'ICO or PNG: which favicon format to reach for'

People keep predicting the death of the .ico file, and it keeps not happening. The reason is simple once you see it. An .ico is not really an image format the way a PNG is. It is a container.

What each one is

A PNG is one picture at one size, with good compression and clean transparency. Lovely, and everywhere. An .ico is a small archive that holds several images at once, usually the same icon at 16, 32, and 48. When a browser needs a favicon, it reaches into the .ico and pulls the size that fits the spot.

That difference is the whole argument.

When the .ico wins

Put a favicon.ico at your site root and almost everything understands it, going back to browsers most people have forgotten. It answers the automatic request for /favicon.ico that browsers still fire even when you declare nothing in your head tags. And it carries the small sizes together, so a 16-pixel tab and a 32-pixel bookmark both look right.

For the browser tab, the .ico is still the safe default.

When a PNG is better

Everywhere that is not a legacy tab. A 180-pixel apple-touch-icon is a PNG. The 192 and 512 icons a phone or an installed web app wants are PNGs. Those jobs need one clean size each, and a PNG delivers it with better compression than the same frame stuffed inside an .ico.

So the honest answer is that you use both. The .ico handles the old, small, desktop tab. The PNGs handle phones and app installs. A modern favicon setup is a favicon.ico plus a short stack of PNGs, and that is not a compromise. It is the right tool in each slot.

The practical move

Start from one square image and let the favicon generator build the .ico and the PNGs together. If you have an image and only need the container, the Image to ICO converter on the home page packs your chosen sizes in seconds. Either way, both formats end up in the same setup, each doing the job it is good at.