Ever noticed how some websites load super fast, even with tons of images and videos? The secret is Lazy Loading—a technique that loads content only when needed. This improves performance, saves bandwidth, and enhances user experience.

In this post, you'll learn:

✅ How to lazy load images, videos, and iframes

✅ Using the Intersection Observer API (with code examples)

✅ Best practices to prevent content visibility delays

Let’s dive in! 🔥

📷 How to Lazy Load Images

Instead of loading all images at once, lazy loading loads them only when they appear in the viewport. You can enable it easily using the loading="lazy" attribute:

🔗 More on Lazy Loading Images: MDN Docs

🎥 Lazy Load Videos & Iframes

Videos and iframes can drastically slow down your page. Use loading="lazy" for iframes and defer video loading using JavaScript.

For iframes:

<iframe src="https://www.youtube.com/embed/example" loading="lazy"></iframe>

For videos:

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

🔗 Optimize Video Performance: Google Web.dev Guide

🕵️‍♂️ Using the Intersection Observer API

For advanced control, use the Intersection Observer API to detect when elements enter the viewport and load them dynamically.

Here’s how:

const images = document.querySelectorAll("img[data-src]");

const observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry.isIntersecting) {
const img = entry.target;
img.src = img.dataset.src;
img.removeAttribute("data-src");
observer.unobserve(img);
}
});
}, { rootMargin: "0px", threshold: 0.1 });

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

🔗 Full Guide on Intersection Observer API: MDN Docs

⚡ Best Practices to Avoid Content Visibility Delays

Lazy loading is great, but poor implementation can cause elements to appear late or shift unexpectedly. Follow these tips:

✅ Use placeholders: Prevent layout shifts with a fixed height and width for images.

✅ Combine lazy loading with preload: Preload critical assets while deferring others.

✅ Optimize images: Compress images with TinyPNG or Squoosh.

✅ Test performance: Use Google PageSpeed Insights to analyze lazy loading effectiveness.

🔥 Your Thoughts?

Have you implemented lazy loading in your projects? What techniques do you use to optimize performance? Drop your thoughts in the comments! 💬👇
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