The change brings the back-ends of both apps together, meaning that conversations can take place across the two platforms.
Users will be able to control where they receive messages and calls – in their chats, through message requests, or disable the feature entirely.
Instagram users will also be able to make video calls to Messenger users, and visa versa.
The change means that Instagram messages will receive multiple features already available to Messenger users, including a ‘vanish mode’ where messages will disappear after sending, similar to Snapchat, personalising messages with colours, and quick-forwarding.
Custom emoji reactions, animated message effects, targetted replies, and selfie stickers are among the other features coming to the platform.
It will also allow Instagram users to use the Watch Together feature that is available in Facebook Messenger, to view Facebook Watch, IGTV, TV shows, movies, and other content.
Eventually, that will also expand to Instagram’s TikTok-like feature, Reels.
Mark Zuckerberg has in the past suggested that the plan is part of a vision for the future of Facebook as a private social network.
This does not mean that Facebook and Instagram accounts, or inboxes, are merging. Users will still be able to send and receive messages separately if they choose to.
The company has compared the change to separate email inboxes.
“Just like today you could talk to a Gmail account if you have a Yahoo account, these accounts will be able to talk to each other through the shared protocol that is Messenger,” Loredena Crisan, VP of Product Design for Messenger, told Engadget.
“More than a billion people already use Messenger as a place to share, hang out and express themselves with family and friends. That’s why we’re connecting the Messenger and Instagram experience to bring some of the best Messenger features to Instagram”, Adam Mosseri, Head of Instagram, and Stan Chudnovsky, Head of Messenger, wrote in a blog post announcing the change.
However, various commentators have pointed out that bringing the apps together could help improve the fortunes of Facebook amid criticism, and that it would make it harder for regulators to attempt to break the company into its various constituent apps.
Facebook first purchased Instagram because the photo-sharing platform could ‘hurt’ the company, emails from Mark Zuckerberg during an antitrust hearing revealed.
“Once someone wins at a specific mechanism, it’s difficult for others to supplant them without doing something different”, Zuckerberg said.
In time, Facebook says that it will also integrate WhatsApp into the experience, further consolidating its power in the messaging space, according to Techcrunch, although no timeline was provided for when that change would occur.
“Right now, we are focused on cross-app communications Messenger and Instagram. We are still determining how cross-app communications will work with WhatsApp. WhatsApp will continue to remain a separate, end-to-end encrypted app at this time” said Facebook’s Alexandru Voica on Twitter.
When asked how difficult it would be to undo this integration, if regulators felt that Facebook had too much power, the company said it was be a “massive investment from an infrastructure perspective” to set up, meaning its likely it could be challenging to negate.
“The back end systems that we were sitting on top of were not the same. We had to get to a place where they were similar infrastructure. We had to move features and important things over across both Facebook Messenger, as well as on [Instagram] Direct,” Instagram’s head of product, Vishal Shah, told CNN.
Currently, the update is rolling out “in a few countries around the world” but Facebook says that it will expand globally soon.