/01 Generating a complete favicon set
Modern browsers and devices ask for a favicon in several sizes and formats, not just the single ICO file that used to be enough. This takes one source image and produces the full set, along with the HTML link tags to paste into your head.
Everything is generated in your browser, so unreleased branding never leaves your machine.
/02 Designing something that survives being tiny
A favicon is often displayed at 16 by 16 pixels. Detail that reads perfectly on a full logo disappears entirely at that size, and thin strokes vanish or turn to mush.
Use a simplified mark rather than your complete logo — a single letter, a symbol, or the most distinctive element on its own. Keep contrast strong and test against both light and dark browser themes, since a dark mark on a transparent background becomes invisible in a dark tab bar.
/03 What a favicon is, and every size you need
A favicon is the small icon that represents your site in browser tabs, bookmarks, history, phone home screens and, increasingly, next to your site name in Google search results. One image cannot serve all of those places well, so a favicon generator's real job is producing the full set.
This one creates eight PNG sizes from a single upload. 16 and 32 pixels are the browser tab sizes. 48 and up keep the icon sharp in search results, where Google asks for a square icon at a multiple of 48 pixels. 180 pixels is the Apple touch icon used when someone adds your site to an iPhone home screen. 192 and 512 pixels are the Android and installable web app sizes referenced from a web manifest. It also packs the 16, 32, 48 and 64 pixel versions into a single favicon.ico file for older browsers and tools that request /favicon.ico directly.
/04 Adding the favicon to your site
Upload the files to the root of your site, paste the generated link tags inside the head of every page, and keep a favicon.ico at the root even if you link PNGs, because some browsers, feed readers and crawlers look for that exact path.
Then expect to wait. Browsers cache favicons stubbornly, so an old icon can hang around for days in a normal window; check your change in a private window instead. In Google search results the new icon only appears after Google recrawls your homepage, which can take anything from a few days to a few weeks.