What icons should I create for my website in 2020?

I have been making websites for many years now, and have always created a favicon.ico.

But over the years many other "standard" icons have appeared, for mac, for windows, for android, for iphone, etc, etc, etc.

Personally I have always ignored them ... but maybe it is appropriate to put at least some?

But which ones are worth putting on?
What size and format?
How should they be called? (filename, like favicon.ico)
Where to put it? All in the root?

To have them or not, will it affect the SEO and search engine indexing of a website?

Solution

From a technical point of view, a single SVG icon would be a good thing. I you want you can target each platform individually:

iOS Safari - https://developer.apple.com/library/content/documentation/AppleApplications/Reference/SafariWebContent/ConfiguringWebApplications/ConfiguringWebApplications.html

Android Chrome - https://developers.google.com/web/fundamentals/web-app-manifest/

Edge and IE 12 - https://learn.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/dn320426(v=vs.85)

Desktop browsers -

<link rel="icon" type="image/png" sizes="32x32" href="/icons/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/icons/favicon-16x16.png">
<link rel="shortcut icon" href="/icons/favicon.ico">