Unseen is an app that allows you to view WhatsApp, Telegram, Viber and Facebook Messenger messages without appearing online. This trick will not allow you to reply to offline messages, but only read received messages without others knowing. You can then take your time before answering.

Each time you receive a notification from your messaging apps, you’ll receive an Unseen alert that you can customize with different colors. By clicking on the WhatsApp tab, you can read the message and your contact will only know you read the message when you click Reply in WhatsApp. You will then be redirected to the WhatsApp app and you will be visible again. Side note: the app doesn’t always work properly with groups.
Download Unseen from Play Store below:
If your friends have Unseen, know that even if you don’t get an answer, your messages have most probably already been read.