Google deprecates its App Preview Messaging feature occasionally used by Photos and Duo
When Google introduced Allo in 2016, the company also detailed a feature for developers of messaging apps known as App Preview Messaging. This feature was aimed at allowing users to send a message from their favorite messaging app to any contact in their phonebook (provided both the sender and the recipient are using an Android device), even if the recipient of the message doesn’t have the app installed. So, say you try starting a Duo video chat with a friend. If your friend doesn’t have Duo installed on their Android phone, they’d get a notification prompting them to download it thanks to App Preview Messaging. The feature is even set up to give users the ability to reply to the message without installing the app! Google employed this feature in Allo (which no longer exists), Duo, and Photos to get people to sign up for these services.
Unfortunately, the feature seems to have fallen by the wayside, never graduating from early access despite Google’s promises to open it up. It’s unclear if any non-Google app ever used the feature in the first place. Regardless, Google recently updated the developer documentation for App Preview Messaging to announce that the early access program has ended and the feature is being deprecated (via AndroidPolice). The page now says that, “as of Q3 2020, this program is complete, and users can no longer send messages with App Preview Messaging.”
Users have always been able to turn off App Preview Messaging in Settings > Google > Data & messaging or block these notifications entirely. Now that the early access period is complete, though, these user settings will be removed from Google Play Services. Google recommends developers turn to Business Messages as an alternative.