Facebook announced a couple of years ago plans to merge all its instant messenger apps into a unified chat system that will allow any user to find and talk to anyone else without requiring an account on the other platforms. In practice, this means Facebook Messenger users could talk to Instagram and WhatsApp users. This idea presented an obvious problem that Facebook addressed right away. WhatsApp is the only Facebook chat app that supports end-to-end encryption by default, while Messenger and Instagram don’t. Mark Zuckerberg said at the time that the unified messaging application would also support end-to-end encryption.
Facebook made a significant step forward last year when Facebook Messenger and Instagram received cross-app messaging support. However, they don’t work with WhatsApp at this time. End-to-end encryption might be the culprit here, and Facebook reconfirmed plans to add the security feature to Messenger and Instagram. However, end-to-end encryption won’t be available on the other apps at least until 2022.