Here is the guide on how to send secret messages on Facebook Messenger in iOS 10. The Secret Conversations feature, as Facebook is calling encrypted chats, means that the message sent can only be read by the sender and the other person from one device - not even Facebook can see it.
How To Set Up And Use Secret Conversations In Facebook Messenger
1) Launch Messenger on your device and click the Me tab at the bottom of the screen.
2) Then click on Secret Conversations.
3) Slide the Secret Conversations switch to the ON position. A popup message will appear saying “This will be the only device you can use to send and receive encrypted messages.”
4) Tap Turn On to enable Secret Conversations on this device.
When you enable Secret Conversations on one device, Messenger will automatically close all secret messages on your other devices.
Secret conversations are currently only available in the Messenger app on iOS and Android, so they won't appear on Facebook chat or messenger.com.
How To Send Secret Messages On Facebook Messenger On iOS 10 iPhone
1) To create a secret message on your iOS 10.0.2 iPhone launch Facebook Messenger and tap the Home tab at the bottom of the screen.
2) Tap the New Message button to start a conversation, then hit the Secret button in the top right and select who you want to message.
Tip: It is possible to tap on an existing conversation, then tap the person’s name at the top and pick Secret Conversation.
3) Now type your message, then hit the Send button.
Secret messages are rendered in black bubbles.
Now you know how to send secret messages on Facebook Messenger in iOS 10, but remember that the recipient could still make a screenshot of the your secret conversation and easily share it with others. So keep that in mind.