A favicon is the small site icon shown in a browser tab, in bookmarks, and on the taskbar. Without one, a tab looks "faceless" — a generic browser icon instead of the site's logo. Making a favicon from an existing image takes about a minute.
What favicon.ico is, and why a plain PNG won't do
The .ico format works in a special way: a single file can contain several versions of the image at different sizes (typically 16, 32, 48, 64, 128, 256 pixels). The browser picks the right size on its own depending on where the icon is shown — in a tab, in bookmarks, or on a "favorites" tile on mobile. If you hand the browser a plain, enlarged PNG, fine details blur once it's shrunk down to 16x16.
How to create a favicon online
Open the favicon generator, upload a square image — a logo or icon — and download the resulting favicon.ico with all the standard sizes packed inside. If needed, you can specify your own list of sizes, comma-separated, in a separate field; leave it blank and the standard set is used. Processing happens on the server, and the file is deleted right after generation.