Image Optimization Issues

What This Means

Unoptimized images are one of the most common causes of poor website performance. They contribute to slow page loads, poor Core Web Vitals scores, and excessive bandwidth usage.

Impact:

• Slow Largest Contentful Paint (LCP)
• High bandwidth costs
• Poor mobile experience
• Lower search rankings
• Increased bounce rates

How to Diagnose

1. PageSpeed Insights

Run PageSpeed Insights and check for:

• "Properly size images"
• "Serve images in next-gen formats"
• "Efficiently encode images"
• "Defer offscreen images"

2. DevTools Network Analysis

1. Open DevTools > Network tab
2. Filter by "Img"
3. Check Size column for large images (>500KB is concerning)
4. Note format (JPEG, PNG, WebP, AVIF)

3. Lighthouse Audit

DevTools > Lighthouse > Performance audit shows:

• Image optimization opportunities
• Potential savings in KB/MB

General Fixes

1. Resize Images Appropriately

Rule of thumb: Image dimensions should match display size.

2. Use Modern Formats

HTML with fallback:

<picture>
  <source srcset="image.avif" type="image/avif">
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="Description">
</picture>

3. Compress Images

Tools:

• Squoosh - Online, visual comparison
• TinyPNG - Batch compression
• ImageOptim - Mac app
• ShortPixel - WordPress plugin

Target file sizes:

• Hero images: <200KB
• Content images: <100KB
• Thumbnails: <30KB

4. Implement Lazy Loading

<img src="image.jpg" loading="lazy" alt="Description">

Platform implementations:

• Shopify: Built-in lazy loading
• WordPress: Built-in since 5.5
• Custom: Use Intersection Observer

5. Set Explicit Dimensions

Always include width and height to prevent layout shift:

<img src="image.jpg" width="800" height="600" alt="Description">

6. Use CDN with Image Optimization

Many CDNs offer automatic optimization:

• Cloudflare Polish
• Imgix
• Cloudinary
• Shopify's CDN
• WordPress Jetpack

Platform-Specific Guides

Verification

After optimizations:

1. Re-run PageSpeed Insights
2. Check LCP improvement
3. Verify images still look acceptable
4. Test on mobile devices
5. Check bandwidth savings in Network tab

Automated Solutions

For ongoing optimization:

• CDN-based: Cloudinary, Imgix (transform on the fly)
• CMS plugins: ShortPixel, Smush (WordPress)
• Build tools: imagemin, sharp (development)

Further Reading

• LCP Issues
• CLS Issues (related to image dimensions)