Compress PNG Images

Lossless vs lossy PNG compression

Lossless re-saves the PNG with different filtering and keeps every pixel exactly, then picks the smaller of two encoders. Savings depend on how the original was made: files from screenshot tools and design apps often shrink a little, files already optimized may not shrink at all (the original is then kept).

Reduce colors is lossy: it rebuilds the image with a palette of at most 256 colors and stores it as an 8-bit palette PNG. Most screenshots, icons, logos and illustrations use far fewer distinct colors than they could, so this typically cuts the size by half or more with no difference you can see.

Keeping transparency

Both modes keep transparency, including soft, semi-transparent edges: the palette includes transparency levels as well as colors. Nothing is filled with white or black unless you change Output format to JPG, which can't store transparency. The preview shows transparent areas on a checkerboard so you can see that they survived.

Reducing colors (palette PNG)

Fewer colors mean a smaller file, but smooth gradients and photos start to show bands of flat color. Lower the count step by step and stop when Preview shows banding.

When PNG is the wrong format

PNG is lossless, which makes it large for photographs: a photo saved as PNG is usually several times bigger than the same photo as JPG. If your PNG is a photo with no transparency, set Output format to JPG, or use the PNG to JPG converter. If it is a photo with transparency, WebP keeps the transparency at a fraction of the size, as long as wherever you're putting it accepts WebP.