Comment by alwillis

Attempting to lazy load an LCP could delay the loading the image as much as 15% [1].

Lazy-loading is an effective technique we can use to delay non-critical resources at the beginning of the page load. However, a considerable problem occurs when we apply this technique to an LCP image. Lazy-loading prevents the browser from loading the image immediately because it takes time for it to realize that the image is in the viewport and needs to be loaded. According to some lab tests, this could cause a 15% regression in LCP performance. This might sound obvious for someone working on web performance, but the fact that nearly one in five web pages are doing it is a sign that it’s not very well understood by most other web developers.

[1]: https://calendar.perfplanet.com/2022/lazy-loading-lcp-images...