Responsive images in NextJS - Mini Project: Build & Apply

Responsive images with Next.js

📖 Scenario: You are building a simple Next.js app that shows a product image. You want the image to load quickly and look good on all screen sizes by using responsive images.

🎯 Goal: Create a Next.js component that displays a responsive product image using the built-in next/image component with different sizes for mobile, tablet, and desktop screens.

📋 What You'll Learn

Use the next/image component to display the image

Set the src to '/images/product.jpg'

Add an alt text 'Product Image' for accessibility

Use the sizes attribute to specify image widths for different screen sizes

Set the width and height props to 800 and 600 respectively

💡 Why This Matters

🌍 Real World

Responsive images improve website speed and user experience on phones, tablets, and desktops by loading the right image size.

💼 Career

Knowing how to use Next.js Image component for responsive images is essential for frontend developers working on modern React and Next.js projects.

1

Setup the Next.js Image import and basic component

Import the Image component from next/image and create a functional component called ProductImage that returns an empty fragment <></>.

NextJS

import Image from 'next/image'

export default function ProductImage() {
  return 
  // Your code here
}

Hint

Use import Image from 'next/image' at the top. Then create a function ProductImage that returns an empty React fragment.

2

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

Inside the ProductImage component, add the <Image> component with src='/images/product.jpg', alt='Product Image', width={800}, and height={600}.

NextJS

import Image from 'next/image'

export default function ProductImage() {
  return (
    // Add Image component here with src, alt, width, and height
  )
}

Hint

Use the Image component with the exact props: src='/images/product.jpg', alt='Product Image', width={800}, and height={600}.

3

Add the sizes attribute for responsive image widths

Add the sizes attribute to the <Image> component with the value '(max-width: 600px) 100vw, (max-width: 1200px) 50vw, 33vw' to specify image widths for mobile, tablet, and desktop screens.

NextJS

import Image from 'next/image'

export default function ProductImage() {
  return (
    
  )
}

Hint

The sizes attribute helps the browser pick the right image size for different screen widths. Use the exact string given.

4

Wrap the Image in a responsive container with semantic HTML

Wrap the <Image> component inside a <section> element with an aria-label of 'Product image section' to improve accessibility and semantic structure.

NextJS

import Image from 'next/image'

export default function ProductImage() {
  return (
    // Wrap Image in a section with aria-label
  )
}

Hint

Use a <section> tag with aria-label='Product image section' wrapping the <Image> component.

Practice

1. What is the main benefit of using responsive images in a Next.js app?

easy

A. They load the right image size for different screen widths, improving speed.

B. They automatically add captions to images.

C. They convert images to black and white on small screens.

D. They disable images on mobile devices to save data.

Solution

1. Step 1: Understand responsive images purpose

   Responsive images adjust to screen size to load faster and look better.

2. Step 2: Identify Next.js Image component benefit

   Next.js Image component helps load the right image size automatically.

3. Final Answer:

   They load the right image size for different screen widths, improving speed. -> Option A

4. Quick Check:

   Responsive images = load right size fast [OK]

Hint: Responsive images adapt size to screen for speed [OK]

Common Mistakes:

• Thinking responsive images add captions automatically
• Believing images turn black and white on small screens
• Assuming images are disabled on mobile devices

2. Which is the correct way to import and use the Next.js Image component for responsive images?

easy

A. import Image from 'next/image';

B. import { Image } from 'react';

C. import Img from 'next/image';

D. import Image from 'next/image';

Solution

1. Step 1: Check import syntax

   Next.js Image is imported as default from 'next/image'. So, import Image from 'next/image' is correct.

2. Step 2: Check usage with required props

   Image requires src, width, height, and alt for accessibility and layout.

3. Final Answer:

   import Image from 'next/image'; <Image src='/pic.jpg' width={500} height={300} alt='pic' /> -> Option A

4. Quick Check:

   Correct import + width/height + alt = import Image from 'next/image'; [OK]

Hint: Next.js Image needs import, src, width, height, alt [OK]

Common Mistakes:

• Importing Image from 'react' instead of 'next/image'
• Omitting width and height props
• Using wrong component name like Img

3. What will be the behavior of this Next.js Image component?

import Image from 'next/image';
export default function Photo() {
  return (
    <Image
      src='/photo.jpg'
      alt='A photo'
      sizes='(max-width: 600px) 100vw, 50vw'
      width={800}
      height={600}
    />
  );
}

medium

A. Loads image only on screens wider than 600px.

B. Always loads image at 800x600 pixels regardless of screen size.

C. Throws an error because sizes prop is invalid.

D. Loads 100% viewport width image on screens 600px or smaller, else 50% viewport width.

Solution

1. Step 1: Understand sizes prop usage

   The sizes prop defines image display width based on screen width media queries.

2. Step 2: Interpret sizes value

   For screens max 600px wide, image uses 100vw (full viewport width). Otherwise, 50vw (half viewport width).

3. Final Answer:

   Loads 100% viewport width image on screens 600px or smaller, else 50% viewport width. -> Option D

4. Quick Check:

   Sizes prop controls image width by screen size [OK]

Hint: Sizes prop sets image width per screen size [OK]

Common Mistakes:

• Thinking sizes sets image pixel dimensions directly
• Assuming sizes prop causes error
• Believing image loads only on wide screens

4. Identify the error in this Next.js Image usage:

import Image from 'next/image';
export default function Banner() {
  return (
    <Image
      src='/banner.png'
      alt='Banner'
      width='100%'
      height='300'
    />
  );
}

medium

A. alt text is missing.

B. src path must be an external URL.

C. width should be a number, not a string with '%'.

D. height cannot be set with a number.

Solution

1. Step 1: Check width prop type

   Next.js Image expects width as a number (pixels), not a string with '%'.

2. Step 2: Verify other props

   alt is present, src can be local path, height as number is valid.

3. Final Answer:

   width should be a number, not a string with '%'. -> Option C

4. Quick Check:

   Width must be numeric pixels [OK]

Hint: Width and height props must be numbers, not strings [OK]

Common Mistakes:

• Using percentage strings for width or height
• Thinking alt text is optional
• Believing src must be external URL

5. You want to optimize images for a blog with different screen sizes. Which approach correctly uses Next.js Image to load responsive images with accessibility and performance in mind?

hard

A.

B.

C.

D.

Solution

1. Step 1: Check alt text for accessibility

   includes meaningful alt text 'Blog post', improving accessibility.

2. Step 2: Verify sizes and priority usage

   Sizes prop correctly sets image width for small and larger screens. Priority loads important images faster.

3. Step 3: Identify issues in other options

   A lacks alt text and reverses sizes logic, B has empty alt (bad for accessibility), D uses invalid string props for width/height.

4. Final Answer:

   <Image src='/post.jpg' alt='Blog post' width={1200} height={800} sizes='(max-width: 768px) 100vw, 50vw' priority /> -> Option B

5. Quick Check:

   Alt + sizes + priority = best practice [OK]

Hint: Use alt text, sizes, and priority for best responsive images [OK]

Common Mistakes:

• Leaving alt text empty
• Using invalid width/height values
• Incorrect sizes media query order