Heavy images slow down your website, degrade your Google PageSpeed score and increase your bounce rate. Compressing images is one of the most impactful optimizations for web performance — and it can be done online, without software.
Image compression can be lossy or lossless. Lossy compression (JPEG, lossy WebP) reduces quality imperceptibly to the eye to achieve 40–80% reductions. Lossless compression (PNG, lossless WebP) optimizes encoding without removing information — 10–30% reduction. WebP offers an average 25–35% additional gain over JPEG at equivalent quality. AVIF offers even more compression but browser support is more recent.
📐 Formula
Compression ratio = Original size / Compressed size | Savings % = (1 - Compressed size / Original size) × 100
📊 Reference table
| Format | Compression type | Typical savings | Transparency | Recommended for |
|---|---|---|---|---|
| JPEG → JPEG opt. | Lossy | 20–60 % | No | Photos |
| PNG → PNG opt. | Lossless | 10–30 % | Yes | Logos, icons |
| JPEG → WebP | Lossy | 25–35 % | Yes | Modern web |
| PNG → WebP | Lossy/Lossless | 26 % | Yes | Universal replacement |
| Any → AVIF | Lossy | 40–50 % vs JPEG | Yes | Recent browsers |
💡 Practical examples
Example 1: heavy e-commerce product photo
4MB photo (camera JPEG) → compressed to 150KB (80% quality). Savings: -96%. Result: 26× faster loading, visually identical quality at standard display size.
Example 2: optimize landing page images
Before: 3 images at 800KB each = 2.4MB. After WebP compression: 3 × 120KB = 360KB. 2MB gain on the page. Direct impact on Google's LCP (Largest Contentful Paint).
Example 3: PNG logo with transparency
A 500KB PNG logo can be losslessly compressed to 120KB with ToolSmartly. No degradation of transparency or edges.