When a user clicks save site to home screen, iPhones will use a 180×180 px PNG file as your site’s icon on the home screen. In fact, you can include this, like a favicon, by adding a link tag in your page HTML head section. You need to set `rel` to `apple-touch-icon` and set `href` together with the path for the icon. Android devices look for a PWA manifest, so work a little differently. First, create two PNG files, one 192×192 px and another 512×512 px. Then just include a manifest file in a link tag (rel="manifest", href="/manifest.webmanifest") in the page HTML head section. Finally, populate the manifest.webmanifest file. This is in JSON format, with an `icons` array at the top level. The two icons are added to this array with src, type (usually `image/png`) and sizes `192×192` and `512×512` defined in an object for each.