Some time ago Facebook introduced the “✔ Seen” feature, letting people know when the receiver reads/sees the message. It can be sometime annoying, especially if we are supposed to be doing something else.
Here a quick trick, that just with the use of your smartphone, will let you read a message sent to you without letting the sender know you did. This has only been tested on Facebook for Android, but most likely will also work on other devices.
PROCEDURE: When you get notification of a message check you have also received it on the phone, now disconnect the phone from WiFi and Mobile Data, click on the message and read it, then close it and go back to something else and turn on connectivity again. Facebook mobile app simply pre-downloads the full message content, allowing you to read it without sending the “Seen” notice to its server since you are offline.
The same concept can probably be applied to similar applications as Whatsapp and its “Last seen on”.