Compress a PNG to a target size

Why PNG will not simply compress

PNG is lossless. It stores every pixel exactly and squeezes the result with the same general-purpose compression used in zip files. There is no quality dial to turn, because turning one down would mean changing pixels — which is precisely what lossless means it will not do.

So there are only three ways to make a PNG smaller: give it fewer pixels, give it fewer colours, or stop using PNG. This tool uses the first and the third, and reports which one it applied.

When PNG is the wrong format for the job

PNG earns its size on screenshots, logos, line art and anything with sharp edges or transparency. On a photograph it is simply the wrong tool: the same photo as a JPEG is routinely five to ten times smaller with no visible difference.

If your PNG is a photograph, let the format setting stay on automatic. The tool will convert it to JPEG to reach the target and say so in the result line.

Transparency does not survive a conversion

JPEG has no concept of a transparent pixel. When a PNG with transparency is converted, those areas become solid white, which is usually right for a logo on a white page and badly wrong for one placed over a coloured background.

If you need transparency kept, choose WebP as the output format. WebP supports both transparency and lossy compression, so it can reach a small target without flattening the background. Check that whatever receives the file accepts WebP first.

Questions people ask

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