All three are PNG, but they store color differently.

The differences

  • PNG-8 — up to 256 colors, optional 1-bit transparency. Tiny files. Great for flat logos, icons and simple graphics.
  • PNG-24 — millions of colors, no alpha transparency. Photo-quality color, larger files.
  • PNG-32 — PNG-24 plus a full 8-bit alpha channel (smooth transparency). Best for graphics that need soft transparent edges; largest files.

How to choose

Use the simplest one that looks right: PNG-8 for flat icons, PNG-32 when you need smooth transparency. For photographs, PNG is usually the wrong tool — convert to JPG or WebP instead. See also PNG vs JPG.