Lazy Loading Images: Techniques

1. Introduction

Lazy loading is a design pattern that postpones loading of non-essential resources at the point the page is initially loaded. This technique can significantly improve the performance and loading times of websites that contain images, especially those that are large and numerous.

2. What is Lazy Loading?

Lazy loading defers the loading of images until they are needed. Instead of loading all images when the page loads, images are loaded as they come into the viewport. This is especially useful for long pages with many images, reducing initial load time and saving bandwidth.

3. Techniques for Lazy Loading

1. Native Lazy Loading:

   Modern browsers support a native lazy loading attribute for images. Simply add the loading="lazy" attribute to your <img> tags.

   <img src="image.jpg" loading="lazy" alt="Description of image">

2. JavaScript Intersection Observer:

   Use the Intersection Observer API to load images when they are near the viewport.

   
   const images = document.querySelectorAll('img[data-src]');
   const config = { rootMargin: '0px 0px 200px 0px', threshold: 0 };
   
   let observer = new IntersectionObserver((entries, self) => {
       entries.forEach(entry => {
           if (entry.isIntersecting) {
               const img = entry.target;
               img.src = img.dataset.src;
               img.onload = () => img.classList.add('loaded');
               self.unobserve(img);
           }
       });
   }, config);
   
   images.forEach(image => {
       observer.observe(image);
   });
                           

3. jQuery Lazy Load Plugin:

   If your project uses jQuery, consider using a lazy load plugin like jquery.lazyload.

4. Best Practices

• Use the loading="lazy" attribute whenever possible.
• Optimize images for web to reduce file sizes.
• Provide a low-resolution placeholder image for better user experience.
• Test across multiple devices and browsers for compatibility.

5. FAQ