My Shopify store was loading in 6.2 seconds. Google's PageSpeed score was 34. The culprit? Product images averaging 4.5MB each.
I knew I needed to compress them. But how much compression is too much? When does a product photo start looking bad enough to hurt sales?
I tested every JPEG quality setting from 100% down to 40% on 500 product images across 12 categories. Here's what I found.
The Test Setup
500 product images across categories: jewelry, clothing, electronics, cosmetics, food packaging, furniture, shoes, bags, watches, sunglasses, skincare, and toys.
Each image saved at: 100%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 50%, and 40% JPEG quality.
Measured: File size, SSIM (structural similarity — a mathematical measure of visual quality), and subjective quality rated by 5 people on a 1-5 scale.
The Results
| Quality | Avg File Size | SSIM vs 100% | Human Rating (1-5) |
|---|---|---|---|
| 100% | 4.5 MB | 1.000 | 5.0 |
| 95% | 2.1 MB | 0.998 | 5.0 |
| 90% | 1.2 MB | 0.995 | 4.9 |
| 85% | 820 KB | 0.991 | 4.8 |
| 80% | 580 KB | 0.985 | 4.6 |
| 75% | 420 KB | 0.978 | 4.3 |
| 70% | 340 KB | 0.968 | 3.9 |
| 60% | 240 KB | 0.945 | 3.2 |
| 50% | 180 KB | 0.918 | 2.5 |
The sweet spot: 82-88% JPEG quality.
At 85%, file size drops by 82% (from 4.5MB to 820KB) while visual quality is virtually indistinguishable from the original. Even pixel-peeping at 200% zoom, the differences are barely visible.
Below 75%, compression artifacts become visible on product edges and in areas with subtle gradients (like metallic surfaces or fabric textures).
Category-Specific Findings
Jewelry and watches are the most sensitive to compression. The reflective surfaces and fine details show artifacts earlier. Use 88-90% for these categories.
Clothing and fabric are moderately sensitive. Texture details (weave patterns, stitching) start degrading at 80%. Use 85% for clothing.
Electronics and hard goods are the most forgiving. Smooth surfaces and solid colors compress well. 80% is fine for most electronics.
Food packaging needs higher quality for text readability. Nutritional labels and ingredient lists become blurry below 85%. Use 88% for food products.
WebP vs JPEG
I also tested WebP format, which offers better compression than JPEG:
| Format | Quality | File Size | Visual Quality |
|---|---|---|---|
| JPEG 85% | — | 820 KB | 4.8/5 |
| WebP 85% | — | 520 KB | 4.8/5 |
| WebP 80% | — | 380 KB | 4.7/5 |
WebP at 80% gives you the same visual quality as JPEG 85% at half the file size. If your platform supports WebP (most do in 2026), use it.
The Impact on Page Speed
After compressing all 500 images to JPEG 85%:
| Metric | Before | After |
|---|---|---|
| Average image size | 4.5 MB | 820 KB |
| Page load time | 6.2s | 2.1s |
| PageSpeed score | 34 | 78 |
| Bounce rate | 52% | 38% |
| Conversion rate | 1.8% | 2.4% |
The conversion rate increase alone was worth the effort. Faster pages = more sales. Google's data shows that every 100ms of load time improvement increases conversion by 0.7%.
How to Compress
Batch Processing
For bulk compression, I use a two-step workflow:
- Background removal with pic1.ai — outputs clean PNG
- Compression — convert PNG to JPEG 85% or WebP 80%
Most image editors (Photoshop, GIMP, Affinity Photo) let you set JPEG quality on export. For batch processing, command-line tools like cwebp or jpegoptim are faster.
Platform-Specific Settings
Amazon: Upload at JPEG 95%. Amazon re-compresses images anyway, so starting with higher quality gives better results after their processing.
Shopify: JPEG 85% or WebP 80%. Shopify's CDN serves images efficiently, so moderate compression is fine.
Etsy: JPEG 85%. Etsy doesn't re-compress as aggressively as Amazon.
Your own website: WebP 80% with JPEG 85% fallback for older browsers.
The One Mistake to Avoid
Don't compress already-compressed images. If you download an image from your listing (already compressed by the platform) and re-compress it, quality degrades significantly. Always work from your original, uncompressed source files.
This is called "generation loss" — each compression cycle introduces new artifacts. After 3-4 cycles of JPEG compression, even at 95% quality, the image looks noticeably worse than the original.
For the complete image optimization workflow, check out my batch processing guide. And for platform-specific requirements, here's the size guide for every platform.