 How can you get in touch with your users without them having to revisit your website? I'm Sam Dutton, and I'm going to show you how to build engagement with your users and add push notifications to your web app. You might want to be able to provide timely news offers and updates or prompt users to action, for example, to remind a customer to complete a purchase. You want to be able to deliver notifications even when the browser isn't open. You need that process to be trustworthy, fast, and reliable. Now, for many years, this has been possible on native apps and kind of with pretty hacky techniques on the web that tended to use excessive processing and battery. Now, the good news is that push notifications are now possible with built-in JavaScript APIs that are integrated with the underlying operating system. Push notifications make use of two APIs, the notification API to display notifications, and the push API to handle messages that are pushed to the client from your server via the push service used by the browser. This diagram gives an overview. On the back end, you send your messages from your application server to the push service used by the browser, and the push service then forwards messages to the correct user. On the client side, the operating system notifies the browser when a push message is received. Service workers can listen out for push events even when the browser is closed and display a notification. In the next episodes, you'll find out how to send, receive, and display notifications and how to make sure the whole process is secure.