Lossy compression: smaller files, some data removed
Lossy compression permanently removes image data that human eyes are least likely to notice. The algorithm analyzes the image, identifies areas where detail can be sacrificed, and discards that information to achieve a smaller file.
JPG is the most common lossy format. At quality 100, very little data is removed and files stay large. At quality 60, significant detail disappears but the image often looks acceptable on screen. The removed data cannot be recovered — re-editing a lossy file and saving again compounds the quality loss.
WebP lossy mode works similarly but typically produces files 25–35% smaller than JPG at the same visual quality. AVIF is a newer lossy format that beats both, though tooling support is still catching up.
Lossless compression: smaller files, every pixel preserved
Lossless compression finds more efficient ways to store the same data without removing anything. It is like packing a suitcase more cleverly — everything still fits, but the bag takes up less space.
PNG is the standard lossless format for web graphics. Every pixel value is preserved exactly. The tradeoff is file size: a photograph saved as PNG is often 5–10 times larger than the same photo as JPG.
WebP lossless mode compresses better than PNG, typically producing files 20–30% smaller with identical quality. PNG remains more universally compatible for lossless needs.
Side-by-side comparison
File size: Lossy wins decisively for photographs. A 5MB PNG photo might become 200KB as JPG. Lossless savings are modest — 10–40% for most files.
Quality: Lossless preserves every pixel exactly. Lossy at high settings (85–95%) looks identical on screen but fails under magnification or heavy editing.
Editing flexibility: Lossless files tolerate repeated editing without degradation. Lossy files lose quality each time you save. Always edit from the original, not a compressed copy.
Best formats: JPG and WebP lossy for photos. PNG and WebP lossless for graphics, screenshots, and logos. TIFF lossless for professional print archival.
Decision guide: which compression to choose
Use lossy (JPG/WebP at 75–85%) for: website photos, social media images, email attachments, blog post illustrations, and any photograph displayed on screen.
Use lossless (PNG/WebP lossless) for: screenshots, logos, icons, images with text, graphics with transparency, and any image where sharp edges must stay crisp.
When unsure, start with lossy at 85% quality and compare against the original at 100% zoom. If you see no difference, the lossy version is fine. If edges look blurry or colors band in gradients, switch to lossless or increase quality.
Try both compression types now
The best way to understand lossy vs lossless is to see it yourself. Compress the same image both ways and compare file sizes side by side.
The Image Compressor lets you adjust quality settings with a live preview and size comparison. Switch between JPG (lossy) and PNG (lossless) output to see exactly how each approach affects your specific file.
Open the Image Compressor, upload your image, and experiment with lossy and lossless settings to find the perfect balance for your needs.