One .ico, every size inside
A proper favicon isn't one image โ it's several resolutions packed into a single .ico container, so browsers, bookmarks, desktop shortcuts and Windows Explorer can each pick the crispest fit. This tool builds exactly that: check the sizes you need (16, 32 and 48 are the classics; 256 covers modern high-DPI cases) and download one file that works everywhere.
Start from a square PNG for best results โ logos with transparency keep it in the icon. The resizing and the ICO container are assembled entirely in your browser, so your artwork never touches a server.
Frequently asked questions
Which sizes do I actually need?
For a website favicon: 16, 32, 48 โ plus 256 if you want it crisp in modern contexts. Windows app icons benefit from the full set.
My source image isn't square โ what happens?
It gets scaled to fit each square size, which may distort proportions. Crop it square first for a clean icon.
Does transparency work in ICO?
Yes โ PNG-based ICO entries keep full alpha transparency in all modern browsers and OS versions.