How to Implement Lazy Loading Images for SEO

We've all been there. You click on a website and wait... and wait. Most people won't wait more than 3 seconds for a site to load. In fact, over 53% of mobile users will leave if it takes too long (Google). That's bad news for your website.

 

The problem? Most websites load all their pictures at once. Even the ones you can't see yet. Images account for over 50% of a webpage's size. This makes everything slower. Slow websites get fewer visitors from Google, and people leave faster.

 

But there's an easy fix: lazy loading. Instead of loading every picture right away, lazy loading only shows images when you scroll to them. It's like reading a book — you only see the page you're on. This technique makes websites load much faster. And faster websites mean happier visitors, more engagement and ultimately better Google rankings.

 

In this guide, we'll show you exactly how to add lazy loading to your website. We'll cover simple methods for beginners and tips for experts. You'll learn how to speed up your site today.

What Is Lazy Loading?

Imagine walking through a buffet where food only appears as you reach each station. That's exactly how lazy loading works for websites!

 

Lazy loading is a smart way to load pictures on your website. Instead of showing all images at once (which slows everything down), it only loads the images you can see right now. As you scroll down the page, new images load just before they come into view.

 

Here's how it works in simple terms:

 

• When you first visit a page, only the visible images load (what you see without scrolling)

• As you scroll down, the browser quietly loads other images just before they appear

• Images at the very bottom don't load until you get there

 

This method makes websites:

 

• Loads faster when first opened

• Use less data (great for mobile users)

• Feel smoother when scrolling

Why Lazy Loading Matters for SEO

Lazy loading isn't just convenient. It is an SEO game-changer. Here's why:

Boosts Google Rankings

Google prioritizes fast sites. Lazy loading improves Core Web Vitals scores (especially LCP) by up to 40%, helping you rank higher.

Keeps Visitors Engaged

Medium reduced bounce rates by 23% after implementing lazy loading. Faster-loading pages mean more visitors stay longer.

Saves Precious Bandwidth

Mobile users save up to 50% on data usage. Which is crucial for emerging markets with limited data plans.

Improves Crawl Efficiency

Googlebot indexes prioritized content faster when resources aren't wasted loading offscreen images.

 

Further Read: What is Crawl Budget? How to Save it and Solve the Indexing Problem

How to Implement Lazy Loading: Step-by-Step Guide

Lazy loading can be implemented in multiple ways—whether you're a beginner using simple HTML, a developer needing advanced control, or a WordPress user looking for a plugin solution. Below, we break down each method with detailed instructions, code examples, and key benefits.

4.1. Native HTML

The simplest way to enable lazy loading is by using the native HTML loading="lazy" attribute. This method requires no JavaScript and is supported by all modern browsers (Chrome, Firefox, Edge, Safari).

 

Using this method is quite simple. Just add the loading="lazy" attribute to your <img> tags:

 

<img 

  src="image.jpg" 

  alt="A descriptive keyword-rich alt text for SEO" 

  loading="lazy" 

  width="600" 

  height="400"

>

 

Pros: 

 

• Zero JavaScript is needed. No extra code slows down your site.

• The system performs automatic browser optimization. Images load just before they enter the viewport.

• It is very SEO-friendly. Googlebot understands lazy-loaded content.

 

Cons: 

 

• No fine-tuned control (e.g., custom loading thresholds).

• Very old browsers do not support this feature, but they will revert to normal loading.

4.2. JavaScript

If you need more customization (like lazy loading background images, videos, or dynamically loaded content), JavaScript solutions are the way to go.

Option A: IntersectionObserver API

The IntersectionObserver API is a modern way to detect when an element enters the viewport.

 

Example Code

 

document.addEventListener("DOMContentLoaded", function() {

  const images = document.querySelectorAll("img.lazy");

  

  const observer = new IntersectionObserver((entries) => {

    entries.forEach((entry) => {

      if (entry.isIntersecting) {

        const img = entry.target;

        img.src = img.dataset.src;

        observer.unobserve(img);

      }

    });

  }, { threshold: 0.1 }); // Adjust threshold for earlier/later loading

 

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

});

 

How to Use It:

 

1. Replace “src” with “data-src” in your HTML:

<img data-src="image.jpg" class="lazy" alt="SEO alt text">

1. The script swaps “data-src” with “src” when the image is near the viewport.

 

Pros:

• Highly customizable (control loading thresholds, triggers).

• Works with any element (not just images).

• Better performance than scroll listeners.

Option B: Libraries like Lozad.js (Simple Setup)

If coding isn’t your strength, lightweight libraries like Lozad.js make lazy loading effortless.

 

How to Use Lozad.js

 

1. Install via CDN:

<script src="https://cdn.jsdelivr.net/npm/lozad/dist/lozad.min.js"></script>

1. Add lazy-loaded images:

<img data-src="image.jpg" class="lozad" alt="SEO alt text">

1. Initialize Lozad:

const observer = lozad(".lozad");

observer.observe();

Pros:

Dead simple setup (just add a class).
Supports videos, iframes, and backgrounds.
Tiny library (1KB gzipped). No performance hit.

4.3. WordPress Plugins

WordPress makes lazy loading easy with special plugins that do all the work for you. These tools help your site load faster without needing to write any code. They're perfect for beginners or anyone who wants a simple solution.

Top Plugin Choices

SiteGround Optimizer is one of the best plugins for speed. It automatically makes images and videos load only when needed. The plugin also shrinks image files and converts them to better formats. All you need to do is install it and turn on the lazy load option. It's very simple to use and helps your site score better in Google's speed tests.

 

Smush is another great choice that focuses on images. It does two important things at once - it makes images load only when visible and reduces their file size. The plugin is smart enough to skip lazy loading for important images at the top of your page. You can turn it on with just one click in the settings. This makes it ideal for websites with many photos.

 

WP Rocket is a paid plugin that offers more advanced features. It handles lazy loading for images, videos, and other embedded content. The plugin works well with its other speed tools to make pages load much faster. While it costs money, many users find it worth the price because it saves time and works automatically.

 

WordPress Best Practices

When using lazy loading in WordPress, remember some important tips.

 

• Always keep your logo and main banner images loading normally.

• Using lazy loading together with a caching plugin gives the best results.

• After setting it up, check your site with a speed test tool to make sure everything works right. 

 

Following these simple rules will help your site stay fast without any issues.

5. Best Practices for Lazy Loading

Lazy loading can significantly improve your website's performance, but only when implemented correctly. Follow these do’s and don’ts to ensure optimal results while avoiding common pitfalls.

1. Exclude Above-the-Fold Images

Images that appear immediately when the page loads (like hero banners or featured products) should never be lazy-loaded. These critical visual elements should load instantly (loading="eager") to provide a smooth user experience.

2. Set Width & Height Attributes

Always define exact dimensions for your images to prevent layout shifts (content jumping around as images load). This improves Core Web Vitals and user experience:

 

<img src="image.jpg" width="600" height="400" loading="lazy">

3. Use Blurred Placeholders

Low-quality image placeholders (LQIP) create a smoother loading experience. These tiny, blurred previews load instantly, then sharpen when the full image loads.

4. Implement Responsive Images

Use srcset to serve appropriately sized images for different devices, reducing unnecessary data usage:

 

<img src="small.jpg" srcset="medium.jpg 1000w, large.jpg 2000w" loading="lazy">

5. Test Across Devices & Browsers

Verify lazy loading works correctly on mobile devices and older browsers. Some may need polyfills for full support.

6. Never Lazy Load Critical Images

Logos, product images, and call-to-action buttons must load immediately. Delaying these can hurt conversions and user trust.

7. Don't Forget Alt Text

Empty alt attributes harm both SEO and accessibility. Always include descriptive text:

 

<img src="product.jpg" alt="Wireless Bluetooth headphones with noise cancellation" loading="lazy">

8. Avoid Lazy Loading Tiny Images

Small icons or decorative images under 5KB don't benefit from lazy loading - they should load normally.

9. Don't Overuse on Single-Page Apps

Excessive lazy loading in SPAs can cause performance issues. Implement strategic loading thresholds instead.

10. Never Skip Testing with Googlebot

Use Google Search Console's URL Inspection Tool to verify Google can properly index your lazy-loaded content.

 

Pro Tip: Monitor Performance

 

• Check LCP improvements in Google Analytics

• Track bounce rate changes after implementation

• Use WebPageTest for before/after comparisons

 

By following these best practices, you'll ensure lazy loading boosts speed without sacrificing user experience or SEO.

Conclusion

Lazy loading offers one of the easiest ways to significantly improve your website's performance and SEO rankings. By implementing this technique, you'll ensure images load only when visitors need to see them, resulting in faster page speeds and better user experiences.

 

The benefits are clear: reduced bounce rates, improved Core Web Vitals scores, and higher search engine visibility. Whether you choose the simple HTML method, JavaScript solutions, or WordPress plugins, lazy loading can be adapted to any website.

 

Remember to follow best practices like excluding critical images and always including alt text. These small optimizations can make a big difference in how both users and search engines perceive your site.