How Lazy Loading Images Can Improve Web Performance

As a website owner, you’re always looking at ways to improve your website’s performance. Lazy loading is a technique used to decrease page load times. When you visit a website without lazy loading, it tries to load all its content at once, including images. This can make the site slow, especially if it has a lot of images. Lazy loading changes this by only loading images when you need to see them. Instead, it puts lightweight placeholder images in place until the user scrolls down. The images won’t load until they come into the full viewport.

How To Improve User Experience With Lazy Loading

Using lazy loading enhances user experience in a few ways. The most valuable is that it speeds up page load times. When a website only loads images in view, it reduces the data the browser needs to process right away. This means users can start using the site sooner and won’t have to wait for it to load all at once. If you want to see an example of this in action, check out our resources page.

Lazy loading can also save on data. For users on limited data plans or with low bandwidth, loading only necessary images can cut data use a lot. This is especially important for mobile users who often rely on data connections.

Last but not least, it improves website engagement. Faster loading times and efficient data use make users more likely to stay on a website longer. Fast websites make users happy. This leads to better engagement and more conversions in the long run. 

Lazy Loading = Better SEO

The lazy loading of images can also lead to better SEO (Search Engine Optimisation). Search engines like Google use page loading speed as a ranking factor. Faster websites rank higher, making them more visible to people searching online.

Lazy loading also reduces bounce rates. A bounce happens when someone leaves a website not longing after landing on it. One of the most common causes of this is frustration from slow page load times. If your website loads fast and keeps users engaged, they’re less likely to leave straight away.

It’s important to note that Bounce rate isn’t a confirmed ranking factor. But, a fast website makes visitors stay longer and explore more pages. This tells Google that your website has valuable content and a good user experience. And Google definitely cares about that.

Mobile loading speed, on the other hand, is a confirmed ranking factor. Lazy loading is great for mobile users, so it can definitely help boost your search ranking.

How To Implement Lazy Loading

You can implement lazy loading in a few different ways, depending on what you need for your website. Here are the main methods:

  • Browser-Built-In Lazy Loading: Known as native lazy loading, this is the simplest way to start lazy loading. Many modern web browsers support it right out of the box. All you need to do is add loading=”lazy” to your image or iframe code. This tells the browser to wait to load the image until it’s about to come into view. This method is great because it’s easy to use and doesn’t need any extra tools or scripts.
  • JavaScript Libraries: This can offer more control over lazy loading. They go beyond what the browser offers. These are bits of code that give you more flexibility with lazy loading. For example, you can decide when an image starts loading. You do this based on how close it is to being visible on the screen. Popular libraries include Lozad.js and LazySizes. They’re a bit more complex to set up but can handle more complicated needs.
  • Custom JavaScript: If you want to integrate lazy loading in a more tailored way, this is the answer. Custom JavaScript means you or your developer will write the code from scratch. It will control how and when images load. This method is the most flexible. But, it needs JavaScript knowledge and takes more time to set up.
  • CSS Tricks: CSS scripts aren’t a standalone method for lazy loading images. But you can use it with JavaScript to enhance the effect. It can also control the display of images before they load.
  • WordPress Plugins: If you use WordPress, implementing lazy loading can be even simpler. Plugins can automatically apply lazy loading to your images. This means there’s no need to edit code. Plugins like ‘a3 Lazy Load’ and ‘Lazy Load by WP Rocket’ are popular choices. They offer easy installation and setup directly from your WordPress dashboard. Just install the plugin, activate it, and configure the settings according to your needs.

Are There Any Downsides To Lazy Loading Images?

Lazy loading is something that we implement all the time, but like any technique, it isn’t perfect and might not suit every situation. Here are a few downsides to keep in mind:

  • SEO Implications: If not implemented right, lazy loading can hide content from search engines. Search engine bots might not scroll your page, meaning they don’t see or index the images when lazy loading is on. This is less of a problem now, as search engines have become smarter at recognising and indexing lazy-loaded content.
  • User Experience: If your lazy loading is too slow or not fine-tuned, it can lead to a poor user experience. Visitors might see blank spaces where images should be. They might also have delays in loading content as they scroll. This can be frustrating and may deter people from using your site.
  • Complexity: Adding lazy loading can make your website’s code more complex. This is especially true if you use custom JavaScript or libraries. If not done right, it might make your website harder to maintain and introduce bugs.
  • Overhead: Adding JavaScript libraries adds more code that browsers have to load. If not managed well, this could cancel the benefits of lazy loading. It would do so by making your web pages larger.
  • Incompatibility: Most modern browsers support lazy loading. But some older versions and certain browsers still don’t. This could lead to inconsistent experiences across different devices and browsers. It has potential downsides, but lazy loading is great when implemented with care. Consider your specific needs. Test your method well to be sure it helps users, not hurts them.

It has potential downsides, but lazy loading is great when implemented with care. Consider your specific needs. Test your method well to be sure it helps users, not hurts them.

Other Ways To Improve Load Times

Lazy loading is a popular choice to speed upwebsites but there are other strategies that can optimise loading times. Here are a few:

  • Image Compression: Before your images even get to the web, you can make them smaller in size by compressing them. This means they take less time to load. There are many tools online that can do this without losing the quality of your images.
  • Image Formats: Choosing the right format for your images can also speed up loading times. PNGs have the fastest loading times, but JPEGs preserve the most detail.
  • Use a CDN (Content Delivery Network): A CDN stores copies of your site’s content on servers around the world. When someone visits your site, the CDN delivers the content from the closest server. This can speed up loading times because the data doesn’t have to travel as far.
  • Prioritising Content: Decide what needs to load first on your website. Make sure essential content loads fast, and defer loading non-critical elements.
  • Effective Use of Caching: When someone visits your website, you can save some of its data on their device. Next time they visit, your site can load faster because it remembers some of its content. This technique can greatly speed up loading for return visitors.

Lazy Loading vs Eager Loading

Eager Loading is the opposite of lazy loading. It means a website loads everything right when you open the page. Every picture and video is ready to view immediately.

We know that lazy loading makes websites faster to start and saves data. Eager loading might not seem as good, but it still has its uses. It makes sure everything on a website is ready to see from the start. This could be useful for smaller websites where you need to see everything right away.

The choice between lazy loading and eager loading depends on your website’s complexity and image count. If you have no issues with page load time leaving your site as is, lazy loading might not be as worthwile.


Like everything, lazy loading has its pros and cons. But ultimately, we recommend implementing it on all websites. Users today have very little patience for slow loading times. Quick load times are key to a good user experience, and they can greatly affect how long visitors stay on your site. Anything you can do to improve your page speed should be done.

There are different ways to do lazy loading and other options to consider. But the speed, ease and efficiency of lazy loading make it well worth trying. It’s a proven, straightforward solution to slow load times.  If you want to learn more about website speed and why it’s so important, read our article on Testing And Improving Website Load Times.

  • Juliette Owen-Jones
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