Does lazy loading improve SEO?

Yes, it improves page speed which helps SEO.

Can I lazy load videos?

Yes, using preload="none" or JavaScript.

Lazy Loading in Web - Learn WEB-PERFORMANCE-OPTIMIZATION | Revochamp

Name: Lazy Loading in Web
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Author: Revochamp

What is Lazy Loading?

Lazy loading is a technique where non-critical resources are loaded only when they are needed, such as when they appear in the user's viewport.

Why Use Lazy Loading?

Lazy loading reduces initial page load time, saves bandwidth, and improves performance, especially for pages with many images or heavy content.

Basic Example

HTMLRead-only

<img src="image.jpg" loading="lazy" alt="Lazy Image">

<img src="image.jpg" loading="lazy" alt="Lazy Image">

Lazy Loading Images

Modern browsers support native lazy loading using the loading="lazy" attribute.

HTMLRead-only

<img src="photo.webp" loading="lazy" alt="Example">

<img src="photo.webp" loading="lazy" alt="Example">

Lazy Loading with JavaScript

You can use Intersection Observer API to implement custom lazy loading.

JavaScriptRead-only

const images = document.querySelectorAll('img');

const observer = new IntersectionObserver((entries, observer) => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      const img = entry.target;
      img.src = img.dataset.src;
      observer.unobserve(img);
    }
  });
});

images.forEach(img => observer.observe(img));

const images = document.querySelectorAll('img');

const observer = new IntersectionObserver((entries, observer) => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      const img = entry.target;
      img.src = img.dataset.src;
      observer.unobserve(img);
    }
  });
});

images.forEach(img => observer.observe(img));

Lazy Loading Videos

HTMLRead-only

<video controls preload="none">
  <source src="video.mp4" type="video/mp4">
</video>

<video controls preload="none">
  <source src="video.mp4" type="video/mp4">
</video>

Benefits of Lazy Loading

Faster initial page load
Reduced bandwidth usage
Better user experience
Improved SEO performance

When Not to Use Lazy Loading

For above-the-fold content
For critical UI elements
For important hero images

Best Practices

Use native lazy loading where possible
Provide placeholder or skeleton UI
Combine with image optimization (WebP)
Avoid lazy loading critical resources

Common Mistakes

Lazy loading everything including critical content
Not providing fallback for unsupported browsers
Using heavy JavaScript unnecessarily
Forgetting alt attributes for images

Conclusion

Lazy loading is a powerful technique to improve web performance. When used correctly, it enhances speed, reduces resource usage, and improves user experience.

Test Your Knowledge

of 3

What does lazy loading do?

Loads everything immediately

Loads resources when needed

Blocks rendering

Reduces images

of 3

Which attribute enables lazy loading?

async

defer

lazy

of 3

Which API is used for custom lazy loading?

Fetch API

Intersection Observer

DOM API

Storage API

Test Your Knowledge

of 3

What does lazy loading do?

Loads everything immediately

Loads resources when needed

Blocks rendering

Reduces images

of 3

Which attribute enables lazy loading?

async

defer

lazy

of 3

Which API is used for custom lazy loading?

Fetch API

Intersection Observer

DOM API

Storage API

Lazy Loading in Web

Lazy Loading in Web

What is Lazy Loading?

Why Use Lazy Loading?

Basic Example

Lazy Loading Images

Lazy Loading with JavaScript

Lazy Loading Videos

Benefits of Lazy Loading

When Not to Use Lazy Loading

Best Practices

Common Mistakes

Conclusion

Try it yourself

Test Your Knowledge

Frequently Asked Questions

Need help?

Lazy Loading in Web

Lazy Loading in Web

What is Lazy Loading?

Why Use Lazy Loading?

Basic Example

Lazy Loading Images

Lazy Loading with JavaScript

Lazy Loading Videos

Benefits of Lazy Loading

When Not to Use Lazy Loading

Best Practices

Common Mistakes

Conclusion

Try it yourself

Test Your Knowledge

Frequently Asked Questions

Need help?