes:

• Importing Image from 'react' instead of 'next/image'
• Omitting width and height props
• Using wrong import names

3. What will be the rendered output behavior of this Next.js code snippet?

import Image from 'next/image';

export default function Logo() {
  return (
    <Image src='/logo.png' alt='Company Logo' width={200} height={100} priority />
  );
}

medium

A. The image loads immediately with 200x100 size due to priority prop.

B. The image will not render because priority is invalid.

C. The image loads lazily by default with 200x100 size.

D. The image loads with default size ignoring width and height.

Solution

1. Step 1: Understand the priority prop effect

   The priority prop forces the image to load immediately instead of lazy loading.

2. Step 2: Check width and height usage

   Width and height props set the image size to 200x100 pixels, which will be respected.

3. Final Answer:

   The image loads immediately with 200x100 size due to priority prop. -> Option A

4. Quick Check:

   priority = immediate load = C [OK]

Hint: priority prop disables lazy loading for faster display [OK]

Common Mistakes:

• Assuming priority disables image rendering
• Thinking width and height are ignored
• Confusing lazy loading default behavior

4. Identify the error in this Next.js image usage and how to fix it:

import Image from 'next/image';

export default function Profile() {
  return (
    <Image src='/profile.jpg' alt='User Profile' width='150' height='150' />
  );
}

medium

A. src path must be an external URL, not local path.

B. alt attribute is missing, causing accessibility issues.

C. width and height should be numbers, not strings.

D. Image component must be self-closing with a slash.

Solution

1. Step 1: Check width and height prop types

   Next.js Image requires width and height as numbers, not strings. Here they are strings ('150').

2. Step 2: Correct the prop types

   Remove quotes to pass numbers: width={150} and height={150}.

3. Final Answer:

   width and height should be numbers, not strings. -> Option C

4. Quick Check:

   width/height as numbers = A [OK]

Hint: Use curly braces for numeric width and height [OK]

Common Mistakes:

• Passing width and height as strings
• Ignoring alt attribute importance
• Thinking local src paths are invalid

5. You want to optimize multiple images with different sizes responsively using next/image. Which approach correctly uses the sizes attribute to serve appropriate image sizes on different screen widths?

hard

A. <Image src='/photo.jpg' alt='Photo' width={800} height={600} sizes='(max-width: 600px) 100vw, 50vw' />

B. <Image src='/photo.jpg' alt='Photo' width='800' height='600' sizes='100vw' />

C. <Image src='/photo.jpg' alt='Photo' width={800} height={600} sizes='(min-width: 600px) 100vw, 50vw' />

D. <Image src='/photo.jpg' alt='Photo' width={800} height={600} />

Solution

1. Step 1: Understand the sizes attribute usage

   The sizes attribute defines image display sizes for different viewport widths using media queries.

2. Step 2: Analyze the options

   <Image src='/photo.jpg' alt='Photo' width={800} height={600} sizes='(max-width: 600px) 100vw, 50vw' /> correctly uses (max-width: 600px) 100vw, 50vw meaning full viewport width on small screens, half on larger screens. This is a common responsive pattern.

3. Final Answer:

   Use sizes='(max-width: 600px) 100vw, 50vw' with numeric width and height. -> Option A

4. Quick Check:

   Responsive sizes attribute = A [OK]

Hint: Use sizes with max-width media query for responsive images [OK]

Common Mistakes:

• Passing width and height as strings
• Using min-width instead of max-width incorrectly
• Omitting sizes attribute for responsiveness