Image SEO Audit Agent Skill

/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

• Load brand context: Read active brand profile for industry context.
• Discover images: Find all <img>, <picture>, CSS background-image, and <source> elements.
• Alt text audit: Check presence, quality, keyword inclusion, length (10-125 chars). Flag: missing, filename-only ("image.jpg"), keyword-stuffed, non-descriptive ("click here").
• 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).
• 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.
• Responsive images: Check for srcset and sizes attributes, appropriate resolution for device pixel ratios.
• Lazy loading: Verify loading="lazy" on below-fold images. Flag loading="lazy" on above-fold/hero images (directly harms LCP).
• fetchpriority: Check for fetchpriority="high" on LCP/hero images. Check for decoding="async" on non-LCP images.
• 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

| Metric | Status | Count |

|--------|--------|-------|

| Total Images | — | XX |

| Missing Alt Text | issues | XX |

| Oversized (>200KB) | issues | XX |

| Wrong Format (not WebP/AVIF) | issues | XX |

| No Dimensions (CLS risk) | issues | XX |

| Not Lazy Loaded (below-fold) | issues | XX |

| No fetchpriority on LCP | issues | XX |

Prioritized Optimization List

Sorted by estimated file size savings (largest first):

| Image | Current Size | Format | Issues | Est. Savings |

|-------|-------------|--------|--------|-------------|

| hero.jpg | 450KB | JPEG | No WebP, no fetchpriority | ~300KB |

| ... | ... | ... | ... | ... |

Recommendations (prioritized)

• Convert X images to WebP format (est. XX KB total savings)
• Add alt text to X images
• Add width/height dimensions to X images
• Enable lazy loading on X below-fold images
• Add fetchpriority="high" to LCP image
• Compress X oversized images
• 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