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image-seo-audit

Audit image SEO on a page: alt text, weight, formats, srcset, lazy loading, CLS. "audit our image SEO"

Published by indranilbanerjee ↗indranilbanerjee/digital-marketing-pro

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image-seo-audit

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Use image-seo-audit to audit [URL] at [scope] and deliver a prioritized image SEO report covering alt text, file weight and formats, responsive delivery, lazy loading, and CLS risks.

Required inputs

  • [URL]
  • [scope]

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SKILL.md

name: image-seo-auditdescription: "Audit image SEO on a page: alt text, weight, formats, srcset, lazy loading, CLS. \"audit our image SEO\""argument-hint: "[URL]"user-invocable: true

/digital-marketing-pro:image-seo-audit

Purpose

Perform a dedicated image optimization audit that evaluates all images on a page or site for SEO, performance, and accessibility. Produces a prioritized optimization list sorted by file size impact.

Input Required

  • URL: Page or site to audit
  • Scope: Single page or site-wide crawl (default: single page)

Process

  1. Load brand context: Read active brand profile for industry context.
  2. Discover images: Find all <img>, <picture>, CSS background-image, and <source> elements.
  3. Alt text audit: Check presence, quality, keyword inclusion, length (10-125 chars). Flag: missing, filename-only ("image.jpg"), keyword-stuffed, non-descriptive ("click here").
  4. File size audit: Apply tiered thresholds by image category — thumbnails (<50KB target, >200KB critical), content images (<100KB target, >500KB critical), hero/banner (<200KB target, >700KB critical).
  5. Format audit: Check for modern formats. Recommend WebP (97%+ support) or AVIF (92%+ support) over JPEG/PNG. Check for <picture> element with format fallbacks. Note: JPEG XL restored in Chromium (Nov 2025) but not yet in Chrome stable — monitor, don't recommend yet.
  6. Responsive images: Check for srcset and sizes attributes, appropriate resolution for device pixel ratios.
  7. Lazy loading: Verify loading="lazy" on below-fold images. Flag loading="lazy" on above-fold/hero images (directly harms LCP).
  8. fetchpriority: Check for fetchpriority="high" on LCP/hero images. Check for decoding="async" on non-LCP images.
  9. CLS prevention: Check for width and height attributes or aspect-ratio CSS on all <img> elements. Flag images without dimensions.
  10. File naming: Check for descriptive, hyphenated, lowercase file names vs generic names (IMG_1234.jpg).
  11. CDN usage: Check if images are served from a CDN (different domain, CDN headers, edge caching).
  12. Score and prioritize: Sort by file size savings impact (largest first).

Recommended Picture Element Pattern

<picture>
  <source srcset="image.avif" type="image/avif">
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="Descriptive alt text" width="800" height="600" loading="lazy" decoding="async">
</picture>

Hero/LCP Image Pattern

<img src="hero.webp" fetchpriority="high" alt="Hero image description" width="1200" height="630">

Do NOT lazy-load above-fold/LCP images. Do NOT add decoding="async" to LCP images.

Output

Image Audit Summary

MetricStatusCount
Total Images—XX
Missing Alt TextissuesXX
Oversized (>200KB)issuesXX
Wrong Format (not WebP/AVIF)issuesXX
No Dimensions (CLS risk)issuesXX
Not Lazy Loaded (below-fold)issuesXX
No fetchpriority on LCPissuesXX

Prioritized Optimization List

Sorted by estimated file size savings (largest first):

ImageCurrent SizeFormatIssuesEst. Savings
hero.jpg450KBJPEGNo WebP, no fetchpriority~300KB
...............

Recommendations (prioritized)

  1. Convert X images to WebP format (est. XX KB total savings)
  2. Add alt text to X images
  3. Add width/height dimensions to X images
  4. Enable lazy loading on X below-fold images
  5. Add fetchpriority="high" to LCP image
  6. Compress X oversized images
  7. Implement <picture> element with AVIF/WebP fallbacks

Agents Used

  • seo-specialist — Image optimization analysis, CWV impact assessment

Scripts Used

  • tech-seo-auditor.py — Fetch page and analyze image elements