Image Optimisation Checks

Identify oversized, unoptimised, and poorly formatted images on your site.

Image Optimisation Checks

Images are typically the largest assets on a web page. LemWatch scans your pages and identifies optimisation opportunities.

What Gets Checked

Check — Description —

Oversized images — Images served at dimensions much larger than displayed —

Unoptimised formats — Images using PNG/JPEG when WebP or AVIF would be smaller —

Missing dimensions — Images without width/height attributes (causes layout shift) —

Total page weight — Combined size of all images on the page —

Lazy loading — Whether off-screen images use loading="lazy" —

Results

For each page checked, you'll see:

• Total images found on the page
• Oversized count — Images that could be resized
• Unoptimised format count — Images not using modern formats
• Total size in KB and potential savings in KB
• Per-image details — URL, current format, dimensions, and recommended changes

How to Fix

LemWatch provides actionable recommendations:

1. Convert to WebP/AVIF — Modern formats are 30–50% smaller
2. Resize to display dimensions — Don't serve 4000px images in 400px containers
3. Add width and height — Prevents Cumulative Layout Shift (CLS)
4. Enable lazy loading — Defer off-screen images
5. Use a CDN with auto-optimisation — Cloudflare, Imgix, or Cloudinary

Impact on Core Web Vitals

• LCP — Large unoptimised hero images directly increase Largest Contentful Paint
• CLS — Missing dimensions cause layout shifts as images load
• INP — Heavy images can block the main thread during decode