For those unfamiliar with how end-to-end encryption works, basically the keys to decrypt the message are on the device of both parties. This means that only when the message reaches its intended recipient does it become decrypted, so even if it were to be intercepted in transit, the attacker wouldn’t be able to read it.
Facebook adds, “We’ll begin testing end-to-end encryption for group chats, including voice and video calls, for friends and family that already have an existing chat thread or are already connected. We’ll also begin a test for your delivery controls to work with your end-to-end encrypted chats. That way, you can prevent unwanted interactions by deciding who can reach your chats list, who goes to your requests folder, and who can’t message you at all.”
What’s interesting about this is that earlier this year, Facebook announced that end-to-end encryption for messages sent on Messenger might not arrive until 2022, so it’s odd that they’ve managed to enable it for videos and audio but not messages. However, to be fair, Facebook did introduce secret conversations and vanish mode a while back that offer similar functionality, but it’s something that users will need to enable.
This is versus Facebook’s other platforms like WhatsApp that have end-to-end encryption enabled by default so users don’t need to do anything on their end.