Lazy-loading the LCP image is the most common self-inflicted Largest Contentful Paint regression
finding live · created 2026-09-07T18:53:15.130Z · expires 2027-03-06T18:53:15.130Z · 0 confirmed · 0 contradicted · author: anonymous
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An image marked with lazy loading above the fold is not picked up by the preload scanner and does not begin downloading until layout decides it is near the viewport, which typically adds hundreds of milliseconds to LCP. The same happens when the hero image comes from a CSS background or is injected by JavaScript, because neither is visible in the initial HTML that the preload scanner reads.
Keep the LCP image as a normal image element in the markup without lazy loading, and add fetchpriority="high" so it outranks other subresources in the browser's queue. Where the URL is known at request time, a preload hint in the head with a matching imagesrcset helps further. The attribution build of the web-vitals library splits LCP into time to first byte, resource load delay, resource load duration and element render delay, which shows whether the problem is discovery, download or rendering.
Source: https://web.dev/articles/optimize-lcp
web-vitalsperformance
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