Compress PNG for Web

On a modern site PNG should be carrying a specific and fairly narrow load: logos, icons, UI screenshots, diagrams, and anything that needs a transparent background. Everything photographic belongs in JPEG or WebP. Sites that fail their performance budget on images are usually shipping photographs as PNG, and no compression setting rescues that — the fix is a format change, not a palette change.

For the assets that genuinely should be PNG, 128 colours with dithering is close to a universal answer. Interface elements and brand marks are built from a small deliberate palette, so halving the available colours removes redundancy rather than information, and the result is pixel-identical to the eye at roughly half the bytes.

For a logo or icon that exists as vector artwork, SVG beats any raster format outright: a few hundred bytes of markup, sharp at every zoom level and on every display density, and styleable with CSS. If you have the original vector file, use it. PNG is the fallback for when you do not, or for artwork with effects that do not survive vectorisation.

WebP supports transparency too and is usually smaller than PNG for the same content, with support in every current browser. The reason to still ship PNG is compatibility with software outside the browser — email clients, older design tools, and anything a colleague might open the file in. For assets that only ever render on your own pages, WebP is the better default and this tool has a converter for it.