What is Lazy Loading ? How it Helps to Increase Your Website Performance

Lazy loading refers to a web development technique that loads content on demand. The goal of lazy loading is to reduce the initial payload transferred over the network by delaying requests for content until it’s visible in the user’s viewport.

It can significantly help improve website performance and save bandwidth, which makes this a useful tool for developers looking to squeeze every last ounce of efficiency from their site’s codebase. However, there is a lot to learn more about lazy loading. Therefore we have covered everything about lazy loading in this post. Keep reading to find out more about the topic.

So, what exactly is Lazy Loading?

By loading content in a more intelligent manner, lazy loading can help give users a more seamless experience, especially on mobile devices.

It does this by loading only what is required for the current view of the website and nothing more. This cuts down on the number of objects being transferred over the network and, in turn, reduces cellular data usage and increases page load speed.

Lazy loading helps to fetch data only when it is visible on a page – which means you do not incur any cost until it is actually shown to the user.

For example, if you have images which are not visible in the current viewport and are supposed to be hidden, don’t fetch them.

What is Eager Loading?

Eager loading is the opposite of lazy loading, in which all the images are loaded with the initial HTML response. This means that when a web page is loaded, all the images will be loaded along with it, regardless of whether they are actually required or not. This can be done by just removing the “lazy load” class from image elements. Images lazy loading will then cease to be lazy loaded, and they will be loaded as soon as possible.

What is the Difference Between Eager Loading and Lazy Loading?

Both eager loading and lazy loading are used for images on web pages, but they work in opposite ways. Eager loading is similar to the initial image load, while lazy loading is similar to the later image load. Lazy loading improves the overall performance of web pages as it reduces page load time by deferring the execution of certain scripts.

It also allows you to load JavaScript only when it is required and not at the outset. This prevents your webpage from being indexed by search engines when unnecessary resources are loaded on the initial request.

How Lazy Loading Works?

Lazy loading is one of the most effective techniques in web performance optimization and is commonly used in almost all web projects. Lazy loading works by loading only the required resources for a particular viewport rather than loading all the content on the first visit.

As soon as a user scrolls down your webpage, another request is sent to load additional resources that are required to fill the browser’s viewport space. This reduces bandwidth usage by transmitting objects as they are needed instead of sending them all at once. This technique focuses on adding more segments of the webpage as the user scrolls down the screen.

The request for all the additional content is made just before the browser is requested to display that content. Along with this, Lazy loading also extends to cross-origin requests, which greatly improves page performance.

Why is Lazy Loading Important?

In a recent study by gomez.com it has been found that 57% of consumers abandon a website that takes longer than 3 seconds to load. We all know how internet speed is growing tremendously every year, and more users are accessing the internet on mobile devices.

Lazy loading for a website can be one of the most powerful tools to make your site’s performance better and faster. Moreover, this technique works consistently with responsive web design.

This means it will work even if you are building responsive websites. Lazy loading will allow you to load only what’s needed for the viewport at a given moment without slowing down other parts of the website.

In 2016, Google announced that they will recommend filtering images on domains containing ‘.jpg’ extension only, marking other image formats as a potential security risk. For sites with CSS-based lazy loaders (i.e., responsive websites), the browser will still need to download the full image data before displaying it, making them insecure and slow to load.

Advantages of Lazy Loading

It saves bandwidth as it only loads what is visible in the viewport, allowing data to be delivered in small chunks rather than one large payload.

As it only loads what is visible in the viewport, allowing data to be delivered in small chunks rather than one large payload. It helps reduce load times as it loads content once that content is needed by the user. Here are some more advantages of Lazy Loading:

1.  Accelerated initial loading: Lazy loading can significantly speed up the time it takes to load a page by only loading appropriate content when the page is first shown to the user.The content will only be loaded when it is needed, and it saves on bandwidth, which means that fewer data is transmitted over the network, increasing download speeds.
2. Less bandwidth consumption: As the user scrolls through the page, additional content will load in the background. This can be done using a combination of CSS and JavaScript.
3. Reduced CPU processing: Lazy loading ensures that only those resources needed are transferred from the server, resulting in a reduction of processor usage on both the client and server sides.
4. System resources being preserved: Lazy loading is an effective way of preventing the JavaScript execution stack from flooding and crashing the browser.
5. Improved user experience: Lazy loading ensures that resources are only loaded when they’re needed by a user. It takes time for data to load, which means that a user’s experience is not affected by unnecessary content.
6. Browser workload reduction: Lazy loading allows the browser to be more efficient in terms of managing its resources.
7. More data transfer efficiency: Lazy loading also works on mobile devices, which means that users are provided with a better experience when visiting your website, as content is loaded only when it’s needed by a user.
8. Reduced CPU usage: Since only parts of the web are being requested, there is less processing required by the browser when previewing content and, therefore, less strain on the processor for display data.
9. Reduced rendering time: When the browser requests data from a server, the amount of parsing can be reduced by only requesting the necessary data.
10. Content loading asynchronously: This technique allows for a page to be rendered before all of its dependent content is loaded. It also allows for a page to be progressively enhanced with additional features and functionality as resources are available for them.

These are some of the most significant benefits of using lazy loading, and there are many more. You can increase your site’s performance by improving its speed and efficiency.

What Drawbacks Might Lazy Loading Cause?

It can have a negative impact on the user experience if not implemented properly. This is due to the fact that content might take time to load as it is being fetched from the server – and it might be hard for users to comprehend which elements are loaded and which are not.

Here are some disadvantages of lazy loading that you may encounter:

1. Users may seek resources more quickly than anticipated: Users will tend to seek resources more quickly than expected, which can be a problem for users with slower connections. Lazy loading does this by loading only what is visible in the viewport, which means that as well as being accessible quicker, it is also more usable for the user.
2. No guarantee of completeness: Lazy loading relies on browser support and being able to load resources in order (for example, an image tag won’t work if there are other elements currently being loaded). If the browser does not support lazy loading, then all resources will be immediately loaded in their entirety. This can also cause problems if there are small elements which fall within a pre-loaded element. For example, if an element which is pre-loaded contains small elements (such as a header inside a header), lazy loading may not work.
3. Requires server configuration: Server configuration is required to enable lazy loading. In particular, all resources need to be requested from the server in the order in which they will be displayed on the page, and they need to be prefetched before being called by JavaScript.
4. Lazy loading creates a dependency on server resources: If the server does not have sufficient resources to pre-load all of the elements, then lazy loading will not work at all. Servers are often under pressure from other services and will only have time to provide partial resources when requested by a user.
5. Additional server communications: Server communication is used to indicate the start of lazy loading to the server. This may result in bandwidth overheads or latency issues as resources are transferred between the browser and the server.

How to Implement Lazy Loading on Your Website?

The first step is to decide where you want to implement lazy loading. This can be images, videos or any other part of your website. It should be made a decision only after analysing the requirements and choosing the best way to do it for your specific situation.

1. JavaScript implementation: Lazy loading can be implemented using JavaScript frameworks like jQuery, MomentJS or Scott Jehl’s Lazy Load Plugin.
2. CSS implementation: It can also be done using CSS techniques like media queries, viewport units or other similar techniques to overcome the asynchronous nature of lazy loading.
3. Server-side implementation: Some CMS platforms like Joomla and WordPress allow you to implement lazy loading on the server side. This will give you more control over it.

For example, Joomla allows you to add a custom component to the site, which you can use for lazy loading — in this case, the component was called ‘lazy-images’. All the images on the page are loaded when they are visible to users.

How can you Know Whether Lazy Loading is Working?

Websites that use lazy loading are fast to load. There are two ways of finding if the website is using lazy loading. One is by using a website speed checker or installing a Lazy Load plugin for your browser.

The other way you can determine lazy loading is by looking at a website’s network requests. If you observe that each request is preceded by an HTTP Link: header, then it means that both HTTP requests and responses are in sync. For example, the request is followed by an HTTP 200 response. This is a sign that lazy loading is being applied to the page.

https://pagespeed.web.dev/ and  https://gtmetrix.com/is one of the best website speed checkers that can test a website’s performance in real-time. It also shows how much time it takes for a page to load and renders that page as well.

Which Image Types Support Lazy Loading?

Usually, lazy loading is supported by many image types, such as GIF, JPEG, PNG and WEBP. It also works for videos. Generally, when you add an “src” attribute to the <img> tag, the browser will fetch additional resources only when an image is scrolled down.

Image Optimization with Lazy Loading :

1. Use of GIFs: Lazy loading is mostly used for images that have small dimensions (with no width or height specified). You can easily find out the dimension of your images lazy loading by using a tool such as tinypng.com. If your image has dimensions that need to be fixed, then GIFs (an image format with a high compression level) will help you too lazy load images. However, this also affects page render time and hence should be used with care.
2. Use of Responsive Images: Another way to use lazy loading is by adding “srcset” attribute to the <img> tag in HTML. With this attribute, you can specify a different set of resources that can be loaded to render the same image in different screen resolutions. This will force the browser to fetch images with a specific size when an image is scrolled down.

Lazy Loading’s Dependence on Javascript

There are certain ways to images lazy loading without the use of Javascript. However, it’s better to implement lazy loading using JavaScript since it prevents Javascript errors. This approach is also used by search engines (such as Google) and is recommended for SEO best practices.

But, you can also choose to only lazy load some images using CSS while lazy loading the rest of your image assets using JS and replace them with <noscript> tags when JavaScript is disabled.

Popular Libraries for Lazy Loading in Javascript on your Website

There are many libraries that can be used for images lazy loading. Generally, these libraries make use of the “lazyload” and “goto-image” CSS classes. Here is a list of some popular libraries:

1.  lazyload.js: this library uses JavaScript to lazy load images on scrolling down. It uses the “fully loaded” property provided by jQuery to determine whether the image is already loaded or not at the moment of scrolling down.
2. yall.js: This is an open-source javascript library that uses gesture events to lazy load images on scrolling down. It is generally used with a framework like jQuery.
3. lazysizes: This is an excellent library that can be used with jQuery. It uses the “is-lazyload” class to load images when it is scrolled down.
4. WeltPixel Lazy Loading Enhanced: This is a lightweight library that uses CSS media queries to load the images on scrolling down. It also supports image carousels and provides you with options to set up in the beginning.
5. Js Lazy Load: This is an easy-to-use library that images lazy loading by making use of the “lazyload” class attached to an image element. It supports all types of browsers, including IE9+.

Tools Used to Execute Lazy Loading

It is important that you choose an appropriate tool which will not only serve your purpose but can also deliver results as per your expectations. There are two types of tools which you can use:

1. Plugin / Extension: This will help you to implement lazy loading in your site, and there are many extensions available for popular frameworks like JQuery, AngularJS, React and Vue.js.
2. Libraries: Libraries like loadCSS, LazyLoad etc., can be used as per your needs to implement lazy loading in your site easily.

Lazy Loading In Angular 2+

Lazy loading is one of the features which are available in Angular 2+. It can be used to load only the part of the page that needs to be loaded when the user scrolls down. This reduces the time needed to load content and therefore improves the performance and speed of your website.

Lazy loading helps you avoid a number of issues related to asynchronous operations like downloading, parsing and transferring data between server and client.

The Effect of Lazy Loading on SEO

Lazy loading can affect SEO in a number of ways. For example, if your company has a large number of images on the homepage, then it will take longer for your webpage to load. These images are optional for the page to be rendered, and hence lazy loading will prevent them from being loaded initially. This reduces page rendering time, which improves overall performance and also scores better on mobile devices.

Lazy loading, on the other hand, can have a negative impact on SEO. If all the images are lazy loaded, then it will take longer for the page to load as the HTML document has to be loaded along with all the images. This will also prevent your page from being indexed by search engines and, in general, will impact SEO negatively.

However, these drawbacks can be overcome. You can add a rel=” alternate” link to all the images that you decide to lazy load. This will tell the search engine crawler that the main image has already been loaded but is just not being rendered at the moment. It will then ignore these lazy loaded images and index them.

The images are still available to be lazy-loaded when needed by the user, but they will no longer be indexed by search engines when not being used by the user. This can also be applied to the content of the page. For example, if you are lazy loading the content of a post and the rel=” alternate” link is added to it. This will allow search engines to index the content without affecting user experience.

Some the Examples of Lazy Loading

Let’s take a look at some of the examples of lazy loading used in real-world web applications.

1. Direct Lazy Loads

DLL (Dynamic Link Library) is a feature of AJAX that is used to populate an HTML document with images and other content. The feature can be used to load only the required CSS file, JavaScript file, or content of a particular document. This allows you to pre-load resources that are not needed on the first visit and will help improve the overall performance of your website. It’s also a good SEO technique when implemented consistently on all pages.

2. Horizontal Scrolling

This technique was first used in Google’s mobile-optimized site. When there is a long document to load, AJAX sends the request for resources to load content as the user scrolls down the page. This technique extends to cross-origin requests, which greatly improves page performance. This allows you to send only one request to load a particular resource instead of sending multiple requests for that resource.

3. Content Deferment

This is an important SEO technique that helps to improve the performance of the page by loading JavaScript only when it’s needed. This greatly reduces the load on a server and also improves user experience by loading content only when required. The technique works well with progressive enhancement since it allows you to add functionality incrementally to your site rather than fully loading all the content at once. This technique can be implemented in any framework or CMS and will allow for a better user experience.

What are some Additional Approaches Similar to Lazy Loading?

There are many other techniques similar to Lazy Loading. These include:

1. Using CDN: A CDN (Content Delivery Network) is a collection of servers that constantly provides a website with content. This helps to improve the overall performance of a website by bringing the content closer to the user, thereby reducing the latency and increasing the speed at which content is delivered.
2. Content Deferment: Also known as “Asynchronous Javascript”, CJD (Content Deferment) is another technique similar to lazy loading that loads JavaScript before the page render completes but after the HTML document has been fully loaded.
3. Fixing images: Images are one of the biggest reasons for any page’s high loading time. As a result, images shouldn’t be loaded with the page content. Instead, they should be loaded independently when the user scrolls down the page. This prevents unnecessary load on a web server and also reduces the overall loading time of a webpage.
4. Removing unused CSS: This is an important SEO technique that helps to improve performance significantly. Removing unused CSS will keep your website’s rendering time to a minimum, and your website will also rank higher.
5. Deferring JavaScript execution: This is one of the most important techniques used to improve the overall performance of a webpage. JS is not loaded with the site’s initial HTML load but rather loaded after everything else has been displayed on the page. This technique allows you to load JS only when it’s needed instead of loading everything at once later when it may not be required anymore.

How to do WooCommerce Lazy Load?

WooCommerce is one of the most popular eCommerce platforms on the internet. More than 60 thousand merchants are using it to sell their products online. It is a full-featured eCommerce platform and allows you to sell your products from a single website. It also has a plugin that can be used for lazy loading WooCommerce images. You can install the plugin to implement this technique.

Conclusion

The lazy loading technique is one of the most promising techniques to speed up your website. For a large number of websites, minimising the number of requests to a server will result in a significant increase in performance for both desktop and mobile devices.

If you are using WordPress or Joomla, you have many options available to achieve this. But if you’re using a different platform like Laravel, NodeJS or Go, then consider using third-party libraries to implement it.

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