Google is removing the inactive and unreachable push subscriptions
Have you noticed an increase in the number of invalid subscriptions that return 404 when you send a notification? That can be related to a recent change in the Chrome push service.
Articles about web push notifications
How to unsubscribe a user from web push notifications
There are different strategies that you can use to allow a user to opt-out from the push notifications of a website that they have previously enabled.
Push API: the PushSubscription object explained
A "push subscription" represents a subscriber to the push notifications of a website.
Difference between PushManager subscribe and getSubscription
These two methods defined by the Push API are used to get the push subscription from the browser. What is the difference between them?
Web Push: how to check if a push endpoint is still valid
How can you verify that a push subscription is still valid (and not invalid or expired)? How can you detect if a user has unsubscribed and the subscription is no longer valid?
Web Push Notifications: store the subscription in the backend / database
When a user is visiting your website and subscribes to notifications, you get a push subscription, which must be stored somewhere (in a database) in order to send notifications to that user.
Web Push: what is an endpoint?
If you are implementing web push notifications on a website you should be familiar with the concept of endpoint.