Last November, YouTube started experimenting with a feature that would allow users to have conversations with others within its mobile app, but it was only available in Ireland and Poland. The feature was rolled out in some European countries in March, and it’s now expanding to more global markets, including the US, the UK, Brazil, and Singapore. You can click here to check the list of countries where it’s available.
In addition to in-app messaging, this feature also lets YouTube users share videos (long-form, Shorts, and live streams). To use the in-app video sharing and messaging feature, you must be at least 18 years old, signed in to the YouTube channel, and have the latest version of the YouTube app installed on your device. It supports Android devices as well as iPhone and iPad.
The messaging feature also allows YouTube users to unsend a message by long-pressing on it and tapping “Unsend.” Moreover, you can delete a conversation (only from your end) and block a user. You can head this way to learn more about how YouTube’s in-app video sharing and messaging feature works.
Source