Quote:Favioli is a browser extension for Google Chrome, Firefox, and compatible browsers, that lets you replace a site's favicon with a custom icon.
Most websites make use of so-called favicons that web browsers like Chrome or Firefox may pick up to display it when the site is loaded in one of the browser's tabs.
The browser does not display anything if a site has no favicon and if you happen to visit a lot of sites without that icon, your browser's tab bar may lack options to distinguish sites easily.
The latter is true especially in Google Chrome which happens to squeeze sites onto its tab bar so that only the site's icon remains visible (until the icons get removed as well and nothing remains visible, and new tabs don't get visually added to the tab bar anymore).

Full reading: https://www.ghacks.net/2018/09/30/custom-site-icons-in-chrome-and-firefox/