HTML  

Fav Icons make identifying Web Apps clear in Browsers, Bookmarks, and saving to the Home screen. Generating Icons is easy!

First create an image file for your icon that's large. It should be square and at least 512px by 512px. Going larger is good like 1024 by 1024 so you can regenerate the icons in the future as devices demand larger images.

There are many tools that can create icons for you where you just upload your image and get back some html and several image files in different formats.

One free service is https://iconifier.net, shown below.

Along with the icons, you'll also receive the HTML to be placed between the HEAD tags. The HTML looks like this:

Super easy!!!