What Impact Does Using WebP Images Have on Core Web Vitals Scores, Particularly the Largest Contentful Paint (LCP)?


Using WebP images can significantly improve Core Web Vitals scores, particularly the Largest Contentful Paint (LCP) metric. The efficiency of WebP in terms of size and load speed directly contributes to faster render times for the largest content element on a webpage, enhancing user experience and potentially boosting SEO rankings.

What is Largest Contentful Paint (LCP)?

Largest Contentful Paint (LCP) measures the time it takes for the largest content element visible within the viewport to load. This metric is crucial as it directly impacts how quickly users perceive a page's main content to become visible. A good LCP score means faster perceived load times, enhancing user satisfaction.

Advantages of WebP in Optimizing LCP

Smaller File Sizes

WebP images typically have smaller file sizes compared to other formats like JPEG and PNG, without compromising quality. Smaller file sizes mean faster loading times, directly positively impacting LCP scores [WebP Compression, 2023].

Improved Load Times

By reducing the image load times, WebP helps browsers render the largest content element quicker. This is crucial for improving LCP, as images often constitute a significant portion of the Largest Contentful Paint [Largest Contentful Paint, 2023].

Integrating WebP for Better LCP

Responsive Images

Using the <picture> element along with WebP ensures that the browser loads the optimal image size for the device, further reducing load times and improving LCP. Example:

  <source srcset="example.webp" type="image/webp">
  <img src="example.jpg" alt="Example">

This method ensures backwards compatibility with browsers that do not support WebP [Responsive Images, 2022].

Preloading Key Images

Using the <link rel="preload"> directive for key WebP images can ensure that they begin loading as soon as possible. By preloading images that are crucial to LCP, you can improve the time it takes for these images to be displayed. Example:

<link rel="preload" href="example.webp" as="image">

[Resource Priorities, 2023].

Case Studies and Real-World Impact

Several case studies have shown measurable improvements in LCP scores after implementing WebP. For instance, Smashing Magazine observed a significant reduction in page load times by transitioning from JPEG to WebP images [Smashing Magazine, 2015].


The use of WebP images presents a substantial opportunity to enhance LCP scores, one of the critical Core Web Vitals metrics. By leveraging smaller file sizes, faster load times, and techniques such as responsive images and preloading, you can achieve a better user experience and possibly see an uptick in SEO performance.