HTML5 Web Notifications come in two flavors: plain text and HTML. Plain text allows you to customize a couple of parameters, HTML shows any .html file you want as a notification. Notifications are different from regular pop-ups in that they require the user’s permission to be shown. Notice that the request permission dialog only shows after user interaction (e.g. clicking a button). If you’re adding this to a Chrome Extension, just add the ‘notifications’ permission and you’re all set.