Ten days ago WhatsApp got Disappearing Messages
Vanish Mode is activated with a swipe from the bottom of the chat. Once a message is sent, it will stay on the screen until it is turned off or the app is switched. Of course, you can always screenshot the message before it disappears.
The new feature will work both in group chats and personal conversations. While they are instantly disappearing, Facebook revealed conversations can be reported, meaning they will remain in the system for up to 14 days, so they are not instantly deleted.
Such features aren't entirely new in the Facebook universe – there still is “Secret Conversation” for Messenger but it is rather tedious to set up and use and nobody has the time for that. Instagram also has something of a disappearing feature – currently, photos can be sent and set up to disappear once seen but nothing on messages unless you Unsend them.