It’s a question I often ask myself (: Since I work with Webflow I generate a .ico file and feed the dashboard.
If you want to do more, be sure you have these files:
ICO favicon.ico (32x32)
PNG favicon.png (96x96)
Tile Icon tileicon.png (144x144)
Apple Touch Icon apple-touch-icon-precomposed.png (152x152)
You also have generators like this one: http://realfavicongenerator.net/
They output even more details favicons:
<link rel="apple-touch-icon" sizes="57x57" href="/apple-touch-icon-57x57.png">
<link rel="apple-touch-icon" sizes="60x60" href="/apple-touch-icon-60x60.png">
<link rel="apple-touch-icon" sizes="72x72" href="/apple-touch-icon-72x72.png">
<link rel="apple-touch-icon" sizes="76x76" href="/apple-touch-icon-76x76.png">
<link rel="apple-touch-icon" sizes="114x114" href="/apple-touch-icon-114x114.png">
<link rel="apple-touch-icon" sizes="120x120" href="/apple-touch-icon-120x120.png">
<link rel="apple-touch-icon" sizes="144x144" href="/apple-touch-icon-144x144.png">
<link rel="apple-touch-icon" sizes="152x152" href="/apple-touch-icon-152x152.png">
<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon-180x180.png">
<link rel="icon" type="image/png" href="/favicon-32x32.png" sizes="32x32">
<link rel="icon" type="image/png" href="/android-chrome-192x192.png" sizes="192x192">
<link rel="icon" type="image/png" href="/favicon-96x96.png" sizes="96x96">
<link rel="icon" type="image/png" href="/favicon-16x16.png" sizes="16x16">
<link rel="manifest" href="/manifest.json">
<link rel="mask-icon" href="/safari-pinned-tab.svg" color="#5bbad5">
<meta name="msapplication-TileColor" content="#da532c">
<meta name="msapplication-TileImage" content="/mstile-144x144.png">
<meta name="theme-color" content="#ffffff">
That post explains most of it: GitHub - audreyfeldroy/favicon-cheat-sheet: Obsessive cheat sheet to favicon sizes/types. Please contribute! (Note: this may be in flux as I learn new things about favicon best practices.)
Now there’s also the new Safari favicons for pinned tabs. WF doesn’t support it yet.
https://developer.apple.com/library/prerelease/mac/releasenotes/General/WhatsNewInSafari/Articles/Safari_9.html#//apple_ref/doc/uid/TP40014305-CH9-SW20
Pinned sites allow your users to keep their favorite websites open, running, and easily accessible.
You can set the pinned tab icon for your site by providing a vector image. Use an SVG image with a transparent background and 100% black for all vectors. Add the following markup to all your pinnable webpages, replacing “website_icon” with your own file’s name:
<link rel="mask-icon" href="website_icon.svg" color="red">
In the example, the color attribute sets the display color of the image. That attribute can specify a single color with a hexadecimal value (#990000), an RGB value (rgb(153, 0, 0)), or a recognized color-keyword, such as: red, lime, or navy.