Definition
Lazy loading changes the browser's resource priority. Adding <img loading="lazy"> makes the image download as it approaches the viewport. A custom implementation can also use the IntersectionObserver API.
How it works
While loading, the browser skips resources with loading="lazy". As the user scrolls, resources nearing the viewport start downloading. The LCP image should not be lazy; otherwise LCP time stretches. A fallback is needed in browsers without native lazy support.
Where you see it in Scope Trends
Crawl Report > Image SEO tab shows lazy vs eager loaded resource counts. If a marked LCP Candidate image is lazy, a warning fires.
Frequently asked questions
Should I lazy-load the LCP image?
No. Always eager-load the LCP candidate and add fetchpriority="high".
Does lazy loading hurt SEO?
Done right, no. A wrong implementation (e.g., JS-only late render) can block indexing.