Image compression is the process of reducing image file size while maintaining acceptable visual quality. Understanding the different types of compression and when to use each is essential for building fast, professional websites.
Lossy vs Lossless Compression
- Lossy compression (JPG, WebP lossy, AVIF): Permanently removes some image data. Invisible at typical settings (80–90% quality). Produces the smallest files for photographs.
- Lossless compression (PNG, WebP lossless, GIF): Removes no image data. Preserves every pixel exactly. Better for graphics, text, and images requiring editing.
Compression by Image Type
| Image Type | Best Compression | Target File Size |
|---|---|---|
| Photograph | Lossy JPG or WebP 80–85% | Under 200KB |
| Screenshot with text | Lossless PNG | Under 500KB |
| Logo | SVG or lossless PNG | Under 50KB |
| Illustration | PNG or WebP lossless | Under 300KB |
The Compression Workflow
- Resize to display dimensions first (biggest size reduction)
- Choose the right format for the content type
- Apply lossy compression at 80–85% for photos
- Apply lossless compression for graphics and screenshots
- Verify: view at 100% zoom for quality, check file size
- Upload and test page load speed improvement
The Most Common Compression Mistake
The most common mistake is compressing without resizing first. A 4000×3000px image at 85% quality is still 2–5MB — enormous for a website. Resize first to display dimensions, then compress — this typically reduces file size by 90%+ compared to compression alone.
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