As sure you have already noticed if you are a WhatsApp user, there is no official way to avoid notifying who sends a message that your recipient has read it. At most we can disable notifications for both, but we will not see if our interlocutor is receiving our messages. We say "official form" because if you have an iPhone you are lucky. Thanks to the preview of messages on the lock screen we can see the messages received on WhatsApp without alerting the other person that we have actually received and read it.
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Since the incorporation of 3D Touch, and now with its adaptation in the new generations with Haptic Touch, when we receive a notification on our iPhone we can access it from the lock screen, simply by pressing and holding it Until it opens. Simple right? In this way we can even answer messages without even opening the conversation in the application. And therefore, we avoid notifying that we have received and opened anything sent to us.
This "trick" is extensible to all Apps, since Just as we receive a notification of some kind, either by sliding on it or holding down the iPhone, we offer several actions We can do without even unlocking our device.
By holding down a notification we can access more content from it, such as a complete message on WhatsApp.
Also If we slide over a notification almost to the end, we will see that a new option appears that says “Manage”. This pestaa was included in iOS 12 to manage how we want the iPhone to inform us of new notifications. If we want it to be with a conventional and visible notification as well as we wake up the screen of our device, or if on the contrary we want not to be notified on the screen immediately, but that the notification accumulates in the Notification Center for more late. A great idea to avoid accumulating dozens of app notifications that may not interest us immediately no?