I am trying to implement the web-push service in one of my projects. So, I actually need to know the actual subscriber numbers in my app. So what problem I am facing is, the service worker generates new endpoints for the same user and I didn't find any unique thing by which I can figure out if the subscriber exists or not.

All my users are also guest users so I don't have any unique thing. There is also an event called onPushSubscriptionChange which doesn't also work in other browsers except for Mozilla.

So is there any way to uniquely identify a user? Like if multiple endpoints are created for the same user then I want to replace the old endpoint with the new one in my database. I am not willing to use cookies also.

Another thing is does firebase cloud messaging solves this issue?

Thank you