Definition
Lazy loading is an optimization technique that defers the loading of non-immediately-visible resources (images, iframes, videos) until the user scrolls to them. This reduces initial load time and bandwidth consumption. The native HTML attribute loading='lazy' is supported by modern browsers. Lazy loading is recommended by Google to improve Core Web Vitals, but it should not be applied to above-the-fold images to avoid degrading the LCP.
Key Points
- Reduces initial load time by deferring off-viewport resources
- Native HTML attribute: loading='lazy' (supported by modern browsers)
- Do not apply to above-the-fold images to avoid degrading LCP
Practical Examples
Images in a long article
A blog article with 30 images initially loads only the first 3 visible ones, saving 85% of bandwidth on the initial load.
Native HTML attribute
Adding loading='lazy' to img tags below the fold reduces the initial page weight from 4 MB to 800 KB.
Frequently Asked Questions
Google supports native lazy loading and recommends it. Ensure you use loading='lazy' or a Google crawl-compatible solution so images are properly indexed.
No, above-the-fold images must load immediately to avoid degrading LCP. Lazy loading is reserved for images further down the page.
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Last updated: 2026-02-07