Favicon sizes
Cropped in your browser · your image is never uploaded
A 32 × 32 for the tab, a 180 × 180 Apple touch icon, a 192 × 192 and a 512 × 512 for Android and PWA installs. That set covers essentially every modern browser and device.
How to use the favicon sizes
The historical advice to ship a multi-resolution .ico file is largely obsolete: modern browsers happily take a PNG, and an SVG favicon works in most of them and scales perfectly. What has not changed is that 16 and 32 pixels are genuinely tiny: a full logo will not survive, and the icons that work are a single letter, a single shape or a strong silhouette. Design at 32 first and scale up, rather than shrinking a logo down and hoping. The Apple touch icon is the one that must not have transparency: iOS composites it onto a black background, which turns a transparent PNG into a dark square.
Questions
32 × 32 for the tab, 180 × 180 for Apple touch, and 192 and 512 for Android and PWA.
Rarely. Modern browsers accept PNG, and SVG works in most and scales perfectly.
iOS composites it onto black rather than honouring transparency. Export it with a solid background.
Usually not. At 16 pixels a logo becomes a smudge. Use a single letter or shape.
The site root works by convention, but any path referenced from a link tag in the head is fine.