Lazy loading, or on-demand loading, is an optimization strategy for online content, encompassing websites and web applications. This technique deviates from the conventional approach of loading an entire web page and promptly displaying it to users. Instead, lazy loading focuses on loading only the pertinent section, deferring the remaining content until the user necessitates its display.

One manifestation of the technique is the concept of infinite scrolling. In this method, webpage content is progressively loaded as the user scrolls downward. This technique enjoys popularity across diverse websites to optimize content delivery.


  • Time and Memory Efficiency. On-demand loading reduces time consumption and memory usage, optimizing content delivery. The loading time is minimized by loading only the essential portion of the webpage initially. Subsequent sections are loaded with a delay, conserving storage space. This rapid delivery of requested content significantly enhances the user experience.
  • Elimination of Unnecessary Code Execution. Lazy loading prevents the execution of unnecessary code, enhancing overall performance.
  • Resource Optimization. This approach effectively utilizes time and space resources, making it a cost-effective solution from a business perspective, especially for website owners.


  • Increased Code Complexity. Implementing lazy loading requires adding extra lines of code to the existing ones, potentially complicating the codebase.
  • Potential SEO Impact. Lazy loading might adversely affect a website’s search engine ranking due to improper indexing of unloaded content. This can lead to reduced visibility in search results.

Implementing Lazy Loading for Images

One approach to implementing the technique involves utilizing the HTML attribute “loading” within an image tag. By including loading=”lazy” as demonstrated in the following example, the browser is instructed to postpone image loading until the user scrolls in proximity to it:

<img src="" alt="example image" width="100" height="100" loading="lazy">

Web developers also have the option to leverage programming frameworks for more advanced lazy loading functionalities. Angular is a commonly employed framework for this purpose. Additionally, the JavaScript library React provides support for implementing the techniques.

Other Page Resources Suitable for the Technique

  • JavaScript, a resource that often causes rendering delays, can be optimized through lazy loading. Dividing JavaScript code into smaller modules and loading them as needed minimizes page load times, especially for pages reliant on JavaScript execution.
  • CSS, another render-blocking resource, can benefit from the technique. Breaking a CSS file into multiple parts that load selectively reduces the duration a browser is hindered from rendering content. Non-blocking CSS files should possess separate links, accompanied by a media property indicating when they should be loaded.
  • iframes serve to embed external content within a webpage. The same HTML loading attribute mentioned earlier for images can be applied to iframe tags. This approach delays iframes loading until they approach the visible portion, optimizing resource utilization.


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Alex Osmichenko
Business Consultant
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