Review image loading settings based on where images appear on a page. Identify offscreen images that should load later, keep important visible images loading promptly, and add image dimensions to reduce layout shifts.
Use when reviewing image assets, markup, and CDN or build transforms related to Lazy load offscreen images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together. Missing `loading='lazy'` is only a valid finding when you can reasonably tell the image is offscreen or non-critical.
offscreen-lazy checks page images and adjusts loading settings to match their position. It adds loading="lazy" to images outside the initial viewport and removes it from important images visible immediately, such as hero images. For the LCP image—the image used to measure when the main content appears—it sets fetchpriority="high". It also checks width and height on lazy-loaded images. The output includes corrected HTML for each changed image and instructions for checking it in DevTools.
Use it on pages with many images to investigate unnecessary downloads during the initial load. It also helps when reviewing image data size, displayed dimensions, and loading order together.
If an image’s position cannot be determined from a code snippet, missing loading="lazy" alone is not treated as a defect. Important images visible initially and offscreen images are reported separately. The source specifies native lazy loading in current major browsers, without a JavaScript polyfill.
This overview was written by AI (OpenAI Codex) from the public SKILL.md. Check the original below for the exact behavior.
AI rated this skill on four points using only the contents of its SKILL.md. Stars and popularity are not taken into account.
The total counts each point as A = 25, B = 15, C = 5. Rated by AI (OpenAI Codex) as of Oct 23, 2026. Treat it as a guide and read the original before installing.
Review the instructions the agent will receive before you install.
Lazy loading eliminates unnecessary image downloads on initial page load. A page with 20 images below the fold may transfer several megabytes of data that users who don't scroll will never see. Deferring these downloads reduces Time to Interactive, improves LCP for above-fold content, and saves bandwidth—particularly impactful for users on metered mobile connections.
loading="lazy" to all <img> elements below the foldfetchpriority="high" insteadloading="lazy" with width and height attributes to prevent CLSloading="lazy" has universal support in all modern browsers—no JavaScript polyfill neededScan all <img> elements in this codebase. Identify: 1) Any <img> elements below the fold (not in the first viewport) that are missing loading="lazy". 2) Any <img> elements marked loading="lazy" that appear to be above the fold (hero images, first product images, logos in headers). 3) Any <img> with loading="eager" below the fold. Report the above-fold images that should NOT have lazy loading separately from below-fold images that should have it. If fold position cannot be inferred from the snippet, do not report missing lazy loading as a defect.
For images that should use lazy loading: 1) Add loading="lazy" to all <img> elements that appear below the fold. 2) Remove loading="lazy" from any hero, logo, or first-visible image—these should load immediately. 3) Ensure all lazy-loaded images have explicit width and height attributes to prevent CLS. 4) For the LCP image specifically, add fetchpriority="high" and remove loading="lazy". Show the corrected HTML for each modified image.
Explain how native browser lazy loading works. The loading="lazy" attribute tells the browser to defer image download until the image is within a browser-defined distance from the viewport (typically 1250px on a slow connection). This reduces the data transferred on initial load, lowers Time to Interactive, and saves bandwidth for users who never scroll to those images. Browser support is universal in modern browsers. The critical caveat: never lazy-load the LCP image—it must load as fast as possible.
Review image assets, markup, and delivery configuration related to Lazy load offscreen images. Flag exact files or components where format choice, sizing, or loading behavior violates the rule, and describe how to confirm the fix in DevTools.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/images/offscreen-lazy
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