ICO
The little file that lives in your browser tab.
Where it came from
ICO dates back to Windows 1.0 (1985) as the format for interface icons. Its defining trick — packing several resolutions in one file — appeared early, because the same icon had to look right at 16×16 in a title bar and 32×32 on a desktop.
On the web it survives as favicon.ico, the one file every site still ships by convention.
How it works
An ICO is a tiny container: a header, a directory of image entries, then the images themselves — historically BMP-with-alpha (DIB), nowadays often embedded PNG for larger sizes.
That's why ICO handling is really container handling: pick the best frame, decode it, done. UWC's parser selects the largest/most colorful frame and writes Vista+ PNG-format icons back.
Convert ICO
Extract any frame from an .ico as PNG, or build a fresh favicon from your logo — handled by hand-written parsers, no external tools.