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Lazy Load Checker Tool

Test whether a webpage uses lazy loading correctly, review image and iframe loading signals, spot hero image and LCP risks, detect missing dimensions that can lead to CLS, and get practical recommendations for better SEO and Core Web Vitals.

Image Lazy Loading Check Iframe Loading Review LCP & CLS Signals SEO-Friendly Suggestions

Analyze a Website

Enter a domain, with or without http/https. Press Enter or click Check.

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Run a check to see lazy loading signals, image handling issues, and improvement recommendations.

Performance Summary

Images Found 0 Total image tags found in HTML
Lazy Images 0 Images using loading="lazy"
Iframes Found 0 Total iframe tags found
Dimension Issues 0 Images missing width or height
Response Time — Time to fetch page source
Missing Alt Text 0 Images without alt attribute
No report generated yet.

Lazy Load Signals

Main technical checks related to lazy loading, LCP, CLS, and SEO readiness.

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Findings

What the checker found in the page source.

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No findings yet

Run a check to view detections and warnings.

Recommended Fixes

Action steps to improve performance and search friendliness.

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Run a test first

Once a site is checked, this area will list the most important improvements first.

SEO Impact

Correct lazy loading can improve perceived speed and reduce initial page weight. Incorrect lazy loading can delay important content and weaken page experience signals.

Core Web Vitals Impact

Hero images that are lazy loaded can hurt LCP. Missing image width and height can create CLS. Optimized loading behavior often helps user experience and ranking signals.

Indexing Notes

Search engines can process lazy loading, but important content should still be discoverable quickly and should not rely on fragile or hidden loading patterns.

How to Fix Lazy Loading & Improve Performance

Your result shows a good setup, but some improvements can make your website faster, more stable, and better for SEO. In some cases, images may not appear in the fetched HTML because the site uses JavaScript rendering. Follow the best practices below to ensure proper lazy loading and strong Core Web Vitals.

  • Use lazy loading only for below-the-fold images
    Example:
    <img src="image.jpg" loading="lazy" alt="Image">
  • Do NOT lazy load your hero (main) image
    Example:
    <img src="hero.jpg" loading="eager" fetchpriority="high" alt="Main Image">
  • Add width and height to all images (fix CLS)
    Example:
    <img src="image.jpg" width="600" height="400" loading="lazy">
  • Use responsive images for better speed
    Example:
    <img src="image-600.jpg" srcset="image-300.jpg 300w, image-600.jpg 600w" sizes="100vw" loading="lazy">
  • Use modern formats like WebP or AVIF
    These reduce file size and improve loading speed significantly.
  • If using JavaScript lazy loading, add fallback
    Example:
    <noscript><img src="image.jpg"></noscript>
  • Ensure images are visible in rendered HTML
    Search engines and tools should be able to detect your images properly.
  • Check performance using real tools
    Use Google PageSpeed Insights or Lighthouse to verify LCP, CLS, and loading behavior.

Important: If no images were detected, your site may be using dynamic rendering. Always verify the live rendered page to ensure images load correctly and are optimized.

How to Read the Results

A good lazy loading setup usually loads below-the-fold images later, keeps important above-the-fold images available immediately, includes width and height on images, and avoids delaying the main visual content of the page.

Best practice:

Use loading="lazy" for content farther down the page, but do not apply it to the primary hero image or other key LCP candidates.

  • High score: Good signals for lazy loading, image sizing, and performance structure.
  • Medium score: Some optimization exists, but there are risks or missing improvements.
  • Low score: Missing lazy loading, possible hero image issues, missing dimensions, or other performance gaps.

Lazy Load Checker FAQ

What does this lazy load checker test?

This tool checks for image and iframe lazy loading, missing width and height attributes, possible hero image lazy loading risks, srcset and modern format signals, noscript fallback usage, and general page-source patterns related to performance and SEO.

Should I lazy load all images?

No. Below-the-fold images are good candidates for lazy loading, but important above-the-fold visuals and hero images usually should not be lazy loaded because they can affect LCP and user experience.

Why does missing width and height matter?

Missing dimensions can cause layout shifts while images load. That can hurt CLS and create a poor experience on both mobile and desktop devices.

Why can some websites fail in this checker?

Some websites block browser-based fetch requests or public proxy access. This tool uses multiple fetch attempts, but some sites may still restrict access.

Can this replace Lighthouse or PageSpeed Insights?

No. This is a practical front-end source checker. It is useful for quick lazy loading reviews, but it is not a full rendering engine or a replacement for Lighthouse, PageSpeed Insights, or server-side crawling tools.