Images are essential for any website, but they can also slow down the page loading speed and affect the user experience. That's why many web developers use a technique called lazy loading images, which means loading images only when they are needed, not all at once.
Lazy loading images can improve the website performance, reduce the bandwidth consumption, and save the device's resources. It can also enhance the user engagement, as users don't have to wait for a long time to see the content they are interested in.
Lazy Loading Images Infographic
To help you understand better how lazy loading images works and why it is beneficial, we have created an infographic that shows the difference of page with and without lazy loading. You can see it below:
This infographic is available on CC BY 4.0, which stands for Creative Commons Attribution 4.0. This means that you are free to share, copy, distribute and transmit the work, as long as you give appropriate credit. Link back to this page.
How to Implement Lazy Loading
There are different ways to implement lazy loading images on a website, depending on the type of images and the browser support. Here are some of the most common methods:
Using browser-level lazy loading: This is a native feature supported by some
modern browsers, such as Chrome and Firefox. It allows you to add a
<iframe>elements, which tells the browser to load them only when they are in or near the viewport. This is the simplest and most efficient way to lazy load images, but it may not work on older browsers or devices.
monitor the visibility of an element on the page. You can use it to check if
an image is in the viewport, and then load it dynamically by changing its
srcsetattribute. This method is more compatible across browsers than the native lazy loading, but it requires some coding skills and polyfills for older browsers.
using event handlers such as
resize. You can use them to detect when an image is close to the viewport, and then load it by changing its
srcsetattribute. This method works on most browsers, but it can be less performant and efficient than the other methods, as it may cause unnecessary reflows and repaints on the page.
Using CSS background images: This is a way of lazy loading images that are
set as the background of an HTML element, such as a
background-imageproperty of the element based on its visibility or screen size. This method can be useful for responsive design, but it may not work well for images that need to be accessible or SEO-friendly.