It is perfectly normal and expected that you will have less than 100% sent for your web push notifications.
Web Push Notifications resonate with the quick and real-time distribution of brand name interactions. Usually, there are circumstances where not all customers obtain the alerts you send out or schedule for sending out.
Here are the reasons that your delivery rate might be under 100%.
1) The internet browser is closed on the device
Web Notifications appear on a customer's display (on both desktops and also mobile web browsers) when the web browser is open. This indicates that even if your subscriber is surfing various other sites, they will certainly obtain your notifications. But, if the internet browser itself is closed, they will only obtain your notice when they reopen it.
2) Users clear other website data in Chrome
When customers clear various other website data from Chrome, the service workers are uninstalled. With this, your website will not have the ability to send out notifications to that particular subscriber, resulting in a lower delivery rate.
3) The customer disables background Application activity
People are able to switch off background refresh for apps. One factor could be to conserve the mobile battery usage. As well as this can additionally forcefully disable the Chrome or Firefox Application.
4) Network troubles break the connection between GCM and the user
Many times, users are not connected to the internet for a very long time. The factors could be several, from remaining in locations without network protection to staying clear of roaming fees. When this happens, the tool sends heartbeats at a period of 28 minutes on the mobile phone network and also 15 minutes on WiFi (GCM's idle socket connects an Android device to the Google servers).
If this heart beat does not reach the GCM web server, Google continues to re-attempt the connection. If the press notification individual is disconnected from the internet for a lengthy duration, GCM can neither provide the notices nor mark them as inactive. This can either postpone the distribution of the notifications or not supply them entirely.
5) Browser App uninstalled
When a customer uninstalls an internet browser application, there's a delay in GCM tagging that device as non-functioning. This results in the alert being sent out to the GCM, GCM attempting to send it to the gadget, as well as failing at it.