Depending on the browser’s favicon parsing, you can do some odd things with it by adding a new <icon> element. I was looking at this the other day and was able to get a basic example of blinking it together (the “What about the favicon?” section from https://alexanderell.is/posts/attention-javascript/).
Re:Don't allow animated favicons (2001)
by dredmorbius on Friday February 04, 2022 @07:25PM
(#30215579)
I swear the more I see of such things the more Gemini appeals.
Principle of minimum privilege and execution.
AFAIU Faviocon was meant to differentiate browser bookmarks and tabs to make it easier to tell which is what.
In March 1999, Microsoft released Internet Explorer 5, which supported favicons for the first time.[4] Originally, the favicon was a file called favicon.ico placed in the root directory of a website. It was used in Internet Explorer's favorites (bookmarks) and next to the URL in the address bar if the page was bookmarked.
https://en.wikipedia.org/wiki/Favicon#History
The fundamental problem is that tabs are already a misfeature of sorts.
https://old.reddit.com/r/dredmorbius/comments/256lxu/tabbed_...