Convert ICO to PNG — Every Size Inside

ICO to PNG in one step

An ICO file is a small container: a directory that lists each image, followed by the images themselves. Modern icons store the 256-pixel image as a complete PNG, while smaller sizes are usually stored as Windows bitmaps with a separate 1-bit transparency mask. This converter reads the directory, copies PNG images out byte for byte (no re-compression, no quality loss) and decodes the bitmaps, including 1, 4 and 8-bit palette icons, 24-bit icons and 32-bit icons with alpha, into PNG with transparency.

Which size should I use?

• 16×16 and 32×32: browser tabs, bookmarks and Windows lists.
• 48×48: Windows desktop shortcuts and Explorer's medium icons.
• 180×180 or 256×256: app icons, Apple touch icons and print. If the icon only has small sizes, enlarge it with the image upscaler rather than stretching it.

Why not just rename .ico to .png?

Renaming does not change the bytes, so the file is still an icon container and most apps will refuse it. Some browsers can display a .ico, but they show only the one size they choose. Extracting each image gives you a real PNG that every editor, website builder and app store accepts.

The layout of the format is documented by Microsoft in its Win32 "Icons" technical article (ICONDIR and ICONDIRENTRY structures). Building a new icon? Use the PNG to ICO converter.