Lossy vs. Lossless Compression: A Plain-English Guide
Image formats use one of two kinds of compression, and some, like WebP and AVIF, offer both. Knowing which is which tells you exactly when to use PNG, JPG, or WebP.
Lossless: nothing is thrown away
Lossless compression shrinks a file by storing it more efficiently, with zero loss of detail — like packing a suitcase neatly. Unzip it and you get back exactly what went in. PNG works this way. The trade-off is that there’s a limit to how small a detailed image can get without losing anything.
Lossy: throw away what you won’t miss
Lossy compression goes further by permanently discarding detail the human eye is unlikely to notice — subtle colour shifts, fine texture in shadows. JPG works this way, which is why it makes photos so much smaller than PNG. The trade-off is that the loss is permanent, and pushing it too hard creates visible artifacts.
| Lossless (PNG) | Lossy (JPG) | |
|---|---|---|
| Detail kept | All of it | Most of it |
| File size | Larger | Much smaller |
| Best for | Graphics, text | Photographs |
| Re-saving | Safe | Degrades |
WebP does both
WebP can operate in either mode — lossless for graphics, lossy for photos — which is why it’s such a flexible modern format. For photos, a high-quality lossy WebP usually looks very close to the original; Google’s tests found lossy WebP files 25–34% smaller than comparable JPEGs.
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