PushCrew tracks unsubscriptions through two ways:
I) Through Google's Firebase Cloud Messaging service
The FCM API sends PushCrew a list of subscriber IDs to which the notifications can no longer be sent.
PushCrew then marks them as Inactive or Unsubscribed in its own database.
II) Through cookies
Whenever a visitor subscribes to your websites’ push notifications, PushCrew stores a cookie file in their browser. This contains a unique subscriber ID for that subscriber.
Every time, the web page that has the PushCrew Smart Code on it, gets loaded, PushCrew looks for this cookie file in the browser, to check the subscriber status. If the user has explicitly denied permission or has set the notification permission to default, the action gets recorded in the cookie file. If PushCrew is able to locate the cookie file and finds the status to be unsubscribed, we mark the subscriber as inactive in our database as well.
However, in the event of the cookie file not being found, primarily because the user had deleted it from their end, PushCrew will mark that user as inactive as well.
You can track your daily unsubscribes, subscribes and total subscribers from the Data & Reporting tab, on the left side of your dashboard panel. The data would look something like the image below.
Date l Subscribes for the day l Unsubscribes for the day l Total Subscribers
III) Ghosting (new)
PushCrew also employs a new technique, called Ghosting, to detect inactive subscribers from the account. Please click here to know more.