Lazy loading is a performance technique where images, videos, or other resources are only fetched when they are about to enter the user’s viewport, rather than all at once when the page first loads. This reduces initial page weight and speeds up perceived load times. For SEO, lazy loading requires careful implementation: images that are deferred must still be discoverable by Googlebot. The loading="lazy" HTML attribute is the recommended approach; older JavaScript-based solutions can prevent images from being indexed if the crawler does not execute the script. Incorrectly lazy-loaded content can harm Largest Contentful Paint scores and reduce image indexation, directly affecting Core Web Vitals.