Badging API
The Badging API gives web developers a method of setting a badge on a document or application, to act as a notification that state has changed without displaying a more distracting notification. A common use case for this would be an application with a messaging feature displaying a badge on the app icon to show that new messages have arrived.
In a desktop browser, to see the results of the Badging API, you’ll need to pin this web app to your taskbar or dock. In Edge/Chrome, you can do this from the ... > More Tools menu.