Short practical fixes for things that silently break on small sites.
In our scan of the top 1,500 Tranco domains, 43% of HTML homepages declared no apple-touch-icon and 69% had no web app manifest. Without them, iOS saves a screenshot to the home screen and Android shows a generic letter.
Minimal set that covers almost everything:
<link rel="icon" href="/favicon.ico" sizes="32x32">
<link rel="icon" href="/icon.svg" type="image/svg+xml">
<link rel="apple-touch-icon" href="/apple-touch-icon.png"><!-- 180×180, no transparency -->
<link rel="manifest" href="/manifest.webmanifest"><!-- icons 192 and 512, plus a 512 maskable -->
Keep /favicon.ico at the root even if you declare others; some clients request it blindly. Start from a square source image of at least 512×512.
Free: favicon-audit lists what your homepage declares and whether each loads.
Disclosure: I build Iconpack, a $19 one-time pack that generates the full icon set from your site. Its free check only offers the pack when it confirms the problem on your page. Everything above works without it.