Images account for 75% of page weight on most websites. Unoptimized images are the #1 cause of slow load times and poor Core Web Vitals scores.
This guide explains how to reduce image size without sacrificing quality, helping you boost SEO rankings and user engagement.
Why Optimization Matters#
Google's Core Web Vitals metrics heavily penalize slow visual loading. Large images hurt your Largest Contentful Paint (LCP) score directly.
- Faster Load Times — Better UX, lower bounce rates
- Better SEO — Page speed is a confirmed ranking factor
- Reduced Bandwidth — Save on hosting/CDN costs
- Mobile Friendly — Essential for users on 4G/5G networks
Next-Gen Formats: WebP & AVIF#
Stop using JPEG and PNG for everything. Modern formats offer superior compression:
| Format | Best For | Compression | Browser Support |
|---|---|---|---|
| JPEG | Photos (Legacy) | Lossy | 100% |
| PNG | Transparent Logos | Lossless | 100% |
| WebP | Photos & Graphics | Superior Lossy/Lossless | 97%+ |
| AVIF | High Quality Photos | Best (20% < WebP) | 93%+ |
Choosing Compression Levels#
Compression is a tradeoff between quality and size. For web use:
- Quality 80-85%: Perceptually lossless (best for hero images)
- Quality 60-70%: Standard web usage (thumbnails, blogs)
- Quality < 50%: Noticeable artifacts (avoid unless necessary)
Our benchmarks show that WebP at 75% quality is often 50% smaller than a JPEG at comparable visual quality.
Responsive Sizing#
Never serve a 4000px image to a mobile phone. use the srcset attribute to serve appropriate sizes:
<img src="photo-800.jpg"
srcset="photo-400.jpg 400w, photo-800.jpg 800w, photo-1200.jpg 1200w"
sizes="(max-width: 600px) 400px, 800px"
alt="Optimized photo" />Free Image Compressor
Compress unlimited images to optimum WebP/JPEG levels locally in your browser. No upload limits, no server logs.