Ultimate Guide To Lazy Load Images For Website Performance

Nov 2018 / helena

Ultimate Guide To Lazy Load Images For Website Performance

Now a days it has become a trend to use informative and attractive images in websites to be more popular and user friendly. This helps the end users to understand what they are looking for by viewing the images rather than reading informative paragraphs.

Due to this trend the performance of the website is highly affected as the images used in the website starts loading all together when a particular page is being viewed by the user. This process works as an catalyst for the poor performance of the website in terms of loading time. Users have to wait for long time until the images are properly loaded. This results in users getting diverted to other websites as they have to wait for longer time to view the content. To avoid such situation Lazy Loading Images is the best solution.

Lazy Loading Images

The Lazy Loading Images is an unique technique to improve website’s performance. It is smart enough to load only those images which are on browser’s viewport and not all at once. This helps in reducing the loading time of website and when user scrolls to view more images, at that point of time the next images will load for display else it will not. This technique not only helps in reducing the image loading time but also it helps in reducing the bandwidth used for loading the website. This helps the vendors in retaining their users as they don’t have to have for long time to view the website content.

Most popular approaches for Lazy Loading Images:

1. Lazy (jQuery):

This library needs to be included along with jQuery library. This technique depends on jQuery, It makes the process simple to implement and is very helpful to implement Lazy Loading Images on our website.

Let us consider an simple example of this:

Lazy image loading 1

In the above code we have included Lazy and jQuery library in our page. We also set the placeholder ‘image assets/img_placeholder’ . Then we have assigned the data-original attribute with the URL of original image.

Now we need to write following in to our code:

Lazy image loading 2

The above code will Lazy Load all the images with the class ‘lazy’.

2. Echo.js:

This is a very compact javascript library and very simple to implement. It does not require any other library like jQuery. It has an straightforward approach to implement Lazy Load Images.

Let us consider an simple example of this:

Lazy image loading 3

That’s it, just echo.init() will handle all the lazy loading functionality. We can also use the callback functionality for images that is lazy loaded.

3. Lazy Loading by Blurred Effect:

Now a days it is common for websites to load low resolution blurred image first while the actual high resolution image is been loaded afterwards.

This is also a Lazy Loading techniques to retain users while the actual images are been loaded. This techniques uses only css and javascript to achieve Lazy Loading. We do not require any external library such as jQuery, etc. This is one of the simple approach to achieve Lazy Loading Images on our website.

4. Yall.js:

This is a very powerful way to implement Lazy Loading. It offers not only Lazy Loading Images but also supports Lazy Loading of Videos and iframes, which is a great functionality when required and comes very handy. Yall.js works on Intersection Observer API and Event handlers.

To initialize Yall see the script mentioned below:

Lazy image loading 4

5. Lazysizes:

Lazysizes, the lazy loader for images are high in performance and SEO Friendly. It is very useful for both (responsive and normal), iframes and more.
Lazysizes automatically detects any visibility changes which are triggered through user interaction, CSS or JavaScript. It does this without any need of configuration and is very easy to use. Lazysizes is very extendable, it provides JS and CSS hooks that easily extend lazysizes with any kind of lazy loading, lazy instantiation, in view callbacks or effects.

Lazy image loading 5

Just add the class lazyload to all img and iframe elements, which should be loaded lazy. So Instead of a src or srcset attribute we need to use a data-src or data-srcset attribute. Lazysizes supports setting the sizes attribute automatically. According to the current size of your image – just set the value of data-sizes to auto.

Lazy image loading 6

You can also use the LQIP (Low Quality Image Placeholder) pattern, for this simply add a low quality image as the src. It offers lots of features you can get it from its GitHub repository.


The lazy loading is an excellent concept and improves the website performance and more importantly the user experience. This is very helpful to the users having low speed internet connection.
It helps user save their network bandwidth and data usage because only those lazy loading elements which are in viewport will be loaded and not all of them at once.

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