Lazy Loading

Homepage Glossary Lazy Loading

Lazy Loading is a popular web page optimization technique that helps improve site loading speed and performance. Let’s examine what it is, how it works, and why it’s important for SEO.

What is Lazy Loading?

Lazy Loading is a technique where resources (e.g., images, videos, or other page elements) are loaded only when needed. This means content is not loaded all at once, but rather when a user scrolls and the element becomes visible.
This technique helps reduce page load time by speeding up the initial page load and decreasing server load.

Why Use Lazy Loading?

Faster Page Loading. Lazy Loading allows loading only the elements visible on the screen, thereby reducing the initial page load time.
Reduced Server Load. Instead of loading all resources at once, the system loads only those needed at that moment.
Optimization for Mobile Devices. Mobile internet speeds are often slower, and Lazy Loading helps minimize data usage.
Improved User Experience (UX). Faster page loading, especially for media content (images, videos), significantly enhances site perception.
Positive SEO Impact. Google considers loading time a ranking factor, so fast-loading pages may have advantages in search results.

How Does Lazy Loading Work?

Initial Page Load. When the site first loads, only the content visible to the user is downloaded.
Page Scrolling. As the user scrolls down the page, the browser starts loading resources that become visible (e.g., images or videos located lower in the document).
Delayed Loading. Content that is outside the user’s viewport is not loaded until it’s needed.

Example of Implementing Lazy Loading for Images

HTML with a standard <img> tag:

html

HTML with Lazy Loading:
To implement Lazy Loading, add the loading=”lazy” attribute to the <img> tag:

html

This attribute tells the browser to load the image only when it becomes visible on the screen.

Using Lazy Loading for Videos

If your site has videos, you can also load them lazily:

html

Your browser does not support the video tag.

</video>

JavaScript Implementation Technique (if loading=”lazy” is not supported)
For browsers that don’t support the loading=”lazy” attribute, you can use JavaScript. Use a library like lazysizes or write your own script to track element visibility.

html

document.addEventListener(“DOMContentLoaded”, function() {

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

const loadImage = (image) => {

image.src = image.dataset.src;

image.removeAttribute(“data-src”);

};

const imageInViewport = (image) => {

const rect = image.getBoundingClientRect();

return rect.top <= window.innerHeight && rect.bottom >= 0;

};

const handleLazyLoad = () => {

images.forEach(image => {

if (imageInViewport(image)) {

loadImage(image);

}

});

};

window.addEventListener(“scroll”, handleLazyLoad);

handleLazyLoad(); // Initial check for images in the viewport

});

</script>

Advantages of Lazy Loading

Faster Page Load Times. Lazy Loading helps pages load faster, which can reduce bounce rates.
Reduced Data Usage. On mobile devices and slow connections, this technique saves data and loads only the important content quickly.
Improved SEO Rankings. Fast loading times impact Core Web Vitals, which can improve search result positions.
Site Performance Optimization. Especially beneficial for sites with a lot of media content, such as online stores, blogs, news portals, etc.

When NOT to Use Lazy Loading

For Critical Content. If a page has important content that must be visible from the start (e.g., buttons, forms), avoid applying Lazy Loading to such elements.
SEO Pages Without Media. If your page doesn’t contain many images, videos, or other heavy content, using Lazy Loading may not be beneficial.
For Content That Should Be Visible Immediately. For some content types, such as the site header, navigation, or company information, delayed loading can harm the user experience.

Impact on SEO and Google

Core Web Vitals. Lazy Loading helps improve two of the three Core Web Vitals metrics — LCP and CLS, which favorably impacts a site’s search rankings.
User Experience. Faster-loading pages improve the first user impression, as pages appear responsive more quickly.
Search Engine Interpretation. Google and other search engines have learned to index content loaded via Lazy Loading, so with proper implementation, there will be no issues with the visibility of such pages in search results.

Summary

Lazy Loading is a powerful tool for improving web page performance and user convenience. Using deferred loading helps accelerate page loads, conserve resources, and improve SEO. This technique is especially important for sites with a lot of media content, such as images and videos.