Favicon rules

Match by domain, http(s)://…, file:///…, or extension filename (e.g. favicon-settings.html). Per rule choose Site default (native favicon; letter only if missing and fallback is on), Custom image, or Letter always. Display name sets the tab title when a rule matches. Save to apply. Open this page with cheese.favicons in the address bar (with or without https://); if the browser sends a search, Cheesefox still opens here.