Google in 2016, showcased to the public its new App Preview Messaging service within Allo. This service lets users receive messages from third-party services even when the app isn’t installed on the user’s smartphone. The same feature showed up on Duo last month, and as per a report on 9to5Google, it seems as if it’s Google Photos’ turn now.
Too confusing? Ok, let me explain. You can send your friend a message on Allo, and even if your friend doesn’t have Allo installed on his/her smartphone, they will still receive the message. Your friend can then also natively reply through that notification itself, without downloading the app.
The App Preview Messaging service has been integrated into the Play Services by Google. Hence, it is available on majority of Android devices. Users can also receive video and reply to that video with the help of this service. The developer API for this feature for Google Photos is still in preview as per the report on 9to5Google.
When this feature moves out of beta, if a user shares an image or video with you on Google Photos, a dialogue box will let you know that a user has shared an image/video without opening the app. If you click on the notification, a large preview panel of the image will open up. If it’s a video, it will start playing in the large preview panel. From this preview panel, you can also open up the full Google Photos app if you desire.
If you don’t want to receive these notifications, you can simply disable this functionality from the Play Services settings.