Which favicon and app icon sizes do you need?
A modern website needs only a handful of icon files. Browsers use a favicon.ico (this generator packs 16×16, 32×32 and 48×48 PNG images into one file) plus PNG favicons for high-density screens. iPhones and iPads use a single 180×180 apple-touch-icon.png when someone adds your site to the home screen. Android and installable web apps (PWAs) read their icons from a web app manifest: a 192×192 icon for the launcher and a 512×512 icon for the splash screen.
What to put in your <head>
Upload the files from the ZIP to the root of your site, then add these tags to every page:
<link rel="icon" href="/favicon.ico" sizes="16x16 32x32 48x48">
<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
<link rel="manifest" href="/site.webmanifest">
The ZIP also contains a ready-made site.webmanifest and a README with the full snippet, including a theme-color tag that matches your background. If your site uses a framework such as Next.js, Astro or WordPress, you can usually drop the files into the public folder (or upload them in the theme settings) instead of writing the tags yourself.
Maskable icons and safe zones
Android shapes launcher icons with its own mask: a circle on one phone, a squircle or rounded square on another. A maskable icon fills the whole square with your background and keeps the artwork inside the central safe zone, so nothing important gets cut off. That's why the maskable and Apple icons in the download are always full squares without transparency: the operating system rounds the corners itself. The shape you choose here (square, rounded, squircle or circle) is applied to the favicon and the regular PNG icons.
Squircle vs rounded square
A rounded square has circular corners that start abruptly. A squircle (a superellipse) curves gradually into its corners, which is the smoother look of iOS app icons. For a letter or emoji logo, a squircle or circle with 15–25% padding usually reads best at tiny sizes; check the 16 px preview before you download, because fine details disappear at that size.