PNG CompressorLossy vs Lossless PNG Compression
What each method does to your image, how much it saves and when to use it.
The short answer
Use lossy compression for almost everything you publish: logos, icons, screenshots and illustrations get 60–80% smaller and look the same. Use lossless when every pixel must stay identical, such as source files you will edit again, pixel art or images used for scientific or legal comparison.
How lossless PNG compression works
PNG is already a lossless format: it stores pixels and compresses them with DEFLATE (the same method as ZIP). Most apps save PNGs quickly rather than tightly. A lossless optimizer such as OxiPNG tries different row filters and compression strategies, removes unneeded metadata and picks the smallest encoding. The pixels are untouched, so the savings are modest: typically 5–30%.
How lossy PNG compression works
Lossy PNG compression uses color quantization. A typical PNG can hold over 16 million colors, but a logo or screenshot uses far fewer that matter visually. The quantizer builds a palette of up to 256 well-chosen colors (alpha included) and maps every pixel to the closest one, with optional dithering to keep gradients smooth. The result is an 8-bit palette PNG that is usually 60–85% smaller, still a normal PNG that works everywhere, with full transparency.
Side by side
| Lossy (quantized) | Lossless | |
|---|---|---|
| Typical saving | 60–85% | 5–30% |
| Pixels identical? | No (visually very close) | Yes |
| Transparency | Kept | Kept |
| Best for | Web, apps, email, docs | Editing masters, pixel art |
| Weak spot | Photos with smooth gradients | Big savings are rare |
Which level to pick in our compressor
- Balanced: lossy, tuned for fidelity. The default for most images.
- Smallest: lossy with fewer colors, for thumbnails and flat graphics.
- High quality: lossy with more colors and dithering, for gradients and product shots.
- Lossless: OxiPNG only, every pixel identical.
Try them on your own file with the PNG compressor and compare the result with the before/after slider.
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