Rollpie Favicon is a free favicon generator that runs in your browser with no install. Upload a single image and it creates the whole set of favicons your website needs, ready to download as a ZIP.
Drag and drop an image onto the area in the center, or click it to choose a file. Transparent PNGs are supported as well.
Under “Fit”, switch between crop, fit, and drag, and set the size with the zoom. Under “Background”, choose transparent, white, or any color you like.
Check how the icon looks in a light and a dark tab in the preview on the right, then save the ZIP from “Export”. It contains the PNGs for every size, favicon.ico, site.webmanifest, and a snippet with the link tags.