On Android, most notifications are handled by Google Cloud Messaging. The app/site developer pushes a notification to GCM, which then puts up the notification on your device.
The ugly white elephant in the room is that Google sees the text of the notification; it's not e2ee'd. Some more privacy-oriented apps implement GCM such that it just "pokes" the app on your phone to say "hey, check in with us" and the app then fetches the notification text etc. directly. But Google still knows that you got an event from what app.
The ugly white elephant in the room is that Google sees the text of the notification; it's not e2ee'd. Some more privacy-oriented apps implement GCM such that it just "pokes" the app on your phone to say "hey, check in with us" and the app then fetches the notification text etc. directly. But Google still knows that you got an event from what app.