What Is Lazy Loading And Why Should You Be Interested In It In The Context Of SEO? - Semalt Expert

47% of Internet users expect the page to load within 2 seconds. What happens in the event of a longer charge? The user will not read the content on the site, nor will the transaction be made. He will go away and may not come back. So there is no question of high conversion.

The website owner only has a few seconds to first interest and then keep the user on the site. If, after entering the website, the user encounters any complications, e.g. incorrect data scheduling, poorly designed website architecture, or a page loading error, he will choose another place on the network and probably will not come back.  That is why solving the problem of slow page loading, as well as a clear and intuitive interface, are important issues in SEO optimization. Did you know that, according to Google's data, a page that takes more than 5 seconds to load may experience up to a 40% decrease in conversion? Reason enough to shift up a gear.

What is lazy loading?

Although the very concept of lazy loading should in fact be understood as slow loading, from the perspective of SEO solutions, it has completely different connotations. In fact, it is nothing more than a script inserted into the page code that controls the loading of media (images and videos) placed in the page code. Thanks to it, multimedia is loaded only when the user goes to a specific section, and not immediately after going to the target web address. This scheme of operation speeds up the loading process of the website and encourages you to use it, although the name of the script itself can be quite misleading.

It is worth mentioning that one of the ways to speed up the loading of a website is the asynchronous loading of JavaScript scripts. Knowing about this method is especially important if the scripts are on remote servers. It takes a long time to replace such files. The script itself can also stop the processing of the rest of the elements. In this case, you have to force the browser to asynchronously load.

The results will be important from the point of view of the website owner. And these are very easy to read as your website loading time should be significantly shortened. It is enough to imagine the very process of the website operation.

If we are dealing with an extensive website with a large amount of content, loading all multimedia files at the same time would be a total burning of its resources.

When the lazy loading script is implemented, data sequences relevant to explaining a specific problem or topic that are currently being considered on the site are run. For the user, the data is delivered immediately, and at the same time he has no awareness and does not bear any consequences that the remaining graphics wait for their loading time - this will only happen when he becomes interested in them while scrolling the page.

Why is the lazy loading script a good solution for your website?

If you actually analyze who visits your website (you can use this tool: the Dedicated SEO Dashboard) and how they behave on it, you know that the user does not always spend a lot of time on it and does not delve into the structure of links and subpages to carefully look at the offer or products (which is a pity). Usually, he/she goes straight to the landing page (certainly with AdWords campaigns), reaches for information, fulfills his/her need, and moves on. Therefore, it makes no sense for them to load all other graphics unrelated to the purpose of his visit during this short presence.


Jack is looking for a motorbike. He had always dreamed of it but had never been able to afford the expense before. Finally, he raised 20,000 $ and is ready to choose the dream model. Therefore, he enters in the search engine "good motorbikes up to 20 thousand $".

Appear to him:
  • Multi-search engines with sales offers - sorts models in them according to selected parameters. He opens tab by tab and browses the offers.
  • Content websites - guides for buying and choosing a motorbike.
While Jack spends a lot of time on the classified website, because he has to select the perfect vehicle, on the content site he will probably not spend more than 8-10 minutes on one page of the article and move on.

The important thing in this example is that it is not necessary to load all photos from a given subpage of the content website for Jack - the graphic design of the article is enough. You do not have to provide him with photos of all available models in the multi-search engine. After all, he will only be tempted by a few!

Such a scheme of operation, called loading images on demand, is the best solution for maintaining the comfort of using the website and the speed of using it. You will gain time and receive higher marks for the quality of the website.

Lazy loading of unnecessary resources is an absolute "must-have" for any website that wants to serve its content to users in a short time. It is worth remembering that since July 2018, website speed is officially one of the ranking factors when determining the position of mobile search results on Google, so when optimizing the website for SEO, you should pay attention to this aspect.

What can you change in the website loading process? What does Google say?

Website loading speed is not only an element that inspires customer satisfaction. It is also one of the ranking factors positively influencing the evaluation of the positioned website. Before the user sees it, the browser has to take a few steps on it. If something goes wrong at any of the analysis stages, the user will have to wait a long time for the site to load.

Your website consists of resources such as HTML code, CSS code, and JS code, which are responsible for graphic elements. For the user to get a ready view, the browser needs to read each view. A view with a lot of content will therefore require a longer loading time for the website and scrolling of the entire subpage. This is not the best solution for you and the user. The user loses his transfer on the phone or overloads the home connection with unnecessarily loaded resources. As a website owner, you also suffer from this when you use a server that has limited bandwidth or you lease resources depending on the amount of traffic on the site.

Let's be clear - most of the factors influencing the website loading speed can be touched by you and you can speed up this process with specific actions. As the owner of the website or the person responsible for its optimization, check the hosting server. It should have the capacity to match the size of the site and the volume of traffic on it. This is the basis that needs to be taken care of when developing a website.

You can spend a lot of money optimizing and spending a lot of time implementing it, but if the server is slow, the website won't speed up. So don't go for the first better hosting provider!

Already in 2009, Amazon showed that every 0.1 sec. delays in the performance of their website cause a 1% drop in sales. This means that every second of delay costs Amazon "only" 10% of revenues!

How to implement a lazy loading script?

The implementation of the lazy loading script involves making some changes to the website code. To do this, you can use ready-made CMS plugins or JS plugins.

In the lazy loading script, you should not include the images at the top of the page and all "hero images" logos. If you implement lazy loading for graphics that were placed at the top of the page, instead of showing them to the user immediately, the script will additionally analyze the process, which of course will lead to delays and a significant reduction in UX quality. The effect of such optimization will be counterproductive.

Incompetent implementation of lazy loading may result in the user not seeing graphics in the initial stage of rendering the page, and the website content will be displayed incorrectly.

How is the script implemented in the code?

Be aware that embedded iframes also use a lot of data and can degrade page performance. Therefore, it is worth making sure that they are loaded only when the user needs them. This shortens the overall page load time, but also minimizes user bandwidth and reduces memory consumption.

Unfortunately, search engine bots prefer pages whose HTML code can be crawled quickly. Googlebot can render JS based on Chrome41, but does not always index correctly in this situation. Put simply, robots may not notice these pictures.

Useful tips

If you notice problems with loading the website, then:
  • use Gzip compression, which is a method of compressing HTML and CSS files on the server side. Its use saves from 40 to even 80% of the original file size;
  • verify and update the database, which grows during updates and implementations;
  • take care of browser caching; the server will not have to send all the elements of the website every time the user visits it, because some of them will be cached;
  • get rid of all unnecessary scripts and plugins that do not affect the proper functioning of the website.

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