Anyone using the Facebook Messenger app now has access to a feature called Secret Messages.

Just like WhatsApp, users will now be able to activate end-to-end encryption, meaning outside sources like the government and even Facebook itself can't read the chats.

The feature was announced back in July but has taken time to roll out to Facebook Messenger's one billion users.

It's pretty much the same method to activate Secret Messages whether you're using an iPhone or Android device. You can see it demonstrated in the video above or use the following step-by-step guide.

Open the Facebook Messenger app and tap the "compose message" icon in the top right of the screen. You should see a list of your contacts and, again in the top right of the screen, the word "Secret" - tap it and select the friend you want to talk to. (Quick note - if you're using an Android phone you'll see a small switch with a padlock instead) The app will ask you to set the phone you're using as your default device - meaning the conversation won't show up on any other phones or tablets you've got linked to your Facebook account. Hit the "Make Default" option to continue You'll now be able to have a conversation that is encrypted end-to-end. You'll know it's secret because Facebook has given the chat window a natty black makeover. If you want to set your messages to self-destruct, click the Set Timer (clock face on Android) and select how long you want the message to remain after it's been read. Just like Mission Impossible.

The Facebook-owned messaging app WhatsApp already encrypts conversations by default, but with Messenger, Facebook is allowing users to choose whether or not to activate the feature.