So App Badging API is already coming to browsers. It is only available for installed Progressive Web Apps (PWA, for short), the same app badging that already been in mobile apps for years, but now also available for Windows and macOS. It is Google led feature so expect it to works mostly on Chromium browser like Chrome (v81) and Edge (v84). Currently, there are no novel sites that implemented this feature. But you can try it and see whether it works for you by following this demo made by Chrome dev team: Using Chrome 81 or later (or Edge 84) on Windows or Mac, open the App Badging API demo. When prompted, click Install to install the app, or use the Chrome menu to install it. Open it as an installed PWA. Note, it must be running as an installed PWA (in your task bar or dock). Click the Set or Clear button to set or clear the badge from the app icon. You can also provide a number for the Badge value. Official links: https://web.dev/badging-api/ https://github.com/w3c/badging/blob/master/explainer.md https://www.chromestatus.com/feature/6068482055602176 https://w3c.github.io/badging/ Edit: Mozilla confirmed they'll work on this for Firefox browser. https://github.com/mozilla/standards-positions/issues/108
That sounds cool, though I expect it to somehow be used as a tool by advertisers like with desktop push notifications... Hopefully that practice will be regulated against if it hasn't been already.
This only works on PWA that users choose to install themselves. The PWA also must be attached to taskbar either by opening the PWA as an app or pinning them to taskbar, so abuse by advertisers like in push notifications is unlikely. I tried the demo and it works, somehow. The badging shows when I opened the PWA, but gets removed if I close it. The public explainer explains that the badging should be shown even when the web apps are closed since the service workers also can access the API in the background. Either the demo is bugged or the API isn't completed yet--it's unclear since even MDN hasn't yet documented this API.