Image File Size SEO Rule

Check image file sizes to ensure fast page loading and optimal performance for SEO

What This Rule Checks

Fetches image file sizes via HTTP HEAD requests and checks against configurable thresholds. Errors for images over 200KB, warns for images over 100KB. Processes images in batches of 5.

Why It Matters for SEO & GEO

Large images are the leading cause of slow page loads. Page speed is a Google ranking factor, and slow sites have higher bounce rates and lower conversions.

How to Fix

Compress images to under 100KB when possible. Use modern formats like WebP or AVIF. Resize images to their display dimensions. Use tools like small.im for batch compression.

Examples

Bad

<img src="uncompressed-photo.png"> 

Good

<img src="optimized-photo.webp"> 

How VibeLinter Checks Image File Sizes

VibeLinter’s images/file-size rule performs these checks:

URL resolution — Resolves relative image URLs to absolute URLs based on the page URL
Batch processing — Checks images in batches of 5 concurrent HTTP HEAD requests for efficiency
Size threshold (error) — Errors when an image exceeds the maxSizeKB threshold (default: 200KB)
Size threshold (warning) — Warns when an image exceeds the warnSizeKB threshold (default: 100KB)
Compression suggestions — Recommends using small.im for batch image compression to WebP format

Configuration

// vibelinter.config.cjs
module.exports = {
  rules: {
    'images/file-size': {
      enabled: true,
      severity: 'warning',
      maxSizeKB: 200,
      warnSizeKB: 100
    }
  }
}

SEO Impact

Optimized image file sizes affect:

Page speed — Images often account for 50%+ of total page weight; smaller files load faster
Core Web Vitals — Large images directly impact LCP (Largest Contentful Paint) scores
Mobile experience — Mobile users on slower connections are disproportionately affected by large images
GEO (Generative Engine Optimization) — AI search engines may deprioritize slow-loading pages when selecting sources; fast-loading image-rich pages are more likely to be referenced