Web push notifications, also known as browser push notifications are messages that are sent from a website to the browser. 
Subscribers will get your notifications even when they are not on your website. 
By combining the Notification and Push APIs with Service Workers we now have another alternative to third-party services (i.e. PushCrew, OneSignal).
With a live practical demo you will learn:
- How to use service workers
- How to integrate Drupal with PHP web push libraries
- How to practically connect web push notifications to a content type
- How to perform metrics on sent notifications (i.e. number of opened/closed notifications by the end user)

https://cluj2019.drupaldays.org/web-push-notifications-campaigns-management-in-drupal