Convert ICO to AVIF

No — that is the whole reason I built this. The conversion runs in your browser using WebAssembly, so your files never leave your device; there is no server in the loop at all. It also means the tool keeps working offline once the page has loaded, and there is no file size limit beyond your device’s memory.

AVIF’s advantage compounds with resolution — a 32px icon is a few hundred pixels of data, where container overhead is a real share of the file and there is little redundancy to exploit. The conversion still makes sense for pipeline consistency; it just will not produce the dramatic percentages larger images do.

Yes — the icon’s alpha channel, hard-edged or anti-aliased, carries into the AVIF unchanged. Small icons with transparency are actually where getting alpha right matters most, since a wrong halo is glaring at 32px.

The primary one your browser hands over when decoding — typically the largest in the file. If your ICO carries a modern 256px entry, that is what you will get; classic favicons yield 32 or 48px.

At 32–48px the formats nearly tie — container overhead swamps codec cleverness, so expect single-digit-KB files either way. Choose by pipeline: if your build already emits AVIF everywhere, consistency wins; if anything downstream is older, ICO to WebP trades a few percent for broader support. For a handful of icons, honestly, flip a coin.

Editing workflows. AVIF at quality 70 re-encodes the icon lossily, so opening, tweaking and re-saving compounds artifacts on an image that is only a few hundred pixels to begin with. Icons you intend to modify should travel through ICO to PNG losslessly; AVIF is a final-destination format, not a working format.