PNG compression — Settings and quality

Worked example

For a PNG, the Quality slider has no effect, so the settings that matter are the pixel dimensions and the format you choose to deliver.

The tool draws the image onto a canvas and writes it back as PNG, which is a lossless re-encode. Every pixel and the alpha channel come out the same, and a 1024 × 1024 logo stays 1024 × 1024. Because of that, the result is often only slightly smaller, and if it is not smaller than the original, the tool returns your original file.

To save real weight you have three options. Reduce the pixels by running Resize first, for example 1024 × 1024 down to 512 × 512 when the logo is shown at 256 px on a high-density screen. Convert a flat graphic to WebP, which handles transparency and is usually lighter. Or switch a photograph to JPEG, accepting that transparency becomes white.

Weigh the tradeoffs by content. Logos, icons and screenshots with sharp lines are best kept as PNG when exact edges matter. Photographs stored as PNG are the biggest win from conversion, but a conversion cannot be undone for the pixel data you drop. Resizing costs sharpness only if you shrink below the size at which it is displayed.

In practice, leave the slider where it is, decide the display size, resize to about double that for sharp screens and compare bytes. Only then think about changing format, and keep the PNG master for anything that needs a transparent edge.

PNG logo with alpha

PNG; transparency retained when supported

If you need a certain KB figure, plan on resizing or changing format; PNG alone will not hit a target.